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When moving to variable inventory management models. Methods and models of inventory management. Static inventory management models

2.3.1. Stock rationing

Inventory management consists of solving two main tasks:

1) determining the size of the required stock, i.e. stock standards and frequency of replenishment;

2) creation of a system for monitoring the actual size of the stock and its timely replenishment in accordance with the established norm.

Stock norm– the estimated minimum level of inventory that must be in the enterprise’s warehouse to ensure uninterrupted supply for production or sales of goods. To determine inventory standards, three groups of methods are used: heuristic methods, methods of technical and economic calculations and economic and mathematical methods.

Heuristic methods involve the use of the experience of specialists who study financial statements for the previous period, analyze the market and make decisions on the minimum required reserves, based, to a large extent, on a subjective understanding of demand trends. An enterprise employee who constantly solves the problem of stock rationing can act as a specialist. In this case, the method for solving the problem is called experimental and statistical. If the experience of several specialists is used at once, then their subjective assessments of the situation are analyzed using a special algorithm, checked for consistency and transformed into a final solution that is close to the optimal one. This method is called the method expert assessments.

Method of technical and economic calculations consists in dividing the total stock, depending on the intended purpose, into separate groups, for example, nomenclature or assortment items. Then, insurance, current and seasonal stocks are calculated separately for these groups. Each of these levels can also be divided into smaller components, for example, safety stock in case of supply disruptions, or safety stock in case of increased demand, etc. Method of technical and economic calculations allows you to fairly accurately determine the required amount of inventory, but is highly labor-intensive. This approach is also used in the MRP system (see clause 7.5.2).

Economic and mathematical methods allow you to determine the stock norm based on the constructed mathematical models of ultrasound, or using extrapolation methods forecast future stock based on the rate of change and trends in formation and stock in the previous period.

The efficiency of KM systems largely depends on how accurately the demand for a resource is predicted and, therefore, how correctly rationing is carried out. This is quite a difficult task. The following types of demand are distinguished according to the degree of certainty and invariability of its value (Fig. 2.3)

Fig.2.3. Classification of demand types

Deterministic demand is precisely known in advance, unlike probabilistic demand. At static type of demand, the intensity of resource consumption remains constant over time, with dynamic type of demand, the intensity of consumption varies depending on time. At stationary type of demand, its probability density function is constant over time, and when non-stationary – The probability density function of demand varies over time.

Based on the source of origin, demand is divided into independent and dependent. Independent demand – demand, which consists of individual components of the demand of a large number of consumers, each of whom experiences a need independently of the others. Dependent demand occurs when a manufacturer uses a number of components to manufacture a GPU, the demand for each of the components is related to each other and depends on the production plan for manufacturing the GPU.

The independent demand type uses an approach in which inventories are not linked to production plans and therefore must be high enough to satisfy any possible demand. These inventories are reduced during production, but are soon replenished again. The general dynamics of changes in inventories with independent and dependent demand are shown in Fig. 1, respectively. 2.4 (a) and (b).

Fig.2.4. Comparison of the dynamics of changes in inventory volumes

with dependent and independent demand

If there is dependent demand, the approach can be used MRP – materials requirements planning(material requirements planning) (see clause 7.5.2). The essence of this approach is to calculate the requirements for all types of materials, raw materials, components, parts necessary to produce each product from the production plan in the required volume, and submit the corresponding purchase orders. The calculations use specification sheets– an ordered list of all the components needed to produce a specific product.

Another planning approach is "right on time"(just in time) or JIT (see clause 7.5.4 ). TargetJIT– ensuring the delivery of materials directly to the time of specific operations, due to which the stock is actually destroyed. In Fig. Table 2.5 presents inventory volumes for various planning approaches.

Rice. 2.5. Inventory levels under different approaches to inventory management

The reason for the decrease in inventory levels shown in Fig. 2.5 (b) and (c), is the increasing coordination between the demand in the sales market and the enterprise’s demand for materials supplied by suppliers.

2.3.2. Static inventory management models

Generalized model of the optimal delivery batch taking into account unfulfilled orders

Model input parameters

1) n – intensity of consumption of the stock [unit/unit t];

2) l – order production intensity [items/unit t];

3) s – costs of storing inventory [RUB/unit of goods*unit t];

4) d – penalty for shortage [RUB/unit of product*unit t];

5) K – costs of ordering [RUB].

Model output parameters

1) Q – order size [item];

2) t – delivery period [unit t];

3) – duration of the i-th stage of the inventory change cycle;

4) L – total costs of inventory management per unit of time, [rub./unit t];

5) N – maximum stock level in the warehouse [items];

6) h – maximum level of shortage [items].

This model is based on the assumption that there is a production process in which a batch of parts with intensity is produced on the first machine, which are used on the second machine with intensity (Fig. 2.6).

Fig.2.6. Schematic diagram of the production process

Unfulfilled requests for a consumable product accumulate and are immediately satisfied as new product arrivals occur. The duration of the inventory change cycle is divided into 4 stages (Fig. 2.7):

1) t 1 – the ordered product is produced, the produced product is consumed ® stock accumulates;

2) t 2 – the ordered product is not produced, the stock is consumed ® the stock is reduced to zero;

3) t 3 – the ordered product is not produced, there is no stock ® unfulfilled orders accumulate, the shortage increases;

4) t 4 – the ordered product is produced, outstanding orders are fulfilled ® there is no stock, the deficit is reduced to zero.

Fig. 2.7. Graph of inventory change cycles in the generalized KM model

taking into account outstanding applications

Model formulas

; ; ;

; ; ; ;

Generalized model of optimal delivery batch with loss of unfulfilled orders

This model is characterized by the fact that during period t 3 the ordered product is not produced, there is no stock, the deficit increases, but at the same time, unfulfilled orders do not accumulate, but are lost (Fig. 2.8). At the same time, the penalty for shortages in the model with the loss of unfulfilled orders is higher than in the model taking into account unfulfilled orders.

Fig. 2.8. Graph of inventory change cycles in the generalized KM model

with loss outstanding orders

Model formulas

; ;

; ; ; ; .

Each of the considered generalized KM models has four possible KM situations:

1) the product is produced (), shortages are allowed () (see Fig. 2.7, 2.8);

2) the product is purchased (), shortages are allowed ();

3) the product is produced (), shortage is prohibited ();

4) the product is purchased (), shortages are prohibited () – Wilson model(Fig. 2.9).

Fig.2.9. Graph of inventory cycles in the Wilson model

KM model taking into account discounts

This model takes into account the possibility of providing discounts to the buyer when purchasing a batch of goods of a certain size. At the same time, orders for larger quantities, on the one hand, will entail a reduction in procurement and delivery costs, and on the other hand, an increase in storage costs. Thus, the optimal order size may change compared to the situation without discounts. A detailed description of the KZ model that takes into account discounts is given in paragraph 12.

2.2.3. Dynamic systems of ultrasound

In real conditions of ultrasound, some parameters may change during a certain planning period for the following reasons:

· change in consumption intensity in one direction or another;

· delay or acceleration of delivery;

· delivery of unplanned order volume;

· errors in accounting for actual inventory, leading to incorrect determination of the order size.

Table 2.1 presents possible disturbing influences that lead the system to a state of either a shortage of MH or warehouse space. In practice, various combinations of impacts listed in the right and left columns of Table 2.1 may occur.

Table 2.1

Possible disturbances in the inventory management system

In the situations described, static KM models do not work, and therefore it is necessary to use dynamic KM models, which provide adaptation mechanism to the changing situation.

Another feature of static KM models, which is unacceptable in the described conditions, is the use of the criterion of minimizing the total costs of storing inventory and delivering orders. This criterion does not make sense in situations where

· order execution time is quite long;

· deliveries are often delayed;

· demand experiences significant fluctuations;

· prices for ordered raw materials, materials, semi-finished products, etc. fluctuate greatly.

In this case, it is not advisable to save on inventory maintenance. This may lead to the impossibility of continuous service to the consumer, which does not correspond to the purpose of the functioning of the KM logistics system. In all other situations, determining the optimal order size ensures a reduction in inventory storage costs without loss of service quality.

TO main Dynamic KM systems include:

1) system with a fixed order quantity;

2) a system with a fixed time interval between orders.

KM system with fixed order quantity

The movement of inventory in a system with a fixed order quantity is graphically presented in Fig. 2.10.

Fig.2.10. Graphic model of the operation of the KM system

with fixed order size

The threshold stock level is calculated as the volume of stock that will be consumed during delivery, taking into account the preservation of safety stock. In the absence of supply disruptions, the order is received when the stock reaches insurance level. Insurance stock allows you to meet the demand for the maximum possible expected delivery delay. The safety stock is replenished during subsequent deliveries. If there are no supply disruptions and the optimal supply size, the stock is replenished to maximum desirable level. Unlike the insurance and threshold, the maximum desired stock does not have a direct impact on the functioning of the system as a whole. This stock level is determined to track space utilization.

The procedure for calculating the parameters of an inventory management system with a fixed order size is generally presented in Table 2.2.

Table 2.2

Parameters of the KM system with a fixed order quantity

	Input parameters	Designation
	Maximum
	Delivery cost, K, rub.
	Output parameters	Calculation
	Optimal order size, pcs.
	Safety stock, pcs.
	Threshold stock level, , pcs.

Necessity permanentstock accounting in a system with a fixed order quantity can be considered as its main disadvantage. In addition, this system is not accounting-oriented repeated failures in the volume of supplies. They can lead it to a scarce state, which can be aggravated by a delay in subsequent deliveries (Fig. 2.11). To correct this situation, it is necessary to require from the supplier disposable increasing the volume of supply, which will allow replenishment of stock to the maximum desired level.

Inventory management system with a fixed time interval between orders

A graphical model of the operation of the KM system with a fixed time interval between orders is presented in Fig. 2.12.

Fig.2.11. Graphic model of the operation of a management system with a fixed order size in the presence of repeated delays in deliveries

Fig.2.12. Graphic model of the operation of the KM system

with a fixed time interval between orders

The procedure for calculating the parameters of the inventory management system with a fixed time interval between orders is presented in Table 2.3. Time interval between orders (delivery period) usually calculated and then can be adjusted. For example, if the estimated result is 4 days, you can use a period of 5 days to submit orders once a week.

The basic KM systems described above are based on fixing one of two possible parameters – order size or time interval between orders. But if available systematic disruptions in supply and consumption, the main KM systems become ineffective.

Table 2.3

Parameters of the ultrasound system with a fixed time interval

between orders

	Input parameters	Designation
	Consumption intensity, , pcs/unit t (when calculating, round up)
	Order delivery time, , unitst
	Maximum possible delay in deliveries, , unitst
	Delivery cost, K, rub.
	Inventory storage cost, s, rub./(pcs*days)
	Output parameters	Calculation
	Delivery period, , units t
	Safety stock, pcs.
	Maximum desired stock, , pcs.
	Order quantity, Q, pcs.
	where is the current stock taking into account the ordered but not delivered goods

Various combinations of parts of the main KM systems, together with the addition of fundamentally new ideas, lead to the possibility of forming a large number of other KM systems that meet a wide variety of requirements.

To the most common modifications The main dynamic systems of KM include:

1) a system with an established frequency of replenishment of stocks to a constant level;

2) the “minimum-maximum” system.

Management system with established frequency of replenishment of stocks to a constant level

A distinctive feature of the system is that orders are divided into two categories:

1) planned Q p, which are supplied at specified time intervals t;

2) additional Q d, when stocks in the warehouse decrease to a threshold level. The need for additional orders may arise if consumption rates deviate from the planned ones.

Thus, this system includes a system element with a fixed time interval between orders (established order frequency) and a system element with a fixed order size (tracking threshold inventory levels). Unlike basic systems, it is focused on working with significant fluctuations in consumption.

A graphic illustration of the functioning of the management system with an established frequency of replenishment of stocks to a constant level is shown in Fig. 2.13. The procedure for calculating all parameters of the ultrasound system in the general case is presented in Table 2.4.

KM system “minimum-maximum”

Fig.2.13. Graphic model of the operation of the management system with an established frequency of replenishment of stocks to a constant level

Threshold stock level in the “minimum-maximum” system plays the role of “ minimum» level. If at a set point in time this level is passed, then the order is issued, otherwise the order is not issued. The threshold level is monitored, as well as the order is issued only after a specified time interval t.

This system works with two levels of inventory - minimal(threshold) and maximum and contains elements of a system with a fixed time interval between orders (constant interval between deliveries) and a system with a fixed order size (use of a threshold level). The “minimum-maximum” system is focused on a situation where the costs of inventory accounting and ordering costs are so significant that they become commensurate with losses from inventory shortages. A graphic illustration of the functioning of the minimum-maximum KM system is shown in Fig. 2.14. The procedure for calculating all parameters of this ultrasound system is presented in Table 2.5.

Table 2.4

Parameters of the management system with an established frequency of replenishment of stocks to a constant level

1. Introduction 2

2. Basic concepts and definitions of logistics as a subsystem of the sciences of enterprise management 3

2.1.

Logistics concept 3

2.2.

Logistics systems, their definition and types 5

2.3.

Place of inventory logistics in the enterprise logistics system 10

3. Inventory logistics 12

3.2.

Types of stocks 14

3.3.

Inventory management systems in companies 17

3.3.1.

General information 17

The warehouse system, which is a subdivision of the logistics subsystem, plays a significant role in the unified functioning of the entire mechanism of the enterprise. The importance of logistics is noted, primarily from the point of view of the internal circulation of material flows, including within the framework of the production process. The stage of preparing a product in a semi-finished state, supply and storage of materials and components for production, all these processes represent the mechanism of the enterprise, regulated by personnel and managers responsible for warehousing logistics and inventory logistics. From the point of view of planning the short-term production of goods by an enterprise, calculating the required level of supply of components to the warehouse, creating the required volume of reserves, choosing the most "convenient" For an enterprise, suppliers are the most important functions of responsible employees of the enterprise. The production output of the enterprise, and partly the profit and competitiveness of the enterprise, depend on the precise performance of these functions by the enterprise’s employees.

It is for this reason that topics and processes related to warehousing logistics and inventory logistics are a very important subject for study by the future manager.

The warehouse system of the enterprise itself, the logistics system as a whole, has a number of key components from the point of view of the functioning scheme.

For example, the most important component of the logistics system is the information subsystem, without which it is impossible to implement the ideas and principles of logistics. It has now been proven that certain connections exist between the functions, structure and information of a system (for example, an enterprise). This position of system analysis is based on the fact that the totality of all information flows connects all functions into a single system. If in a logistics chain the channel through which the material flow moves can be represented as a kind of artery, then the telecommunications information network can be represented as a central nervous system. Information flows are crucial for the functioning of the entire logistics chain, and the principles of information logistics that study them are the basis for the construction of all logistics systems. In a post-industrial economy, also defined as an information society, the special significance of information lies in the fact that it is, first of all, a means of production, as necessary for the functioning of a company as raw materials, labor, capital, and not just a consumer item.

2. Basic concepts and definitions of logistics as a subsystem of the sciences of enterprise management

2.1. Logistics concept

Logistics comes from the Greek word “logistike”, which means the art of calculating, reasoning.

Logistics is the science of planning, organizing, managing, controlling and regulating the movement of material and information flows in space and time from their primary source to the final consumer.

Logistics is divided into several main areas:

Information logistics

Purchasing logistics

Logistics of production processes

Sales logistics

Inventory logistics

Warehousing logistics

Transport logistics

Organization of logistics management

In this work, we plan to consider the inventory logistics section as one of the most important and significant in the activities of a manufacturing company.

The main goal of logistics

The global goal of logistics is to shorten the cycle and reduce inventories.

At the production stage - due to the synchronization of processes; by determining the need for material resources; what is needed? When? How many?; due to self-regulation (production occurs in accordance with the demand for a particular product).

The relationship between different cycles of product creation and production.

T tp =99% SONT T p - production cycle (time for parts to circulate in workshops.

T arr = 5% T tp - cycle of technical training of production (R&D, technical and technological development)

T simple = 95% T arr - processing on machines

T is simple - transportation, storage, downtime

T o =15% T o - main work time

T vsp - auxiliary time

T vsp =70-85%

t=t pcs +tn/n - time reduction formula

The main task of logistics is the use of materials, energy, information, personnel and means of production. Provide the consumer with products at a given time of a given quality in a given place and for a certain price.

Supply logistics - procurement of maximum materials.

Production logistics - find additional storage space.

The product must be sold as quickly as possible: D-T-D’ or D-T-P-T’-D’ (both directly and through an intermediary).

The essence of commodity circulation lies in the combination of physical and economic processes. Physical movement consists of its territorial advancement from one geographical point to another. Movement in economic space consists of the transfer of goods from one owner to another, i.e. in changing the rights of the owner of the goods.

Logistics is the search for a distribution channel that ensures minimum time and minimum costs for delivering goods to the consumer. Ensures continuity of production and reproduction.

Inventory is finished goods that have not been sold.

Product purposes:

Satisfying consumer needs;

Bring profit to the owner;

The sales cycle should be as short as possible. Conditions:

1. Transition from the seller's market to the consumer market;

2. The production of products in large quantities is being replaced by small-scale production.

The main goals of logistics and areas of work for their implementation

The means to achieve the main goal of logistics are the goals of the second level - the main goals that are the nature of the enterprise’s activities in the field of logistics.

Basic goals: 1. Purchasing at minimum prices;

2. Increased supply reliability;

3. Ensuring the synchronization of the processes of supply and processing of materials;

4. Ensuring continuity of the production process;

5. Fulfillment of received orders in terms of range and quality;

6. Minimization of production costs;

7. Adaptation of production to changing demand;

8. Reducing the level of finished product inventories;

9. Satisfy millet consumers;

10. Delivery of products according to orders and contracts;

11. High degree of supply readiness.

Direction of work to achieve logistics goals:

Formation of requests for materials;

Selection of suppliers;

Development of a materials delivery schedule;

Design and organization of the functioning of departments involved in material and technical support of production;

Organization of transportation of materials during the production process;

Organization of delivery of materials to workplaces;

Material flow management in production;

Management of materials inventories in production;

Establishing direct connections with product consumers, forming a portfolio of orders;

Organization of product delivery to consumers;

Organization of customer service;

Organization of storage of finished products;

Finished product inventory management.

The essence of logistics

The main goal of logistics is to deliver industrial products to the right place on time and in the required quantities with minimal costs.

The set of logistics functions and goals determine the essence of logistics.

The essence of logistics is integration, ensuring interaction between stages and participants in the goods distribution process, managing material flows based on accompanying information in order to deliver the necessary goods to the right place at the right time with minimal costs.

The processes occurring in the logistics system and characterizing its interaction with the external environment reveal the content of logistics as a type of practical activity.

2.2. Logistics systems, their definition and types

System concept

The concept of “system” is given the following definition in the encyclopedic dictionary: it is a set of elements that are in relationships and connections with each other, forming a certain integrity, unity.

The approach to the objects of ensuring the distribution of goods to systems expresses one of the main features of logistics, both science and the field of practical activity. Systematic research is a natural necessity of scientific and technological progress, which allows us to combine and use the most progressive and effective methods available to science. When studying any systems, we are faced with the problem of identifying the principles of their construction, functioning, as well as the interaction of systems with the environment.

The system as such is a self-sufficient structure created for a specific purpose by nature or man, consisting of interacting and interconnected elements, which exists relatively independently and sustainably, constantly developing and improving, depending on influences on the environment.

If a natural system ceases to satisfy the goals “set by nature,” it dies, and in its place new, stronger and more viable systems arise. The same can be said about artificial systems created by man for the purpose of improving himself and society.

Any system has a boundary that separates it from the outside world. Many systems have clearly defined boundaries, but there are systems with other unclear boundaries. Of particular interest in this regard are production and economic systems. Their boundaries in production, financial, informational, and social aspects may have significant differences in space and time.

In order for a system to exist, develop, improve and survive in extreme conditions, it must have a set of certain properties.

Integrity and articulation. A system is an integral set of elements interacting with each other. It should be kept in mind that elements exist only in the system. Outside the system, these are only objects that have the potential ability to form a system.

System elements can be of different quality, but at the same time compatible. Connections

. There are significant connections between the elements of the system, which naturally determine the integrative qualities of this system. Connections can be real, informational, direct, reverse, etc. The connections between elements must be more powerful than the connections between individual elements by the external environment, since otherwise the system cannot exist.

Organization.

The presence of system-forming factors among the elements of the system only presupposes the possibility of its creation. For a system to appear, it is necessary to form ordered connections, i.e. a certain structure and organization of the system.

Integrative qualities

.

The system has integrative qualities, i.e. qualities inherent in the system as a whole, but inherent in one of its elements separately.

Logistics system concept

The movement of material flows is carried out by qualified personnel using a variety of equipment: vehicles, loading and unloading machines, etc. Various building structures are involved in the logistics process, the progress of the process significantly depends on the degree of preparedness for it, the most moving cargo accumulated in stocks, the totality of productive forces that ensure the passage of cargo, better or worse, is always somehow organized. Logistics poses and solves the problem of designing harmonious, coordinated material-conducting (logical) systems, with given parameters of output material flows.

These systems are distinguished by a high degree of coordination of the productive forces included in them in order to manage end-to-end material flows. Characterizes the properties of logistics systems in terms of each of the four properties inherent in any system, given in paragraph 1.:

Integrity and division -

a system is an integral set of elements interacting with each other. The decomposition of logistics systems into elements can be carried out in different ways.

At the macro level, when a material flow passes from one enterprise to another, these enterprises themselves, as well as the transport connecting them, can be considered as elements

At the micro level, the logistics system can be presented in the form of the following subsystems:

Purchase– a subsystem that ensures the flow of material into the logistics system.

Production planning and management– this subsystem receives the material flow from the procurement subsystem and manages it in the process of performing various technological operations, transforming the object of labor into a product of labor.

Sales – subsystem that ensures the disposal of material flow from the logistics system ( rice. 2).

Micrological system

a system is an integral set of elements interacting with each other. The decomposition of logistics systems into elements can be carried out in different ways.

At the macro level, when a material flow passes from one enterprise to another, these enterprises themselves, as well as the transport connecting them, can be considered as elements

As we see, the elements of logistics systems are of different quality, but at the same time compatible. Compatibility is ensured by the unity of purpose that underlies the functioning of logistics systems.

Communications- There are connections between the elements of the logistics system that naturally determine integrative qualities. In macrological systems, the basis of the connection between elements is an agreement. In micrological systems, elements are connected by intra-production relations.

Organization - the connections between the elements of the logistics system are ordered in a certain way, that is, the logistics system has an organization.

Integrative qualities - The logistics system has integrative qualities that are not characteristic of any of the elements separately. This is the ability to deliver the right product, at the right time, in the right place, of the required quality, at minimal cost, as well as the ability to adapt to changing environmental conditions.

A logistics system that can respond to emerging demand by quickly delivering the right product can be compared to a living organism. Muscles are lifting and transport equipment, the nervous system is a network of computers at workplaces, organized into a single information system. In size, this organism can occupy the territory of a factory or distribution center, or it can go beyond the borders of the state. He is able to adapt, adjust to disturbances in the external environment, and respond to it at the same pace as events occur.

Types of logical systems

According to the scale of the scope of activity, logistics systems are divided into macro- and micrologistics systems.

The macrological system includes enterprises and industrial organizations, supply and sales structures and transport organizations of different departments in different regions. As such, we can consider transnational corporations, transcontinental firms, regional industrial associations, and territorial production complexes.

The construction of macrological systems and their management contributes to solving such problems as:

• Development of a general concept for product distribution;

  Choosing the type of transport, determining the nature of the interaction of vehicles, organizing the technology of the transport process;

  Determination of rational directions of movement of material flows;

  Selection of delivery points and partner suppliers of raw materials, materials, semi-finished products, energy resources;

  Determining the boundaries of the service area ensuring deliveries on a just-in-time basis;

  Design and organization of a network of warehouse systems: central regional, transshipment, taking into account the optimization of material flows.

The micrological system is built from the standpoint of the strategic goals of companies and the optimization of basic operational processes; it covers the scope of activity of an individual enterprise and provides solutions to local issues within the framework of individual functional elements of logistics systems. According to their functional purpose, mycological systems are divided into first and second level systems.

The micrological system of the first level reflects the logistics of the enterprise, covering both the internal production activities of the enterprise and its external contacts and connections.

The macrological system of the second level reflects intra-production logistics, which integrates the processes of production planning, sales and supply, transport, storage and loading and unloading operations of the enterprise.

At the macro logistics level, there are three types of logistics systems.

Logistics systems with direct connections. In these logistics systems, material flow occurs directly from the product manufacturer to the consumer, bypassing intermediaries.

Echelon logistics systems. In such systems, on the path of the material flow, there is at least one intermediary.

Flexible logistics systems. Here, the movement of material flow from the manufacturer of a product to its consumer can be carried out directly. The same goes through intermediaries.

Among the variety of searches for ways to develop the market, means of production, new areas of activity of commercial intermediary organizations and enterprises, scientific research and practical innovations, united by the concept of logistics, are of significant interest.

In recent years, new logistics technologies based on computer science have been rapidly developing. Information systems occupy a central position in these technologies.

Logistics information systems are divided into three groups:

planned;

dispositive (or dispatch);

executive (or operational).

Logistics information systems included in different groups differ in both their functional and supporting subsystems. Functional subsystems differ in the composition of the tasks they solve. Supporting subsystems may differ in all their elements, i.e. technical, information and mathematical support. Let us dwell in more detail on the specifics of individual information systems.

Planned information systems. These systems are created at the administrative level of management and serve to make long-term decisions of a strategic nature. Among the tasks to be solved may be the following:

creation and optimization of supply chain links;

management of conditionally constants, i.e. low-changing data;

production planning;

general inventory management;

reserve management and other tasks.

Dispositive information systems. These systems are created at the warehouse or workshop management level and serve to ensure the smooth operation of logistics systems. The following tasks can be solved here:

detailed inventory management (storage locations);

disposal of intra-warehouse (or intra-factory) transport;

selection of goods according to orders and their completion, accounting of shipped goods and other tasks.

Executive information systems. They are created at the administrative or operational management level. Information is processed in these systems at a pace determined by the speed at which it enters the computer. These systems can solve various problems related to the control of material flows, operational management of production services, movement management, etc. The features of information systems of various types in the context of their functional subsystems are discussed above. But, as already noted. There are also differences in the supporting subsystems. Let us dwell in more detail on the characteristic features of the software of planned, discretionary and executive information systems. The creation of multi-level automated material flow management systems is associated with significant costs, mainly in the field of software development, which, on the one hand, should ensure the multifunctionality of the system, and on the other, a high degree of its integration. In this regard, when creating automated control systems in the field of logistics, the possibility of using relatively standard, inexpensive software, with its adaptation to local conditions, should be explored.

The level of standardization is highest when solving problems in planned information systems, which makes it possible to adapt standard software here with the least difficulty. In optional information systems, the ability to adapt a standard software package is below. This is caused by a number of reasons, for example:

the production process at enterprises is historical and difficult to undergo significant changes in the name of standardization;

The structure of the processed data varies significantly among different users.

In executive information systems at the operational level, as a rule, individual software is used.

2.3. Place of inventory logistics in the enterprise logistics system

According to the generally accepted logistics system, the distribution of its functional areas, from the point of view of the supremacy of the logistics subsystems of the enterprise logistics system in the overall enterprise system, the functional diagram can be determined from various positions, including functional importance, the need for management in terms of centralized management of the processes of distribution of material flows inside and outside the enterprise, etc.

Information logistics, which works with information flows as the basis for the functioning of all logistics subsystems, is followed by procurement logistics, then production process logistics and distribution logistics. These three stages are the purchase of raw materials, materials and components; production of products or provision of services; distribution of finished products or services constitute a single economic process, for the implementation of which any enterprise is created. Logistics is a view of the production of goods and services as a single and continuous process of movement of objects of labor from their original form to the final product, as well as the information associated with it. In this sense, logistics is a philosophy of the existence and development of the economy, since it contains a set of methodological principles that underlie the effective functioning of its constituent organizations. From the standpoint of logistics, the economy is (in its most general form) a set of conditionally closed chains of suppliers and consumers of products and services at various levels.

The purposes of formation and the corresponding types of reserves may be different, but regardless of this, reserves represent the second most important calculated component of the production process after the processing batch.

suppliers

External environment

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Organization

supply

material

streams

production

Information

streams

consumers

Stocks of raw materials, materials, components,

received from suppliers

Procurement

workshops Processing of raw materials and supplies

Inventory of labor items

at every workplace

semi-finished products

Processing

workshops

Production

Assembly

units

Stocks of assembly units

Stocks of labor items at each workplace

Assembly Finished assembly

Production workshops

Inventories of finished products in the organization's warehouses

Their volume, location, and dynamic dependence on the needs of subsequent stages of production largely determine the effectiveness of material flows within the organization and in the external environment. It is the reserves of raw materials, materials, components and finished products that directly link the organization with its suppliers and consumers, forming the chains of logistics systems of the economy as a whole, presented in the diagram.

Thus, inventory logistics occupies a key place in the logistics system of both an individual organization and the economy as a whole. Ensuring a unified and continuous process of supplying all stages of the production process with the necessary supplies in optimal quantities and of a given quality is the most important guarantee of the effective functioning of organizations and the regional economy.

3. Inventory logistics

3.1. Inventory category

At the firm level, inventories are among the objects that require large capital investments, and therefore represent one of the factors that determine the policy of the enterprise and affect the level of logistics services as a whole. However, many firms do not pay enough attention to it and constantly underestimate their future needs for cash reserves. As a result, firms typically find themselves having to commit more capital to inventory than expected.

Changes in the volume of inventories largely depend on the currently prevailing attitude of entrepreneurs towards them, which, of course, is determined by market conditions. When the majority of entrepreneurs are optimistic about the possibilities of economic growth, they expand their operations and increase investments in stockpiling. However, fluctuations in the levels of the latter are not caused by investment alone. Important factors here are the quality of decisions made, as well as what specific inventory management technology is used.

More than 20 years ago, Western economists tried to establish to what extent it was possible to keep the ratio of inventory levels to sales unchanged. Using the "fixed accelerator" equation (J = kD , where J is the level of inventory, units, D is demand and k is the coefficient of demand unevenness), they came to the conclusion that such a simple relationship does not correspond to real inventory management.

Using a larger volume of diverse data over a very long period and using a modified version of the specified accelerator (“flexible accelerator”), foreign researchers have suggested that firms make only partial adjustments to their inventories, bringing them closer to the desired level during each production period. Over a twelve-month period, the difference between desired and actual inventory levels could only be reduced by 50%. This change is explained mainly by the improvement of the inventory management system based on the use of computer technology.

A number of US scientists have concluded that if 75% of the fluctuations in the level of investment in inventories could be controlled, the economy of this country would not experience any of the post-war recessions during which prices, output and profits fell and unemployment grew up. The consequence of this conclusion was the demand for the government to take measures to dampen too sharp fluctuations in the level of inventories and reduce the damage that they cause.

To this end, proposals were made, including the introduction of a special tax that would be imposed on companies that allow excessive fluctuations in the level of their inventories. To date, most of the proposals have remained unrealized, since it is difficult to determine exactly what fluctuations in inventory levels are acceptable for each individual company. Moreover, some practitioners have suggested that government intervention by manipulating interest rates will not have a significant effect on firm-level inventory investment. However, the establishment of a state standard for inventory levels and the collection of fines for exceeding it in Sweden refute the excessive caution of their American colleagues and confirm the effectiveness of measures that led to a decrease in inventories and a reduction in costs for them.

Inventory has always been considered a factor that ensures the safety of the logistics supply system, its flexible operation, and is a kind of “insurance.” There are three types of inventories: raw materials (including components and fuel); goods at the manufacturing stage; finished products. Depending on their intended purpose, they are divided into the following categories:

a) technological (transitional) stocks moving from one branch of the logistics system to another;

b) current (cyclical) inventories created during the average production period, or inventories in the amount of one batch of goods;

c) reserve (insurance or “buffer”); sometimes they are called “inventories to compensate for random fluctuations in demand” (this category of inventories also includes speculative inventories created in case of expected changes in demand or supply for a particular product, for example, due to labor conflicts, price increases or deferred demand).

Thus, there are many reasons for creating inventories in firms, however, what they have in common is the desire of production entities for economic security. It should be noted that the cost of creating inventories and the uncertainty of sales conditions do not contribute to increasing the importance of an expensive backup “safety” network in the eyes of company management, since they objectively contradict increasing production efficiency.

One of the strongest incentives to create inventories is the cost of their negative level (scarcity). When there is a shortage of inventory, there are three types of potential costs, listed below in order of increasing negative impact:

1) costs due to non-fulfillment of the order (delay in sending the ordered goods) - additional costs for promoting and sending goods of the order that cannot be fulfilled using existing inventories;

2) costs due to loss of sales - in cases where a regular customer turns to some other company for this purchase (such costs are measured in terms of revenue lost due to the failure to carry out a trade transaction);

3) costs due to the loss of a customer - in cases where the lack of inventory results not only in the loss of a particular trade transaction, but also in the fact that the customer begins to constantly look for other sources of supply (such costs are measured in terms of total revenue that could have been receive from the implementation of all potential transactions between the customer and the company).

The first two types of costs are obviously among the so-called “time costs of the company as a result of adopting an alternative course.” The third type of costs is difficult to calculate, since hypothetical customers are different and so are the corresponding costs. However, it is very important for the company that the estimate of this type of cost is as close as possible to the amount of costs that could actually occur.

Keep in mind that the cost of stock outs is greater than simply the cost of lost sales or unfulfilled orders. This includes lost production time, lost working time, and possibly lost time due to costly interruptions in production during transitions between complex technological processes.

3.2. Types of stocks

Technological and transitional reserves

At any given time, a logistics supply system usually has a certain amount of inventory moving from one part of the system to another. In those cases of logistics, when moving stocks from one level to another takes a lot of time, the volumes of transition stocks will be large. With long lead times for order fulfillment (for example, with long periods of time between the production of goods and their arrival in finished form at the warehouse), the total amount of technological stocks will be relatively large. In the same way, with large time intervals between the moment the goods leave the warehouse and the moment they are received by the customer, a large amount of transitional inventory will accumulate. For example, with an average level of demand for a given product equal to 200 items per week and a delivery time to the customer equal to two weeks, the total volume of transitional inventory for this product will average 400 items.

To calculate (estimate) the average quantity of technological or transitional inventories in a given logistics system as a whole, the following formula is used:

J= ST, Formula 1

where J is the total volume of technological or transitional (in the process of transportation) inventory;

S is the average rate of sales of these inventories for a given period of time;

T - average transportation time.

Inventory in volume of one batch of goods, or cyclical stocks

A feature of most business systems is that goods are ordered in quantities that are excessive in relation to the currently needed volumes. There are a number of reasons for this, such as: a delay in receiving the ordered goods in full, which forces customers (especially intermediaries) to store certain goods in a warehouse for some time; discounts provided to customers when selling goods purchased in batches; taxation of trade transactions with a minimum size of lots, making it unprofitable to send goods to the customer in quantities less than the established size, and some others.

However, there are certain restrictions on the size of inventory. The limiting factor is the cost of storing them. Therefore, there is a need to achieve a balance between the advantages and disadvantages of ordering, on the one hand, and storing goods, on the other.

This balance is achieved by choosing the optimal volume of batches of ordered goods, or by determining the economic (optimal) order size - “economic order quantity” (EOQ), which is calculated by the formula:

EOQ = 2 AD/ vr, formula 2

where A is production costs;

D - average level of demand;

v - specific production costs;

r - storage costs.

Reserve, or “buffer”, inventories serve as a kind of “emergency” source of supply in cases where demand for a given product exceeds expectations. In practice, it is extremely rare to accurately predict the demand for goods. The same applies to the accuracy of predicting the timing of orders. Hence the need to create reserve inventories.

To a certain extent, the services a company offers are a function of its safety stock, and vice versa: a company's safety stock is a function of its services. It is clear that the company will try to minimize its safety stock levels in accordance with its stated customer service strategy. Here again a trade-off is required - this time between the costs of holding reserve inventory to accommodate unexpected fluctuations in demand and the benefits the company receives from maintaining this level of service to its customers.

Therefore, determining the exact level of safety stocks required depends on three factors, namely:

Possible fluctuations in the timing of restoration of inventory levels;

Fluctuations in demand for relevant goods during the order implementation period;

The company's customer service strategy.

Determining the exact level of safety stocks required in the face of unstable lead times and fluctuating demand for goods and materials is not an easy task. The probabilistic nature of the above fluctuations and instability means that appropriate modeling or simulation is usually necessary to find satisfactory solutions to problems associated with safety inventories.

Since in firms in various sectors of the economy the creation of inventories is determined by the specific role they play in the process of production, the differences in approaches to investment policy in this area are also understandable. To determining the priority of tasks solved during production. In firms in some sectors of the national economy, the main task is to control raw materials, in others - over finished products, and in enterprises in industries producing investment goods, most of the organizational efforts are concentrated on controlling work in progress.

Thus, companies that produce railway rolling stock produce these products according to consumer orders. No one will just create stocks of, for example, diesel engines. In the clothing industry, only minimal stocks of finished products are created, which is explained by the inconstancy of tastes and fashion. In the latter case, a significant part of the funds is invested in work in progress - semi-finished products that are prepared in order to quickly respond to changes in the needs of the product market.

The situation is exactly the opposite in companies that produce tires. Success here mainly depends on how quickly demand is met, and therefore finished products must be available. The production of custom tires is rarely carried out, since consumers prefer a certain type or brand of products. What is typical here is the repeated sale of the same product (according to the nomenclature) to the same consumer. Investment in raw material inventories and work in progress in tire industry firms is kept to a minimum level.

Many firms operating in various sectors of the economy are relatively successful in investing in inventories. At the same time, in a large number of companies there is an opinion that inventory management is the responsibility of the lower level of management - a task of a purely technical nature. At the same time, American experts who analyzed the inventory management policies of trading firms (retail and wholesale) operating in 17 different sectors of the economy came to the conclusion that if a typical unsuccessful firm did the same thing as a successful one, then it would succeeded in accelerating inventory turnover by half, i.e., with the same turnover, she could reduce inventories by 50%.

Capital turnover ratios are characterized by significant variability and differ significantly not only between successful and unsuccessful companies, but also among different types of firms. The latter is explained mainly by the specific cost structure that exists in sectors of the national economy, seasonal fluctuations in sales, competition standards adopted in a particular sector of the economy, the level of profitability, the style of enterprise management and the nature of business operations. Thus, the listed circumstances should be considered very important factors that have a serious impact on the effectiveness of the policy of any company in the field of creation and sale of inventories.

Currently, in industrialized countries with market economies, there is a very significant gap between the theory and practice of decision-making in this area, and it arose primarily for two reasons. First, in the recent past, corporate executives have placed too much emphasis on rapid sales growth at the expense of efficient inventory and production management. Secondly, many scientists and economists involved in management issues paid too much attention to the development of mathematically “pure” decision-making models that had little practical value.

These reasons had certain grounds. The national economies of most Western countries experienced an era of economic growth that characterized their post-war development. Initially, growth was achieved by vigorously covering pent-up demand that had accumulated during the war years. Subsequently, the expansion of consumer demand also supported high growth rates, which was also ensured by the formation of new domestic markets and markets in developing countries. In such an economic climate, it made sense for company management to focus their efforts on ensuring rapid growth in sales. Inventory management and production planning during this period were in the background.

In the 60s, senior management of companies had the opportunity to use the achievements of scientific and technological progress. The management of the activities of companies began to be carried out on the basis of the use of computers. In this regard, the requirements for obtaining information regarding the costs of current production activities, including the creation and storage of inventories, have increased. Inventory management and production planning began to play a more prominent role in the economic activities of companies.

In the 1970s and 1980s, even more important changes occurred in the production sector, economic growth slowed down, and this led to significant changes in the market. The buyer began to demand the maximum variety of products (or maximum freedom of choice). The number of types of products required to saturate the market is becoming larger, and accordingly, product life cycles are becoming shorter. All this led to an expansion of the range of goods and, in many cases, to an increase in production costs. Therefore, among other issues that confront the management of firms, not least important is increasing the efficiency of distribution of internal resources, i.e., improving inventory management.

3.3. Inventory management systems in companies

3.3.1. general information

In conditions of increased competition, among the measures by which it is possible to rationalize production and improve its technology, one should highlight the reduction of time for the passage of products and stocks in workshops and warehouses. The production management systems used today for this purpose always meet market requirements. Their main disadvantages include:

Too large deviations of budget planning from the real state of affairs, despite the significant costs of electronic data processing and the system as a whole;

Lack of ability to effectively influence productivity, cycle times and required inventory levels;

Insufficient freedom of action for planning structures and planning-related employees.

As foreign experience shows, in industrialized countries the effective processing time of a part is a maximum of 20% of the cycle time. This indicates that the part remains in semi-finished form for a very long time in production and leads to the creation of large inventories, and, accordingly, an increase in costs for them. Research conducted in a number of Western countries suggests that the expected profit from each percentage reduction in inventory levels can be equated to a 10% increase in turnover.

Currently, market requirements for product parameters, and, above all, for their quality, have increased significantly. This happened due to the predominance of supply over demand, the presence of excess production capacity, etc. It follows that success in competition can be achieved by those who have structured their production in the most rational way, so that its economic indicators are at the optimal level. This goal is achieved, among other measures, by:

a) reducing costs associated with the creation and storage of inventories;

b) reducing delivery time;

c) stricter adherence to delivery deadlines;

d) increasing the flexibility of production, its adaptability to market conditions;

e) improving the quality of products;

e) increasing productivity.

In recent years, there have been significant improvements in production methods, which have reduced production costs. Further cost savings, as noted above, can be achieved if the reserves inherent in the rationalization of supporting processes are realized. First of all, this relates to inventory optimization. The decisions made by the management of firms in this area ultimately relate to each individual type of product or storage item, the specific unit of which, subject to control, is called an “inventory unit” (u.s.).

The study of actually operating inventory management systems, consisting of many e.u.s., showed that there is a statistical pattern that determines the size of the need for the types of goods represented in the inventory. A typical situation is when at about 20% of e.u.z. accounts for 80% of demand in monetary terms. At the same time, inventories of consumer goods are characterized by a lower concentration of e.u.z. higher value than for inventories of industrial goods. It follows that all e.u.z. that make up the company’s reserves should not be controlled at the same level.

This conclusion is one of the most important, and it must be taken into account when managing multiple inventories, provided that they are considered in isolation from each other. This helps to identify the most important items in inventory. They are given priority when allocating time in the inventory management process in any system under consideration. However, the relative priority enjoyed by a particular product often changes, since the demand for it, as well as its cost, do not remain constant. This means that unit cost allocation is a dynamic rather than a static concept.

Today, thanks to the activation of a number of factors, including the introduction of logistics, many enterprises are consistently connected with each other, production and the inventory system become interdependent. In such a situation, production management means organizing the work of not only each link separately, but also all together as a whole. Analyzing the system of production orders, many companies began to proceed from the method of integrated regulation, which allows harmoniously connecting all the links and balancing the volumes of production and inventories. To do this, according to the management of firms, it is important to reduce their fluctuations at each stage by accurately forecasting the demand for products and implementing an ordering policy that would balance changes in demand. In addition, to achieve the desired compliance at each stage, all discrepancies must be recorded and information about them through feedback must be taken into account in the original production plan with the subsequent possibility of correction.

In order to reduce at each stage the proportionality of production volumes and inventories, currently the most widely used control method is feedback in the inventory system.

Thanks to the targeted use of organized, planned and control measures, it is possible, on the one hand, to prevent the creation of excess stocks, and on the other hand, to eliminate such a deficiency as lack of readiness for deliveries.

The logistics approach to inventory management involves abandoning the functionally oriented concept in this area, since it has the following disadvantages:

Problems arising in the creation and storage of inventories are often solved by searching for someone to blame in another structure, instead of identifying their true causes;

Any functional unit of each organizational structure develops its own inventory policy, which is not always agreed upon at a higher level;

Production is typically supported by excess inventory.

Consequently, the problem of reserves cannot be solved if the individual functions of the organized structure do not develop comprehensively. The requirement to optimize inventory has led to the need to develop a unified concept of responsibility for inventory.

With the development of logistics in companies, a restructuring of inventory management began, and their close coordination with the overall material flow of companies began to be established. In accordance with the goals of this restructuring, material flow departments were created that were independent of the warehouse sector of the enterprise's production department. Among the urgent tasks assigned to the newly created departments, one should highlight “reducing errors in warehousing to zero” and “transmitting data on the status of warehouse stocks in real time.”

The measures taken gave positive results - there was an increase in the efficiency of transportation of goods and loading and unloading operations. However, as material flows rationalized, the problem of inventory management came to the fore.

Given the potential importance of inventories, the study of the logistics system should include the problem of inventory management, which is specified in the following questions:

1. What level of inventory is necessary to have at each enterprise to provide the required level of customer service?

2. What is the trade-off between the level of customer service and the level of inventory in the logistics system?

3. How much inventory should be created at each stage of the logistics and production process?

4. Must goods be shipped directly from the factory?

5. What is the trade-off between the chosen transportation method and inventory?

6. What are the general inventory levels at this facility that are associated with a specific service level?

7. How do inventory holding costs change depending on changes in the number of warehouses?

8. How and where should safety stocks be placed?

An interesting option for solving warehousing problems is “production without warehouses,” the implementation of which is impossible without fundamental changes in the entire complex of processes that ensure production, and in itself, and requires significant financial costs. At the same time, as it turned out, it was necessary to solve several problems, among which, first of all, we highlight the task of creating a high-precision warehousing information system that allows the use of a data bank in real time.

When using this system, products are produced only in volumes that ensure sales. Raw materials and materials are purchased only in quantities necessary to meet demand. In reverse form, this system can be reduced to the formula: “only necessary products are produced, only when it is required, and only in the required volume.”

Previously, when production worked for a stable market, they could exist without taking these factors into account. In the context of a constant decrease in market stability and active monitoring of demand, expensive reserve stocks are replaced by an information system and proper management organization, which have a great effect. In this regard, supply logistics cannot abstract from what happens at the final stages. Moreover, the key factor is knowledge of the market situation and conditions of access to it.

The latest innovations in the field of production are as follows: differentiation of products at the latest possible stage of production (based on the most similar components); using the benefits of mass production not at the assembly stage, but at the stage of manufacturing components; the desire to maximize customer satisfaction at the stage of choosing a product for production. All this requires production flexibility at the shop level, achieved both through expanding the ability to change equipment and through the use of new inventory management methods - Kanban and Just-in-Time.

The essence of the Kanban system is that the initial inventory in quantity corresponds to the needs of the initial stage of the production process, and does not accumulate as before. At Toyota enterprises, the solution to this problem was to minimize the use of relatively small batches of materials and components and the time of operations. The scale of interoperational warehousing is reduced due to the synchronization of operations and leveling of the volumes of objects of labor processed at each stage. As for the storage of finished products, its volumes are reduced by reducing the duration of each operation, and, above all, the period of tool replacement.

One of the methods for reducing inventories, increasing production flexibility and the ability to withstand increasing competition has become the Just-in-Time method, which has become most widespread in the USA and Western European countries. In this context, it is necessary to highlight and characterize the fundamental idea of ​​the method, which is based on three premises (their correctness has been repeatedly confirmed empirically). In conditions of minimal inventories, continuous rationalization in the organization and management of production is necessary, because a high volume of inventories eliminates, in a certain sense, masks errors and shortcomings in this area, production bottlenecks, unsynchronized operations, unused production capacity, unreliable work of suppliers and intermediaries. Thirdly, to assess the efficiency of the production process, in addition to the level of costs and productivity of funds, one should take into account the implementation period of the application, the so-called duration of the full production cycle. Short deadlines for the implementation of applications facilitate enterprise management and contribute to increased competitiveness due to the ability to quickly and flexibly respond to changes in external conditions.

In contrast to traditional management methods, in accordance with which the central link of production planning issues production tasks to all departments and industrial units, with the Just-in-Time method, centralized planning concerns only the last link of the logistics chain, i.e., the finished goods warehouse. Other production and supply units receive orders directly from the next one located closer to the end of the supply chain.

For example, a warehouse of finished products submitted an application (which is equivalent to issuing a production task) for a certain number of products to the assembly shop, the assembly shop gives orders for the production of subassemblies by the processing shops and the cooperation department, etc.

This means that the production order is always issued to the department using (or processing) the part. Thus, the flow of material from the “source” to the “consumer” is preceded by the flow of information in the opposite direction, i.e. Just in time production is preceded by Just in time information.

Practice shows that for the effective implementation of the Just-in-Time strategy, it is necessary to change the way of thinking of the entire team involved in production and sales issues. The traditional “bigger is better” mentality must be replaced by “less is better” thinking when it comes to inventory levels, capacity utilization, production cycle expectations, or batch sizes.

The results of a detailed analysis carried out on the implementation of the Just-in-Time concept in Western European enterprises are promising. Averaged data obtained from more than 100 surveyed objects (individual projects operate in companies continuously from 2 to 5 years) are as follows:

Work-in-process inventories fell by more than 80%;

Finished goods inventories decreased by approximately 33%;

The amount of non-manufacturing inventory (materials and associated parts) ranged from 4 hours to 2 days, compared to 5-15 days before the implementation of the Just-in-Time method;

The duration of the production cycle (the period for completing tasks of the entire logistics chain) decreased by approximately 40%;

Production costs decreased by 10-20%;

Production flexibility has increased significantly.

The costs associated with the preparation and implementation of the Just-in-Time strategy are relatively small and, as a rule, pay off within a few months of the systems’ operation.

The use of the Just-in-Time strategy also provides other benefits, including non-economic ones. For example, the creation of a transparent structure of material flows in the form of intermediate links contributes to the widespread implementation of technology such as SIM (Computer Integrated Manufacturing). The use of the principles of the Just-in-Time system also has an impact a positive impact on the long-term investment policy of the enterprise, which in this case gives preference to machines and equipment associated with flexible automation of production, transport and control processes.

Over the past 15 years, many models have been developed in industrialized countries relevant to various inventory management issues. With the help of simulation, the effectiveness of the measures applied within a production or production program is proven, since the periods of passage of the product through the entire production line can be measured. Using simulation, you can also check designs for flexible production areas served by automated vehicles and estimate the costs of logistics for production. Designing warehouses using a computer makes it possible to obtain information about their optimal system, the amount of required capital investment and the costs of operating warehouses.

Firms often use mathematical models to select inventory levels by balancing the costs of preparatory activities or the costs of order fulfillment and comparing the costs of stockouts with the costs of holding inventory. Inventory holding costs include not only the cost of maintaining inventory in a warehouse, costs due to product spoilage, and the cost of obsolescence, but also the cost of capital, in other words, the rate of return that could have been obtained by using other investment opportunities with equivalent risk .

One of the options for reducing the risk when storing inventories is the use of technologies based on flexible production systems and its robotization. In this case, the advantage is the reduction of time and costs for preparatory operations. This makes it economically profitable to manufacture products in small batches, which is especially important in conditions of fierce competition and constant changes in market requirements. It is especially important to emphasize that at the same time the risk of moral disposal of stocks is significantly reduced.

3.3.2. Basic inventory management systems

Basic inventory management systems

The logistics inventory management system is designed with the goal of continuously providing the consumer with some type of material resource. The implementation of this goal is achieved by solving the following tasks:

Accounting for the current stock level in warehouses of various levels;

Determining the size of the guarantee (insurance) stock;

Order size calculation;

determining the time interval between orders.

For a situation where there are no deviations from planned indicators and inventories are consumed evenly, two main management systems have been developed in the theory of inventory management that solve the assigned tasks, meeting the goal of continuously providing the consumer with material resources. Also the systems are:

1. Inventory management system with a fixed order quantity;

2. Inventory management system with a fixed time interval between orders.

I Fixed Order Quantity System

The name itself speaks about the fundamental parameter of the system. This is the order size. It is strictly fixed and does not change under any operating conditions of the system. Determining the order size is therefore the first task that is solved when working with this inventory management system.

In domestic practice, a situation often arises when the size of the order is determined based on some particular organizational considerations. For example, ease of transportation or the ability to load warehouse space.

Meanwhile, in a system with a fixed order size, the purchase volume must be not only rational, but also optimal, i.e., the best. Since we are considering the problem of inventory management in the logistics system of a separate organization or the economy as a whole, the optimization criterion should be the minimum total costs of storing inventory and repeating orders. This criterion takes into account three factors acting on the value of these total costs:

1. Used storage area.

2. Inventory storage costs.

3. Cost of placing an order.

These factors are closely interrelated, and the very direction of their interaction is different in different cases. The desire to save as much as possible on inventory storage costs causes an increase in ordering costs. Saving costs for repeating an order leads to losses associated with maintaining excess warehouse space, and, in addition, reduces the level of customer service. When warehouses are maximally loaded, inventory storage costs increase significantly and the risk of illiquid inventory becoming more likely.

Using the criterion of minimizing the total costs of storing inventory and re-ordering does not make sense if the order execution time is too long, demand experiences significant fluctuations, and prices for ordered raw materials, materials, semi-finished products, etc. fluctuate greatly, in which case it is not advisable to save on inventory maintenance . This will most likely lead to the impossibility of continuous service to the consumer, which does not correspond to the purpose of the functioning of the logistics inventory management system. In all other situations, determining the optimal order size ensures a reduction in inventory storage costs without loss of service quality.

The optimal order size based on the criterion of minimizing the total costs of storing inventory and repeating an order is calculated using the formula (it is called Wilson’s formula):

acute respiratory infections= 2AS/i formula 3

where ORZ is the optimal order size, pcs.,

A is the cost of supplying a unit of the ordered product, rub.

S - need for the ordered product, pcs.

i is the cost of storing a unit of the ordered product,

The cost of supplying a unit of the ordered product (A) includes the following elements:

Cost of order transportation,

costs for developing delivery conditions,

cost of order execution control,

-- costs of producing catalogues,

cost of document forms.

The formula is the first version of Wilson's formula. It is focused on instant replenishment of stock in the warehouse. If the replenishment of stock in the warehouse is carried out over a certain period of time, the formula is adjusted by a coefficient that takes into account the speed of this replenishment:

ORZ= 2AS/ ik formula 4

where k is a coefficient that takes into account the speed of replenishment of stock in the warehouse.

The guarantee (safety) stock allows you to meet the demand for the duration of the expected delivery delay. In this case, by possible delivery delay we mean the maximum possible delay. The guarantee stock is replenished during subsequent deliveries through the use of the second calculated parameter of this system - the threshold stock level.

The threshold stock level determines the stock level, upon reaching which the next order is made. The threshold level is calculated in such a way that the receipt of an order stocking occurs when the current stock is reduced to the guarantee level. When calculating the threshold level, delivery delays are not taken into account.

The third main parameter of a fixed order quantity inventory management system is the desired maximum inventory. Unlike the previous two parameters, it does not directly affect the functioning of the system as a whole. This stock level is determined to track the appropriate utilization of space from the point of view of the criterion of minimizing total costs.

II System with a fixed time interval between orders

A system with a fixed time interval between orders is the second and last inventory management system, which is one of the main ones. The classification of systems into basic and other is due to the fact that the two systems under consideration underlie all sorts of other inventory management systems.

In a system with a fixed time interval between orders, as the name implies, orders are placed at strictly defined points in time, which are spaced at equal intervals from each other, for example, once a month, once a week, once every 14 days, etc. .P.

You can determine the time interval between orders taking into account the optimal order size. The optimal order size allows you to minimize the total costs of holding inventory and repeating the order, as well as achieve the best combination of interacting factors, such as the used warehouse space, inventory holding costs and ordering costs.

The time interval between orders can be calculated as follows:

I = N:S/acute respiratory infections, formula 5

where N is the number of working days per year, days,

S - need for the ordered product, pcs.

ORZ - optimal order size, pcs.

The time interval between orders obtained using the formula cannot be considered as mandatory for use. It can be adjusted based on expert assessments.

A guarantee (safety) stock allows you to meet the demand for the duration of the expected delivery delay (a possible delivery delay also means the maximum possible delay). The guarantee stock is replenished during subsequent deliveries by recalculating the order size so that its delivery increases the stock to the desired maximum level.

Since in the system under consideration the moment of the order is predetermined and does not change under any circumstances, the constantly recalculated parameter is the order size. Its calculation is based on the predicted level of consumption before the order arrives at the organization's warehouse.

Calculation of the order size in a system with a fixed time interval between orders is carried out using the formula:

RZ == MZHZ - TK + OP, formula 6

where РЗ - order size, pcs.,

MZhZ - desired maximum order, pcs.

TK - current order, pcs.

OP - expected consumption over time

As can be seen from the formula, the order size is calculated in such a way that, provided that the actual consumption during the delivery period exactly matches the expected one, the delivery replenishes the stock in the warehouse to the maximum desired level. Indeed, the difference between the maximum desired and current stock determines the order quantity required to replenish the stock to the maximum desired level at the time of calculation, and the expected consumption during the delivery period ensures this replenishment at the time of delivery.

III Comparison of major inventory management systems

We can assume an ideal, purely theoretical situation in which the order is fulfilled instantly (in other words, the delivery time is zero). Then the order can be made at the moment when the stocks of material resources in the warehouse are equal to zero. At a constant consumption rate, both considered inventory management systems (with a fixed order size and with a fixed time interval between orders) become the same, since orders will be produced at equal time intervals, and order sizes will always be equal to each other. The safety stocks of each of the two systems will be reduced to zero. A comparison of the considered inventory management systems leads to the conclusion that they have mutual disadvantages and advantages.

A fixed order quantity system requires a continuous inventory of the current stock in the warehouse. In contrast, a system with a fixed time interval between orders requires only periodic control of the stock quantity. The need for constant/even inventory in a system with a fixed order quantity can be considered as its main disadvantage. On the contrary, the lack of constant control over the current stock in a system with a fixed time interval between orders is its main advantage over the first system.

A consequence of the advantage of a system with a fixed time interval between orders is that in a system with a fixed order size the maximum desired inventory is always smaller than in the first system. This leads to savings on inventory holding costs by reducing the space occupied by inventory, which in turn leaves the advantage of a system with a fixed order quantity over a system with a fixed time interval between orders.

3.3.3. Other inventory management systems

The basic inventory management systems discussed above are based on fixing one of two possible parameters - order size or time interval between orders. In the absence of deviations from planned indicators and uniform consumption of stocks for which the main systems have been developed, this approach is quite sufficient.

However, in practice other, more complex situations are more common. In particular, with significant fluctuations in demand, the main inventory management systems are not able to ensure uninterrupted supply to the consumer without significantly overestimating the volume of inventory. If there are systematic failures in supply and consumption, basic inventory management systems become ineffective. For such cases, other inventory management systems are designed, which are called others.

Each of the main systems has a specific operating procedure. Thus, in a system with a fixed order quantity, an order is made when a threshold stock level is reached, the value of which is determined taking into account time and possible delivery delays. In a system with a fixed time interval between orders, the order size is determined based on the available inventory volumes and the expected consumption during the delivery time.

Various combinations of links in the main inventory management systems, as well as the addition of fundamentally new ideas to the system operation algorithm, lead to the possibility of creating, in fact, a huge number of inventory management systems that meet a wide variety of requirements. The most common other systems. This:

1. A system with a set frequency of replenishing stocks to a constant level,

2. Minimum-maximum system

I A system with a set frequency of replenishment of stocks until established level

In this system, as in a system with a fixed time interval between orders, the input parameter is the time period between orders. Unlike the main system, it is designed to operate with significant fluctuations in consumption. To prevent inventory levels from being overstated or stocked out, orders are placed not only at set times, but also when inventory reaches a threshold level. Thus, the system under consideration includes a system element with a fixed time interval between orders (established order frequency) and a system element with a fixed order size (tracking threshold inventory levels).

The guarantee (safety) stock allows you to provide the consumer in the event of an expected delay in delivery. By possible delivery delay, as noted above, we mean the maximum possible delay. The guarantee stock is replenished during subsequent deliveries by recalculating the order size so that its delivery increases the stock to the maximum desired level. The safety stock does not directly affect the functioning of the system as a whole.

From an inventory management system with a fixed order quantity, the system in question borrowed the threshold inventory level parameter. The threshold stock level determines the stock level upon reaching which the next order is made. The value of the threshold level is calculated based on the value of the expected daily consumption in such a way that the order is received at the moment the current stock decreases to the guarantee level. Thus, a distinctive feature of the system is that orders are divided into two categories. Planned orders are produced at specified time intervals. Additional orders are possible if stock levels reach the threshold level. Obviously, the need for additional orders can only appear if consumption rates deviate from the planned ones.

The maximum desired supply is that constant level to which replenishment is considered appropriate. This level of inventory is indirectly (through the time interval between orders) related to the most rational loading of warehouse space, taking into account possible supply failures and the need for uninterrupted supply of consumption.

A constantly calculated parameter of the inventory management system with a set frequency of replenishing stocks to a constant level is the order size. As in a system with a fixed time interval between orders, its calculation is based on the predicted level of consumption before the order arrives at the organization's warehouse.

The calculation of the order size in the system under consideration is carried out either according to formula 6 (at fixed moments of orders) or according to the formula (at the moment the threshold level is reached):

RZ = MZHZ - PU + OP, formula 7

where РЗ - order size, pcs.,

MZhZ - maximum desired order, pcs.,

PU - threshold stock level, pcs.,

OP - expected consumption until delivery, pcs.

As can be seen from the formula, the order size is calculated in such a way that, provided that actual consumption (up to the time of delivery) exactly matches the forecast, the supply replenishes the stock in the warehouse to the maximum desired level.

II Minimum-maximum system

This system, like a system with an established frequency of replenishment of inventories to a constant level, contains elements of basic inventory management systems. Like the fixed time interval system, this one uses a constant time interval between orders. The “Minimum-Maximum” system is focused on a situation where the costs of inventory accounting and ordering costs are so significant that they become commensurate with losses from inventory shortages. Therefore, in the system under consideration, orders are not made at every given time interval, but only on condition that the stocks in the warehouse at that moment are equal to or less than the established minimum level. In the case of issue, the size is calculated so that the delivery replenishes the inventory to the maximum desired level. Thus, this system works with only two levels of inventory - minimum and maximum, which is where it gets its name.

The guarantee (safety) stock allows you to provide the consumer in the event of an expected delay in delivery. Like a system that regularly replenishes inventory to a constant level, safety stock is used to calculate a threshold inventory level.

The threshold stock level in the Minimum-Maximum system acts as a “minimum” level. If at a set point in time this level is passed, i.e. If the available stock is equal to the threshold level or does not reach it, then the order is placed. Otherwise, the order will not be issued and the threshold level will be tracked and the order will be issued only after a specified time interval.

The maximum desired stock in the “Minimum-Maximum” system serves as the “maximum” level. Its size is taken into account when determining the order size. It is indirectly (through the time interval between orders) related to the most rational loading of warehouse space, taking into account possible supply failures and the need for uninterrupted supply of consumption.

A constantly calculated parameter of the “Minimum-Maximum” system is the order size. As in previous inventory management systems, its calculation is based on the predicted level of consumption before the order arrives at the organization's warehouse. The order size is calculated using formula 7. As is known, a special department of the enterprise’s marketing system is involved in collecting and analyzing information about the state of the market, as well as about the state of demand for goods produced by the enterprise, fluctuations and dependencies of demand. Based on the results of the research, information flows are exchanged between the marketing and sales subsystem, on the one hand, and the logistics subsystem, the warehousing/inventory logistics department.

4. Methodological basis for designing an effective logistics inventory management system

Basic inventory management systems - with order sizes and with a fixed time interval between orders, as well as other inventory management systems - with an established frequency of replenishment of stocks to a constant level and the "Minimum-Maximum" system are developed for conditions when there are no deviations from the planned delivery parameters and consumption. These parameters are:

Order size

Time interval between orders,

Delivery time,

Possible delivery delay,

Expected daily consumption

Forecasted consumption until delivery. Continuously meeting the need for any type of material resource is associated with certain difficulties. First of all, this is the possibility of various deviations in the values ​​of the indicators listed above, both on the part of the consumer of the stock and on the part of the order executor. In addition, it is quite possible that performers make mistakes that lead to disruption of the normal functioning of the inventory management system.

The following deviations of planned and actual indicators are practically possible:

Change in consumption intensity in one direction or another,

Delivery of unplanned order quantity,

Errors in accounting for actual inventory, leading to incorrect determination of the order size.

Quite often, there are various combinations of disturbing influences that deviate the inventory management system from normal functioning.

In the inventory management systems discussed earlier, despite their orientation toward stable operating conditions, the possibility of smoothing out supply and consumption disruptions is provided.

Thus, a system with a fixed order quantity takes into account one of the eight disturbance effects, namely delivery delay. This impact is removed by introducing the guarantee (safety) stock parameter into the system. It allows you to meet demand for the duration of the expected delivery delay. If the possible delivery delay represents the maximum possible delay, then the mechanism of the system will protect the consumer from shortages in the event of a single supply failure. The second calculated parameter of the system, the threshold level, ensures that the system is maintained in a deficit-free state. The period of time through which the guarantee stock is replenished to the calculated volume depends on the specific values ​​of the initial and actual parameters of the system.

System with a fixed time interval between orders also takes into account the disturbance effect of delivery delay. As in a system with a fixed order size, this impact is removed by the guarantee (safety) stock parameter. Replenishment of the guarantee stock to the estimated volume is carried out during subsequent deliveries through recalculation of the order size in such a way that its delivery increases the stock to the desired maximum level. If the forecast of consumption until the moment of future delivery was accurate, the system mechanism with a fixed time interval between orders will protect the consumer from shortages of material resources in the event of supply failures.

A system with an established frequency of replenishing inventories to a constant level, in contrast to basic inventory management systems, takes into account the possibility of both delays in delivery and changes in consumption rates from planned. Increasing the system's ability to withstand unplanned disturbances is associated with combining the ideas of using a threshold level and a fixed interval between orders. Monitoring the threshold level increases the system's sensitivity to possible fluctuations in consumption intensity.

The “Minimum-Maximum” system is focused on a situation where the costs of accounting for inventory in a warehouse and the costs of placing an order are so significant that they become commensurate with losses from inventory shortages. This is the only system previously discussed that allows stock shortages for economic reasons. However, the Minimum-Maximum system also takes into account the possibility of delivery delays through the safety stock parameter.

Thus, the considered basic and other inventory management systems are applicable only to a very limited range of operating conditions and interaction between suppliers and consumers. Increasing the efficiency of using an inventory management system in an organization's logistics system leads to the need to develop original inventory management systems. In the theory of inventory management, there are a sufficient number of special ways to conduct such work.

5. Conclusion

As we have already indicated above, information flows and material flows, as well as their role in the logistics management system of an enterprise, are interconnected and interdependent. Information flows provide sufficient knowledge about the need to create inventories, their volume and quality, including in connection with planning the production of a batch of products for the short term and competition in the market. Thus, we see that in terms of organizing inventory logistics processes, information flows play a significant role.

This means that information flows need to be well organized, thought out and calculated, thus one of the most important tasks of information logistics is to ensure the effective generation and use of information.

The implementation of the planned radical changes in the political, social and spiritual life of society is inextricably linked with the management system, production relations, and qualitative changes in the content of working conditions and living conditions of workers. At the present stage, information technology is one of the most significant areas of scientific and technological progress, directly affecting the dynamism of the development of society.

Logistics in Russia as a science began to develop relatively recently (about 2 years ago), but now we can talk about its importance in the enterprise. The newly formed logistics departments combine existing analytical, statistical services, customs departments, etc. But the benefit to the enterprise brought by such a department is much higher than the scattered work of the above listed services. Although the capabilities of logistics are much broader than planning, analysis, etc. In fact, the logistics department should be a connecting link in the work of all services of the enterprise, so to speak, the coordinating center of the company.

There is already a demand for specialists of this profile in the labor market. Perhaps in the near future the logistics profession will be one of the ten most prestigious and in-demand specialties.

So, let us note the fact that inventory logistics, regardless of the inventory management model, the main role is played, first of all, by the employees of the enterprise, their qualifications and interest in uniformly increasing the profit of the enterprise. Inventory logistics is

a significant direction in the activities of the enterprise.

The management of the enterprise itself selects personnel, selects models and methods of functioning of the logistics system in general and inventory logistics in particular.

The main thing in this matter is the staff, that is, the performers, as well as senior managers. It depends on the managers how well the work will be carried out on inventory planning, direction of warehouse processes and personnel management of this subsystem of the enterprise’s logistics system.

6. List of used literature:

“Logistics”: Ed. B.A. Anikina - M.: INFRA-M, 2002.

Nerush Yu.M. “Logistics” - M.: UNITY, 2000.

Kozyrev V.K., Tikhonin V.I. Optimal loading of warehouses and vehicles: Guidelines for course design - O., 1998.

Gadzhinsky A.M. Fundamentals of logistics: Textbook.

- M.: Marketing, 1996 Management reserves Deterministic models

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   at the enterprise using the example of the OJSC Khlebprom enterprise

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INVENTORY MANAGEMENT MODELS	Rubric (thematic category)

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CLASSIFICATION OF MATERIAL RESERVES Stock

– form of existence of a material flow. If the entire logistics chain along which the material flow moves worked like one mechanical conveyor, waiting time could be reduced to zero and inventories could be eliminated. However, this should not be expected in real life. The material flow along the path from the source to the final consumer can accumulate in the form of a reserve at any site. For this reason, stocks of raw materials, materials, finished products, etc. are distinguished. All stocks can be divided into the following groups:

production, commodity. Each, in turn, is divided into groups according to the function it performs: current, insurance, seasonal. The purpose of creating inventories

– ensuring uninterrupted production process.– stocks of finished products at manufacturing enterprises, stocks of wholesale and retail trade enterprises, as well as stocks in transit. Current stocks- the main part of industrial reserves. Such reserves ensure continuity of production and trade processes between successive deliveries. Safety stocks designed to provide material and commodity resources in case of unforeseen circumstances: deviation in the frequency and size of deliveries; unexpected increase in demand. Seasonal stocks are formed due to the seasonal nature of production (agricultural products). Maximum Desired Stock- ϶ᴛᴏ stock level that is economically feasible in a given system. The threshold stock level is used to determine when to order the next batches. The current stock at any time can coincide with the maximum stock, trading level and guarantee (insurance) stock.

The logistics inventory management system is designed to ensure continuous production. The implementation of this goal is achieved by solving the following tasks: accounting for the current level of stock in warehouses; determining the size of the guarantee (insurance) stock; order size calculation; determining the time interval between orders.

Exist two main models of inventory management system: model with a fixed order quantity (Q-model); model with a fixed period between orders (P-model). Fixed order quantity management systems. When managing according to the Q-model, the next purchase order is placed at the moment when the stock of material decreases to a threshold level. This can happen at any time and depends on the volume of consumption. The use of this system involves constant monitoring of the remaining inventory. The Q model is recommended for inventory management of high-value resources because it provides the lowest average order size. At the same time, this model is characterized by high labor intensity of maintenance; therefore, for less expensive objects, a system with a fixed time between orders is used. Inventory management system with a fixed period of time between orders. When managing inventory by R-model, the next order is placed after a predetermined period. At R-model, the calculation of the remaining stock is made only after the control period of time has elapsed.

The P-model has a larger reserve since the resources must be sufficient until the next delivery at a fixed interval.

30. RULE 80–20. ABC ANALYSIS. XYZ ANALYSIS

Rule 80–20 used for structuring inventories, i.e., for identifying from the entire range of inventories those that should be optimized first: 20% of inventories account for approximately 80% of their value or sales dynamics, and 80% of inventories account for 20% of cost or sales volume. The difference between LAN analysis and the 80–20 rule is that to carry it out, the entire inventory range is divided into three groups, rather than two.

In most cases, the product range is so wide that modeling and analysis of each item is impossible. To simplify the solution of the problem, carry out ABC-analysis, on the basis of which all resources are divided into the following groups: L– high cost volume; IN– moderate cost volume; WITH– low cost volume. To classify inventories by importance (LAN analysis), the share of the cost of each item in the total cost of inventories is determined, and then they are arranged in descending order. Next in group A include approximately the top 20% of the ordered list items, whose total value represents 75–80% of the total inventory value. IN group IN include approximately 30% of items, the share of value of which is up to 70%. IN group WITH include the remaining positions, approximately 50%. The purpose of these procedures is essentially to separate the significant from the non-essential items.

This method gives the greatest effect in combination with method XYZ which allows you to classify the same range of stocks, but based on the dynamics of their consumption. The grouping of resources in XVZ analysis is carried out in increasing order of the coefficient of variation of demand for a product over a certain period of time, which is calculated for each assortment item:

Where Xi– demand value for the position being evaluated; X- average quarterly demand; P– number of quarters.

TO categories X include resources with a demand variation coefficient of less than 10%. Οʜᴎ are predictable, characterized by a stable amount of consumption. Category Y - ϶ᴛᴏ resources, the coefficient of variation for which changes dynamically from 10 to 25%. Category Resources Z are consumed irregularly, the accuracy of their prediction is low, and the coefficient of variation is more than 25%.

Combining the results of application ABC– And XYZ- Using analysis methods, we obtain 9 groups of reserves, for each of which the company must develop its own management options. AH groups, AY And AZ require the most attention. It is worth saying that they use a model with a fixed order size, calculate the optimal order size and use just-in-time delivery technology. For CX group resources, СY And СZ simplified planning methods are used, and their management functions are, as a rule, transferred to lower levels of the production chain.

INVENTORY MANAGEMENT MODELS - concept and types. Classification and features of the category "STOCK MANAGEMENT MODELS" 2017, 2018.

An inventory management system is a set of measures to create and replenish inventories, organize continuous monitoring and operational supply planning.

The main mechanism of the inventory management system, which must be implemented in the work of all elements, is the implementation of the feedback principle. The essence of this principle is that if the management of the system exerts a control influence on its working element, then there must be a “feedback” in the system, which provides data on the new state of the entire system and evaluates the effectiveness of its functioning. The system will be controllable if, after influencing it, it is possible to determine its new state, evaluate it and, taking into account the new data obtained about the system, take the next corrective action on it.

At the first level of the system, modules of the warehouse program and databases are located, which accumulate information about the movement of goods and work with customers on the shipment of goods.

The second level of the system consists of various inventory management models that use the necessary mathematical apparatus to assess the current state of inventories and develop recommendations for their effective management.

At the third level there is a financial management model and rules that allow you to control the financial condition of inventories. Here, the economic efficiency of the adopted rules for the formation of inventories is assessed, financial sources for their acquisition and the overall financial strategy for inventory management are determined.

Thus, the basis of the inventory management system is the technology for analyzing the state of inventories and the external environment, as well as the rules for making decisions on the formation of inventories. The rules themselves can be implemented in the form of specialized software modules and instructions for personnel.

As part of many theoretical studies and extensive practical experience in solving the problem of inventory management, a number of companies use one of the following systems, which have their own advantages and disadvantages.

In the process of inventory regulation, various quantitative levels of inventory are distinguished:

The maximum reserve is equal to the sum of the guaranteed, preparatory and maximum current reserves. Its size is set to control excess resources,

Average, or carry-over stock, equal to the sum of guaranteed, preparatory and half of current stocks. The value of this indicator corresponds to the standard stock size;

Minimum reserve equal to the sum of guaranteed and preparatory. A decrease in inventories to this level is a signal for their emergency replenishment.

In the inventory management process, it is important to establish the moment, or point of order, and its required size.

The order point is a set maximum stock level, upon reaching which an order is submitted for the supply of the next batch of material assets.

Order quantity is the quantity of materials that must be ordered to replenish stock. If the minimum stock is reached at the time a new batch is received, it reaches the maximum level.

You can adjust the order size by changing the volume of batches, the interval between deliveries, or changing the volume and delivery interval. Depending on this, the following systems are used in inventory management practice:

1. System for monitoring the status of inventories with a fixed order frequency. According to this system, inventory control is carried out at regular intervals (week, decade, month) through an inventory of balances. For example, every Tuesday the manager of a company reviews the stock of goods and places an order for the supply of a new batch of goods. Thus, the time interval between orders remains constant, and the order size varies depending on the intensity of consumption, i.e. is a variable quantity.

T - fixed time interval between deliveries of goods

The size of the ordered batch of goods is determined by the difference between the maximum inventory provided by the norm and the actual inventory. Since fulfilling an order requires a certain period of time, the size of the ordered batch increases by the amount of expected consumption for this period (safety stock). The size of the ordered batch (P) is determined by the following formula:

P = z max - z fact + z page,

where Z max is the maximum reserve provided for by the norm; 3 fact - actual stock at the time of inspection: 3 page - safety stock.

The intensity of demand in this model is the magnitude of the variable. And since the order is carried out at regular intervals, the size of the ordered batch will be different in different periods. Consequently, this system can be used when it is possible to order batches of different sizes. For example, in the case of container or wagon delivery of goods, this system is unacceptable. In addition, the system is not used if delivery or placing an order is expensive. For example, if demand over the past period was insignificant, then the order will also be insignificant, which is permissible only if the costs associated with fulfilling the order are insignificant. Another feature of the system is that it allows for shortages. If demand increases sharply, the product stock will run out before the order deadline. This means that the system is applicable when possible losses from shortages for the enterprise are imperceptible.

Thus, an inventory control system with a fixed order frequency is used in the following cases:

Delivery conditions allow us to receive orders in batches of various sizes;

Ordering and delivery costs are relatively low;

Losses from a possible shortage are insignificant.

The advantage of the considered system is its simplicity, since regulation is carried out once during the entire interval between deliveries. Disadvantages of the system include the risk of exhaustion of stocks due to their unexpected intensive consumption before the next ordering moment.

2. Inventory control system with a fixed order size. In this system, the size of the replenishment order is a constant value. The time intervals at which the order is placed may be different in this case. The quantity of ordered products is determined by agreement between the supplier and the buyer. It is definite and fixed, and the order time is taken as a variable. An order for the supply of the next batch is given when the stock in the warehouse is reduced to the established threshold level - the order point. The intervals between deliveries of successive batches to the warehouse depend on the intensity of consumption (consumption) of material resources. After placing the next order, the stock continues to decrease, since the order is not fulfilled immediately, but after a certain period of time (T). The inventory level corresponding to the order point is equal to the expected demand during the delivery backlog time plus the safety stock:

where Z is the stock of the order point; P - average daily consumption of material; T - order fulfillment period; 3 pages - safety stock.

The amount of stock at the order point is chosen such that in a normal working situation during time T the stock does not fall below the insurance value. If demand unexpectedly increases or the delivery date is missed, the safety stock will begin to work. In this case, the commercial service of the enterprise must take measures to ensure additional supply. As you can see, this control system provides for protecting the enterprise from the formation of shortages.

In this case, it is conventionally assumed that the time interval between submitting a purchase order and the arrival of the batch at the warehouse (T) is constant

In practice, a stock control system with a fixed order quantity is used mainly in the following cases:

Large losses due to lack of stock;

High costs of storing inventory;

High cost of the ordered goods;

High degree of demand uncertainty;

Availability of price discount depending on the quantity ordered.

The advantage of this system is that the receipt of material in identical batches leads to a reduction in the costs of delivery and inventory maintenance. The disadvantage of the system is the need for constant labor-intensive control over the availability of inventories and, as a result, an increase in the costs associated with their regulation.

3. A system for managing the stock status of a material resource with a maximum (or production) stock level and random demand. The movement of inventories (receipt, consumption) in the control system under consideration is carried out at random times.

A system with a maximum inventory level and random demand must have the ability to adjust the size of the requirement for resource consumption, since otherwise situations with absolute shortages may be created. In this regard, it is necessary to consider the various situations that characterize the inventory management system with its maximum level and random demand.

The system is, in principle, organized by one parameter - the maximum stock level. The threshold level is only a guideline when determining when to place an order. Since the demand in the system is by condition a random value, therefore, at any point in time, resource consumption can be different in value, including equal to the entire remainder of the resource, which forms an absolute shortage of the resource until the next supply.

Such a system is organized in those fairly frequent cases when the demand for a resource in production or trade is highly uneven, and this unevenness is a function of the order size, order time and the number of consumers.

High demand for a resource often ends in a sharp decline. This circumstance forces us to form a resource stock based on two possible states: 1) production stock and 2) marginal stock, i.e. ensure resource consumption in the intervals between deliveries (production stock) or for the duration of one turnover of working capital (marginal stock). If the demand for a resource is high, then you should focus on the maximum supply; if the demand for a resource falls, then its production version can be a guideline for the required stock.

4. The “Minimum-Maximum” inventory management system is fundamentally different from other systems due to the fact that it is focused on a situation with significant costs for maintaining inventories and replenishing them. In this system, the costs associated with inventory management can be commensurate with losses from inventory shortages, and orders are fulfilled provided that the inventory in the warehouse at a certain point in time is equal to or less than the established minimum level. The order size is calculated so that the delivery replenishes the inventory to the maximum level. Thus, inventory management in the system under consideration is carried out at two levels: minimum and maximum, which determined its name.

If at the time of placing an order there is less stock remaining than the specified minimum level, then a situation with a resource shortage may arise. This circumstance must be taken into account at the time of writing off part of the resource as an expense based on a requirement or a limit card. In other words, at the time the resource is written off, the remaining stock must be no less than what is provided for by the program.

Necessary inventory management parameters in the “Minimum-Maximum” system:

The need for material resources and the average daily consumption were determined;

Established: minimum and maximum reserves; order fulfillment time and possible delivery delays;

Guaranteed stock is represented by the sum of preparatory and safety stocks;

The minimum stock level is the difference between the maximum and guaranteed stocks.

The “Minimum-Maximum” system is preferred when it is necessary to quickly respond to changes in sales.

When designing a logistics inventory management system, a number of factors must be taken into account:

1) production capacity;

2) the volume of products produced over a certain period of time (day, week, month);

3) current inventory level;

4) the required size of the guarantee (insurance) stock;

5) frequency of delivery.

The main inventory management systems are a system with a fixed order size, a system with a fixed time interval between orders, MRP-1, MRP-2, etc.

Fixed Order Quantity System is an inventory management model in which the main determining factor is determining the optimal order size, the size of which does not subsequently change. The optimal order size (ORS) is determined taking into account the minimization of the total costs of storing and repeating the order. It is calculated by the formula Wilson:

acute respiratory infections— optimal order size, pcs.;

A— costs of supplying a unit of the ordered product, rub.;

S

x — costs of storing a unit of the ordered product, rub./piece.

System with a fixed time interval between orders is an inventory management model in which the main determining factor is determining the time interval between orders, taking into account the optimal order size. The optimal order size allows you to minimize the total costs of storing inventory and repeating the order.

The time interval between orders is determined as follows:

D— number of working days per year, days;

S— need for the ordered product, pcs.;

acute respiratory infections— optimal order size, pcs.

The materials requirements planning system (MRP-1 and MRP-2) is an inventory management model in which production, and therefore inventory, is planned based on the demand for final products. These systems belong to push systems for promoting material flows. The pushing system is a system for supplying materials (components) from the previous technological operation to the next one, regardless of needs. In such a system, orders are generated in accordance with the sales volume forecast. The MRP-1 and MRP-2 systems use a large number of different computer programs that provide coordination and operational regulation of supply, production and sales functions throughout the company in real time. Determining the need for materials involves solving a number of problems in forecasting demand, inventory management, procurement management, etc.

In the MRP-1 system processing and adjustment of information on the arrival, movement and consumption of materials (raw materials, components), inventory accounting at the place of their storage, selection of strategies for replenishment and control of inventory levels for each item in the nomenclature of raw materials and supplies, control of the speed of inventory turnover, etc. . To solve procurement management problems, an orders file is used, into which information about orders and their implementation is entered.

MRP-2 system is an improved material requirements planning system and differs from the MRP-1 system primarily in the range of functions performed. It combines production, financial planning and logistics operations.

Inventory management is a solution to problems related to accounting, systematization, analysis and optimization of inventory levels. Inventory management is based on the study of the patterns of formation and consumption of inventories. A stock consists of usable but unused resources. The stock problem arises when the quantity of resources can be adjusted. The purpose of solving the problem— minimization of actual or expected costs.

One of the main tasks in inventory management is to achieve optimal proportionality between production volumes and inventories.

Controlled Variables in the Inventory Problem

1. Incoming volume of resources, those. how much needs to be purchased, released, etc.

2. Frequency or timing of resource receipts, those. frequency and time points. These variables can be adjusted separately or together.

3. Product readiness level, stored as reserves. The higher the degree of readiness of stocked products, the smaller the delay in meeting demand, but the higher the cost of creating a stock.

Uncontrollable variables are divided into cost and other

1 . Inventory holding costs increase in direct proportion to the increase in stock volume and storage time. Cost components:

1) costs of warehouse operations (labor, cost of loading and unloading mechanisms, etc.);

2) storage cost, incl. premises fee;

3) insurance premiums and taxes;

4) depreciation charges, losses from product spoilage, losses from obsolescence (fashion goods, food products).

2. Deficiency losses and penalties.

3. Costs due to changes in pace production. For example, increasing the pace means staff training, decreasing the pace means dismissal.

4. Purchase price or direct costs production. The cost of purchases depends on wholesale.

5. Demand- the volume of production required during a certain period of time. For example, should a new batch of products be launched into production?

6. Order completion time— the time interval between the moment of placing an order and the moment of replenishment of stock.

7. Volume of products supplied.

Inventory management problems arise everywhere, incl. and when accounting for labor reserves (for example, in security agencies, the question arises of how many employees are needed. When training a smaller number, it may be necessary to pay overtime.

At the firm level, inventories are among the objects that require large capital investments, because this is a factor that determines the policy of the enterprise and affects the level of logistics services.

Since demand is a random quantity, graphically it is a stepped line. But for an analytical description it is replaced by a straight line or a curve.

When replenishing supplies, two cases are possible.

1. Time interval from the conclusion of the contract for delivery before receipt is 0.

2. Product replenishment is delayed.

IN In the first case, two control methods are distinguished.

1. Periodic S - var, T - const.

The disadvantage of such management is the possibility of running out of stock, which entails more expensive management.

2. Relaxation— quantity of production S — const, T — var. T and S are not equal, but depend on the law of change in stock.

There is no risk, management is cheaper. In the second case, the value corresponding to the moment of receipt is known and constant, the moment itself is not fixed.

Logistics Concepts in Inventory Management

Inventories as an economic category play an important role in the areas of production and circulation of products. Inventory management is an essential condition for the successful functioning of any company. Currently, there are a large number of inventory management systems, each of which is associated with logistics costs. The following optimization criteria can be used: minimum logistics costs associated with inventory management; minimum order fulfillment time; maximum reliability of delivery, etc.

The most widely used logistics concept in the world is the Just-in-time (JIT) concept. The original slogan of this concept was the potential elimination of inventories of materials, components and semi-finished products in the production process of assembling cars and their main components.

The initial statement was that if the production schedule is given, then it is possible to organize the movement of material flows in such a way that all materials, components and semi-finished products will arrive in the required quantity, to the right place and exactly on time for the production or assembly of finished products. With this arrangement, insurance reserves, which froze the company's funds, were not needed.

The Just-in-Time concept eliminates the requirement for a minimum inventory - resources must arrive as production needs arise.

The Just-in-Time concept is a modern concept for building a logistics system in production, supply and distribution, based on synchronizing the processes of delivering material resources and finished products in the required quantities by the time the parts of the logistics system need them, in order to minimize costs associated with creating inventories.

The operation of a logistics system built on the principles of the Just-in-Time concept can be represented as a two-bin inventory management system. One bin is used to meet production or distribution demand, and the other is replenished as the first is used up. Material flow management in this case is carried out by “pulling” the order (Fig.).

Rice. Pull material flow management system. MP - material resources, NP - work in progress, GP - finished goods

The Just-in-Time concept is characterized by the following main features:

1) minimal (zero) inventories of material resources, work in progress, finished products;

2) short production (logistics) cycles;

3) small volumes of production of finished products and replenishment of orders (supplies);

4) relationships for the purchase of material resources with a small number of reliable suppliers and carriers;

5) effective information support,

6) high quality of finished products and logistics services.

The Just-in-Time concept allows you to: minimize inventory levels; improve the quality of finished products and services; change the corporate style of management.

Information support for the operational management of material flows based on the Just-in-Time principle is implemented by the KANBAN micrologistics system, developed and implemented by Japanese automotive companies. The KANBAN micrologistics system is a system for organizing a continuous production flow, capable of rapid restructuring and requiring virtually no safety stocks.

The means of transmitting information in the system is a special “kanban” card in a plastic envelope. Two types of cards are common: selection and production order.

The selection card indicates the number of parts (components, semi-finished products) that must be taken at the previous processing (assembly) site; the order card indicates the number of parts that must be manufactured (assembled) at the previous production site. These cards circulate both within the enterprise and in the external environment - between the corporation and companies cooperating with it, as well as at branch enterprises.

An analysis of global experience in using the KANBAN micrologistics system shows that it makes it possible to reduce production inventories by 50%, inventory by 8%, with a significant acceleration of working capital turnover and an increase in the quality of finished products.

The concept of “requirements/resource planning” is often contrasted with the “just-in-time” concept, meaning that push-type logistics systems are based on it.

A push (pull) system is a production organization system in which parts, components and semi-finished products are moved from the previous technological operation to the next one in accordance with a pre-formed rigid production schedule (Fig.).

Rice. 12. Push-out material flow management system. MP - material resources, IP - work in progress, GP - finished goods.

Material resources and semi-finished products are “pushed” from one link of the production logistics system to another. A common disadvantage of the push system is insufficient tracking of demand with the mandatory creation of safety stocks. As a result of storing inventories, the turnover of the enterprise's working capital slows down, which increases the cost of production of finished products.

Proponents of this concept note greater stability in the face of sharp fluctuations in demand and unreliability of resource suppliers compared to the just-in-time concept.

The basic micrologistics systems of this concept are the production resource planning (MRP) system and the product distribution planning (DRP) system.

The usual practice of using MRP systems in business is associated with planning and monitoring procedures for ordering and supplying (purchasing) material resources, usually of a wide range for industrial enterprises manufacturing engineering products.

The objectives of MRP implementation are:

Increasing the efficiency and quality of planning resource requirements;

Planning the production process, delivery schedule, procurement;

Reducing the level of inventories of material resources, work in progress and finished products;

Improving inventory control procedures;

Reduce costs associated with these logistics functions.

The implementation of logistics goals in the MRP system can be expressed in the form of a diagram (Fig.).

Rice. Implementation of logistics goals in the MRP system

MRP systems are mainly effective in the following cases:

When the demand for initial material resources is highly dependent on consumer demand for final products;

When a company has sufficiently long production cycles in conditions of uncertain demand.

The DRP system is the extension of the logistics of building MRP systems to the distribution channels of finished products. They are determined by the production schedule, which is regulated and controlled by the manufacturer of the finished product.

The operation of DRP systems is based on consumer demand, which is not controlled by the manufacturer. Therefore, MRP systems are generally characterized by greater stability compared to DRP systems.

The logistics tool in DRP systems is a schedule (schedule), which coordinates the entire process of supply and replenishment of finished products in the distribution network. This schedule is generated for each allocated storage unit and each link in the logistics system (manufacturer’s own warehouses or warehouses of wholesale resellers).

The DRP system allows you to solve the following problems:

Planning and coordination of logistics and marketing functions;

Forecasting market conditions;

Planning the size and location of supplies and inventory levels at the central and regional warehouses of the manufacturer;

Optimization of logistics costs for storing and managing inventories of finished products;

Reducing the delivery time of finished products;

Transportation planning, etc.

The main tasks solved in inventory management are what, when and in what quantities to order in order to maintain optimal inventory levels.

There are two main models used:

Fixed order quantity model;

Model with a fixed order frequency.

Let us consider in detail the first system, which is simple and somewhat classical. In this system, the order size is constant, and a repeat order is submitted when the available orders decrease to a certain critical level - the order point.

Determining the optimal value of the order volume is finding the best combination of storage cost and order fulfillment cost, which are in inverse proportion. With small volumes of orders, warehouse costs for their maintenance are reduced, but the costs of renewing the order and its delivery increase (orders have to be placed more often). With an increase in the size of the purchase lot, purchasing costs are reduced, it is possible to obtain wholesale discounts, but the cost of warehousing increases.

Total annual inventory costs are the annual holding cost and the annual inventory ordering cost. The optimal value of the order quantity is called “economic order quantity models” (EOQ) and is defined as the order quantity at the minimum value of the total annual inventory costs. In practical activities, it is important for an enterprise, as already mentioned, not only to determine the optimal inventory level, but also to plan a schedule for maintaining the target level throughout the entire budget period (production logistics tasks).

Applied models of inventory management are built on the same methodological principles of comparing “benefits - costs”, but are expanded from the point of view of planning the items “Incoming” and “Expensing” of inventories over time (within the framework of a short-term, for example, quarterly budget). The most well-known applied inventory management models used in the West are:

The EOQ model (economic order quantity, that is, “calculation of the optimal value of one purchase of replenishment of stocks”) - for stocks of material resources;

The EPR model (economic production run, that is, “calculation of the optimal size of one production batch”) - for finished product inventories.

The basic EOQ model assumes a one-time full replenishment of inventory. But in the case of inventory, when the producer and consumer of the inventory are the same, gradual replenishment occurs. If the rate of production is faster than the rate of consumption, then production takes up only part of the inventory development cycle. Their required level consists of the difference between production and consumption at the current time. Production stops when inventory levels reach the optimum level, and then only inventory consumption occurs. When the stock runs out, the cycle repeats.

Applied models for managing inventories of material resources (EOQ, ABC method).

The application of the EOQ model is based on formula (1.1) for calculating the optimal value of one order for restocking:

where EOQ is the optimal size of inventory purchase in physical units;

Q - assessment of stock consumption for the budget period (quarter) in physical units;

O - transaction costs for the order: reporting, negotiations, settlements;

C - warehouse and immobilization costs for the stock during the budget period (quarter).

The purchase cost is not included in the formula, since it contains the answer to the question not “who to buy from,” but “how much to buy.” In other words, the use of this model fits precisely into the concept of operational management within the framework of the budget assignment

This system is based on choosing a lot size that minimizes the total cost of inventory management. The latter consist of order fulfillment costs and inventory holding costs.

Fulfillment costs are overhead costs associated with fulfilling an order and depending on the size of the order. In industry, these costs are allocated to preparatory and final operations. In its classic form, the EOQ model is rarely used in practice, because it contains quite bold “simplifications”. So, firstly, it is assumed that the production consumption of goods and materials is set in advance and very evenly throughout the entire budget period and, secondly, such an important logistics factor as the time from the moment of order to the receipt of inventory at the enterprise warehouse is not taken into account. And finally, the most important thing is that in the simplified EOQ model, when calculating total costs, only production costs (an efficiency criterion) are taken into account, and indirect probabilistic costs of changes in financial stability are not taken into account. In the practical activities of enterprises, as a rule, a complicated EOQ model is used, taking into account the need to constantly have a minimum amount of stock in stock in case of unforeseen circumstances (a “surge” in market conditions, which will force them to switch to the maximum production mode, or a delay for some reason in the next batch of deliveries) etc.). This minimum reserve (let's call it NZ - emergency reserve) provides the company with a certain “margin of safety” against force majeure circumstances. In the EOQ model with the introduction of the margin of safety factor, there are four additional parameters:

Time from the moment of order to the receipt of inventory at the warehouse (or to production);

Daily consumption (or sales);

NZ value, constantly in the company's warehouse;

The inventory level signaling the need to supply a new order - OR (order point).

The amount of emergency stock is determined based on how significant the production (or supply) of a particular type of product or inventory is. When introducing the labor cost factor into the model, a category such as the probable costs of stopping production (due to the lack of inventory of goods and materials in the warehouse) is included in the calculation. As the NC increases, the probability of “cycle stopping” decreases. The probability of production interruption is calculated based on historical data on daily consumption and delivery time. The shutdown probability data is applied to each purchase order (since the production shutdown probability occurs before each delivery of the order). At the same time, on the basis of the model, the optimal value of the NC is calculated, at which the total costs (maintaining and not maintaining the NC) balance each other.

A purchase order is placed when the stock on hand is reduced to the reorder point. Once an order is placed, inventory continues to decrease as the ordered product is transported over a period of time t (order lead time). The amount of stock at the order point should be chosen such that in a working situation during time t the stock does not fall below the insurance value. In the event of an unexpected increase in demand, the safety stock will begin to work. In this case, an additional delivery must be made. Such a control system provides protection against the occurrence of shortages.

This system involves a continuous recording of inventory balances to determine the reorder point.

In practice, a stock control system with a fixed order size is used in cases of:

Large losses due to lack of stock;

High costs of storing inventory;

High cost of the ordered goods;

High degree of demand uncertainty;

Price discounts depending on the quantity ordered.

When using the system, inventory control with a fixed order frequency is carried out at regular intervals by conducting an inventory of balances. An order for the supply of a new batch of goods is drawn up based on the results of the inspection. The size of the ordered batch is determined by the difference between the maximum inventory norm and the actual remaining quantity. It takes time to fill an order, so it is necessary to increase the batch size by the amount of expected consumption during this time. The size of the ordered batch can be determined by the formula:

where Q is the size of the ordered batch;

Zmax - the maximum reserve provided for by the norm;

Zf - actual stock at the time of inspection;

Zt is the stock that will be used up during the placement and execution of the order.

The demand intensity of this model is the magnitude of the variable. The order is carried out at regular intervals. But the size of the ordered batch will be different in different periods. This system is used when it is possible to order lots of different sizes. A feature of this system is the possibility of shortages. It occurs when demand increases because inventory runs out before the order deadline.

It can be noted that an inventory control system with a fixed order frequency is used in the following cases:

If it is possible to receive an order in batches of different sizes;

With relatively low costs for placing an order and its delivery;

With relatively small losses from a possible shortage.

No less promising in the development of combined methods is the involvement of administrative and organizational resources. Bearing in mind the active involvement of marketers, in terms of forecasts (current and operational), as well as distributors (dealers, agents, sales managers, etc.) and their expert assessments of future sales volumes.

Based on this, it is possible to develop a block diagram for the formation of an inventory management model; it is presented in Fig. 1.1. The main strategy is a replenishment model with constant frequency and variable order quantity.

Fig.1.1.

The latest innovation in the field of production (differentiation of products at the latest possible stage of production on the basis of the most similar components; use of the benefits of mass production not at the assembly stage, but at the stage of manufacturing components; the desire to maximize customer satisfaction at the stage of selecting goods for production) require its flexibility at the shop level, achieved both through expanding the ability to change equipment and through the use of new inventory management methods.

One of the methods for reducing inventories, increasing production flexibility and the ability to withstand increasing competition has become the Just-in-Time method, which has become most widespread in the USA and Western European countries. This method, which radically transformed traditional ideas about production management, including inventory, has its roots not only in the economic sphere, but also deeper - in the sphere of consumption of finished products. With the introduction of the Just-in-Time method into the practice of companies, customer requirements, sales strategy and production economics were linked with the planning and management of the production process.

The fundamental idea of ​​this method is based on three premises, the correctness of which has been empirically confirmed many times.

Firstly, it is assumed that requests from consumers of finished products should be awaited not by their stocks, but by production facilities ready to process raw materials and supplies that come almost “from the wheels.” As a result, the volume of inventory, considered as frozen capacity, is minimized.

Secondly, in conditions of minimal inventories, continuous rationalization is necessary in the organization and management of production, because a high volume of inventories eliminates errors and shortcomings in this area: production bottlenecks, unsynchronized operations, used production capacities, unreliable work of suppliers, as well as other shortcomings are eliminated to the background.

Thirdly, to assess the efficiency of the production process, in addition to the level of costs and productivity of funds, one should include the deadline for the implementation of the application, the so-called duration of the full production cycle. Short deadlines for the implementation of applications facilitate enterprise management and contribute to increased competitiveness due to the ability to flexibly respond to changes in external conditions.

These prerequisites lead to the requirement for a maximum reduction in the duration of the production cycle, which is achieved through:

Reducing working capital inventories and continuous production;

Reducing the volume of production and transported batches;

Proper placement of workplaces and transport routes;

Changes in the designs of machines and equipment and personnel training in order to minimize the time required for technical re-equipment of production.

When applying the Just-in-Time method, the production process considers the logistics chain, which represents the passage of material flow from suppliers to consumers through the next stages of processing.

In conventional, non-consumption-oriented production planning and management, there are three separate parts: supply cooperation, production process management and product sales. In the Just-in-Time system, all of the listed elements create an integral hierarchical whole. In contrast to traditional management methods, according to which the central link of production planning issues production tasks to all departments and industrial units, with the Just-in-Time method, central planning concerns only after the supply chain link, i.e. finished goods warehouse. All other production and supply units receive orders directly from the next (located closer to the end) link in the logistics chain. For example, a warehouse of finished products has submitted an application, which is equivalent to issuing a production task for a certain number of products to the assembly shop; the assembly shop gives orders for the production of parts to the processing shops and the cooperation department, etc. (Fig. 1.2).

Rice. 1.2. Production management: a) in the traditional system; b) the “Just in time” system

A production order is always issued to the department that uses (or processes) the part. Thus, the material flow from the “source” to the “consumer” is preceded by the flow of information in the opposite direction. Just-in-time production is preceded by just-in-time information. The elements connecting the flows of materials and information in intermediate links are index cards. If in traditional management systems the same index card accompanies a container with parts as it passes through successive links in the logistics chain, then with the Just-in-Time system, each intermediate link has at its disposal a whole set of cards, the number of which is equal to the number of containers. Sending a card containing the necessary information from the “consumer” to the “source” is equivalent to issuing a production task, which fully obliges the “source” to begin its implementation in accordance with the data contained in the card.

Since the role of centralized planning in the Just-in-Time system is limited, the importance of the production task from the “consumer” to the “source” increases enormously. This practically means that the implementation of planned tasks (relating to finished products) is carried out very accurately, sometimes even at the expense of overtime.

As you know, the success of products on the market and, consequently, the success of an enterprise in a modern economy depends, first of all, on three factors: innovation, productivity (efficiency) and product quality.

If the problems of innovation are, in principle, outside the scope of the Just-in-Time strategy, then labor productivity and product quality are directly related to it. The requirement for efficiency and maximum reduction of production cycle time leads to the need to eliminate interoperational control points. At the same time, the requirements for the quality of finished products are increasing. The most modern technology comes to the aid of new ways of organizing production. Touch sensors of shape and parameters, operating on the basis of information processing, installed on automated and robotic workstations, allow for 100% quality control of parts.

At the same time, in those areas of the production process where the use of modern measuring technology solutions is not yet possible, self-control systems, supported by appropriate material incentives, are used as a transitional stage. Firms implementing the Just-in-Time strategy usually start with a dedicated production site, and after gaining appropriate experience, they extend the use of this method to subsequent sites and enterprises. Foreign experience shows that companies that have adopted this method, as a rule, do not deviate from it and do not return to traditional methods of production management.

Practice shows that for the effective implementation of the Just-in-Time strategy, it is necessary to change the way of thinking of the entire team involved in production and sales issues. The traditional “more is better” mentality must be replaced by “less is better” when it comes to inventory levels, production cycle utilization or batch sizes.

Important tasks also face the management personnel of companies, who, on the one hand, must themselves be convinced of the advantages of implementing the Just-in-Time system, and on the other hand, must be able to convince lower-level management personnel of this. This is quite a difficult task, because... Usually, when implementing a Just-in-Time system, the requirements for labor discipline of all employees increase significantly.

Since the implementation of the Just-in-Time concept violates an essential information system, enterprises or firms associate the implementation of this concept with the development and implementation of a new system for collecting production data in the circulation of documentation, which, as a rule, refuses (partially or completely) paper information media in favor of open monitor communication.

The results of a detailed analysis carried out on the implementation of the Just-in-Time concept in Western European enterprises are impressive. Work-in-process inventories fell by more than 80%; finished product inventories - by approximately 33%. The volume of production inventories (materials and related parts) ranges from 4 hours to 2 days, compared to 5-15 days before the implementation of the Just-in-Time method. The productivity of the production cycle (the deadline for completing tasks of the entire logistics chain) decreased by approximately 40%; production costs - by 10-20%. Production flexibility has increased significantly.

The costs associated with the preparation and implementation and use of the Just-in-Time strategy are relatively small and, as a rule, they pay off already a few months later with proper functioning of the system.

Using the Just-in-Time strategy also provides other benefits, including non-economic ones. For example, the creation of a transparent structure of material flows in the form of intermediate links contributes to the widespread implementation of SIM-type technology.

The use of the principles of the Just-in-Time system also has a positive impact on the long-term investment policy of the enterprise, which in this case gives preference to machines and equipment associated with flexible automation of production, transport and control processes.

Firms often use mathematical models to select inventory levels by balancing pre-production costs or order fulfillment costs and balancing stock-out costs with inventory holding costs. Inventory holding costs include not only the cost of holding inventory, spoilage costs, and obsolescence costs, but also the cost of capital. In other words, the rate of return that could be obtained by pursuing other investment opportunities at equivalent risk.

Currently, inventory management systems are widely used, such as ordering systems MRP-1, MRP-2, and ORT, Kanban.

Briefly about them we can say the following.

MRP-1 (Material Requirements Planning) system. Production is planned based on the needs for the final product. This system is based on a simple principle: the starting point is the predictable (predicted) or known demand for the final product.

This takes into account:

Cash stock;

Ordered purchased semi-finished products, components (already planned production of semi-finished products);

An order intended to produce a series of previous products (intended for something else).

The time for the production of semi-finished products and the delivery time of purchased components are calculated.

This system allows you to coordinate and quickly adjust the actions of the company’s supply, production and sales structures, taking into account emerging changes, having powerful information support. Decision making in the system is made using various operations research methods. Set tasks for calculating the need for raw materials, materials, components, semi-finished products; on creating a production schedule, etc. are solved using mathematical models, information and software.

The greatest efficiency of the system is achieved using computers.

This system is adopted in inventory management:

Semi-finished products, components, spare parts, the need for which directly depends on the demand for the final product;

Items from the piece list that require computer processing.

The MRP-1 system requires significant costs for the preparation of primary data and places increased demands on the degree of their accuracy.

The main disadvantage of this system is that it does not provide a sufficiently complete set of data on other factors of the production process.

MRP - 2 system (Manufacturing Resources Planning). This new system allows you to expand the scope of use by taking into account the possibility of strategic planning and taking into account the necessary capacities (computer-aided design, process control, etc.).

Forecasting problems are solved by developing a forecast of the need for raw materials, supplies, and components separately for priority and non-priority orders (analysis of possible order completion times and inventory levels is carried out taking into account the costs of creating and storing inventories).

When managing inventory, this system processes and adjusts all information about the arrival, movement and consumption of raw materials and supplies, inventory accounting, and the selection of an individual strategy for controlling and replenishing inventory for each item.

Simulation modeling methods are widely used in this system. The software of this system includes:

Planning of production supply means;

Calculation of production schedule;

Control of the activities of production structures;

Management of sales of finished products and procurement of raw materials;

Functions of forecasting, electronic data exchange, obtaining financial statements.

This system has a shorter payback period and implementation period compared to MRP - 1.

When working under the Kanban system, the manufacturing plant does not have a complete production plan and schedule for its implementation. A specific order from a consumer enterprise optimizes the work of the manufacturer within the limits of this order. The system operates on the principle of direct replenishment, but with a very small stock batch size. The production schedule is generated by circulating Kanban cards. The system functions as a coupon order for products and allows you to fully implement the “just in time” principle.

When suppliers are removed geographically, the order card is replaced by a message via the integrated information system. This principle places high demands on the consumer-supplier chain and the supplier’s logistics system. With this system, special requirements are imposed on the supplier - a guarantee of “just in time” delivery. At the same time, the number of suppliers is reduced by two or more, and long-term relationships are established with suppliers. The main company provides assistance to suppliers, especially in improving the quality of the products they supply.

The Kanban system is used in inventory management:

With a short delivery (production) period, the export of which is characterized by great flexibility in quality and layout (high requirements for reliability of delivery or production times);

Small in size, the supplies are placed in containers as intermediate stock at the workplace.

The OPT (Optimized Production Technology) system is designed to organize production and supply. In fact, this is a computer version of the Kanban system, which allows you to prevent bottlenecks in the supply-production-sales chain.

The ORT system is based on the principle of identifying bottlenecks in production, called critical resources. Stocks of raw materials and materials can act as critical resources; cars and equipment; technological processes and personnel. The effectiveness of the economic system as a whole depends on the effectiveness of their use.

The effect of this system is to increase the yield of finished products, reduce transportation and production costs, reduce inventories of work in progress, shorten the production cycle, reduce the need for warehouse and production space, etc.

The ordering system is used in the inventory management system:

Products for which it is impossible to determine the current demand, but the availability of stocks of which is important (spare parts for machine mechanisms, etc.; final products in conditions of market unpredictability with very short delivery times, etc.);

Cheap, generic goods with relatively low inventory holding costs (low rent, low risk, and do not require large storage space);

Products for which the needs are difficult to determine (products with variable write-off percentages, etc.).

Inventory management consists of solving two main tasks:

Determining the size of the required stock (stock norm);

Creation of a control system over the actual size of the stock and its timely replenishment in accordance with the norm.

Various methods are used to determine inventory standards.

Heuristic methods are used in determining the minimum quantity of inventory by studying the forecast of demand development based on the experience of a specialist. The specialist may be an employee of an enterprise involved in stock rationing. In this case, the experimental-statistical method and the method of expert assessments can be used.

The essence of the method of technical and economic calculations is to divide the total stock, depending on the intended purpose, into separate groups (nomenclature items, in trade - assortment items). Next, insurance, current and seasonal reserves are calculated separately for the selected groups. This method allows you to fairly accurately determine the size of inventory, but it is labor intensive.

Economic and mathematical methods. The demand for goods or services is most often a random process. It can be described by methods of mathematical statistics. One of the most common and simple methods used to determine the value of reserves is the extrapolation method. It allows you to transfer the rates that developed during the formation of reserves in the past to the future.

International practice of inventory management provides data that the growth rate of inventories should lag slightly behind the growth of demand, i.e.:

where Tz is the growth rate of inventory;

That is the growth rate of demand.

Order planning can be operational, tactical, or strategic. To determine the required order sizes, the following methods are used:

Step-by-step planning - covering a specific need for orders over a limited period of time;

Periodic planning - carried out for a certain period of time, taking into account the economic order quantity model. The method takes into account inventory holding costs, but the economic order quantity model is effective only when demand is stable;

Floating planning - inventory requirements are expressed in variable quantities, rather than in exact standards for a certain period, as in the basic economic order quantity model.

Over the past 15 years, many models have been developed in industrialized countries relevant to various inventory management issues. With the help of simulation, the effectiveness of the measures applied within a production or production program is proven, since the periods of passage of a product through the entire production line can be measured. Using simulation, it is also possible to test the designs of flexible production participants served by automated vehicles and estimate the costs of logistics for production.