Determining the need for material resources. Material requirements planning calculation calculation estimate
Types of requirements for materials. The need for raw materials and materials is understood as their quantity required to a certain period for a specified period to ensure the implementation of a given production program or existing orders.
The need for materials for a certain period is called the periodic requirement. It consists of primary and secondary.
Primary refers to the need for finished goods, assemblies and parts intended for sale, as well as purchased spare parts. Calculation of the primary need is carried out using the methods of mathematical statistics and forecasting, giving the expected need. The risk of an incorrect assessment or an inaccurate forecast of needs is offset by a corresponding increase in safety stocks.
The primary need is the basis of material flow management in enterprises operating in the field of trade. For industrial enterprises, the primary need should be decomposed into secondary components, such as components, parts and raw materials.
Example 1
The furniture factory produces work tables for completing kitchen furniture. The sink is located in the table, which in turn is completed with a mixer for cold and hot water.
The need for a sink and faucets is called secondary, since it can be determined from the primary need (number of work tables). If sinks and faucets are supplied in trading network as necessary spare parts, then there is both a primary and a secondary need for these products.
When calculating dependent requirements, the following are assumed to be specified: primary requirement, including information on volumes and terms; specifications or applicability information; possible additional deliveries; the amount of materials at the disposal of the enterprise. Therefore, deterministic calculation methods are used to determine dependent requirements. If this method of establishing the need is not possible due to the lack of specifications or the insignificant need for materials, then it is predicted using data on the consumption of raw materials and materials.
The production need for auxiliary materials and wearing tools is called tertiary. It can be determined from the secondary based on indicators of the use of materials ( deterministic definition needs), by carrying out stochastic calculations based on the consumption of available materials or by expert means.
Under gross requirement understanding of the need for materials planning period regardless of whether they are in stock or in production. Respectively net - need characterizes the need for materials for the planning period, taking into account their available stocks and is obtained as the difference between the gross - the need and the available warehouse stocks by a certain date.
Example 2
Let one of the items of materials have both primary and secondary requirements. In this case, it could be assembly units, which are used as components in the manufacture of a product (secondary requirement), and are supplied to the market in the form of spare parts (primary requirement). Table 1 shows that gross demand is determined from primary and secondary requirements. There are 450 units in stock. material. Net requirement is 650 units. (1100 - 450). To determine the net need for a certain period, a volume is subtracted from the warehouse stocks every time, not exceeding what is necessary to satisfy it. So, by periods: period 1 - net - there is no demand, since stocks exceed gross demand; period 2 - net - there is no demand, stocks at the beginning of the period are 210 units. (450 - 240); period 3 - the amount of cash on hand is 50 units. (210 - 160) and net - demand - 170 units. (220 - 50).
Table 1
Calculation of gross - and net - requirements
In practice, the total requirement for materials increases relative to the gross indication for the additional requirement due to defects in production and maintenance and repair of equipment. After comparison with the amount of available stocks, the residual requirement is adjusted by the amount of current stocks.
Methods for determining needs. Necessary condition effective management material flows is the knowledge of needs for the future. To determine it, one can use following methods:
Deterministic calculation in accordance with the production plan and available specifications for manufactured products;
Forecasting needs by extrapolating data on the use of materials for the future using methods of mathematical statistics;
Subjective assessment based on expert opinions.
Deterministic Methods are used to calculate the dependent requirements for materials with known primacy. With the analytical approach, the calculation proceeds from the product (its specification) along the hierarchy levels from top to bottom. The synthetic method involves calculations for each group of parts based on the degree of their applicability at individual levels of the hierarchy.
The stochastic calculation method allows you to set the expected demand based on forecast estimates based on data from the past period. For this purpose, the approximation of average values, the method of exponential smoothing and regression analysis are used.
Average Approximation used in environments where material demand fluctuates from month to month with a steady average.
Forecasting by this method is a procedure of averaging the past values of material requirements. In this case, the weight of each of the demand values can be the same (simple average calculation method) or different if fresh data has a greater weight (moving average calculation method).
Exponential smoothing method used in the case when forecasting the process of changing the need for material resources is made on the basis of the levels of a series of dynamics, the weights of which decrease as the level is expected from the moment of the forecast. For this circuit, a constant smoothing coefficient a is introduced into the calculations, the value of which is chosen in such a way as to minimize the forecast error.
The forecast equation, taking into account exponential smoothing, is written in the following form:
yt+1 = ayt + a(1-a)yt-1 + a(1-a)2yt-2 + … + a(1-a)kyt-k + … + (1-a)ty0,
where y0 is a value that characterizes some initial conditions
Regression analysis involves the approximation of known trends, the consumption of material resources using mathematical functions that can be extrapolated to the future period. In accordance with the nature of the dependence, linear and non-linear regression analysis are distinguished. The method of linear regression is advisable to apply with a conditionally proportional increase in consumption. If the demand curve is not approximated by a straight line, then a non-linear regression analysis is applied.
Methods of material support. Order method. Material support based on planned targets.
Different types of raw materials and materials, unequal conditions of their consumption and destination in certain sectors of the national economy predetermine the need to use different methods for calculating the need for them in order to obtain correct results. The most common and reliable is the direct counting method, in which the need for material (P) is determined by the following formula:
where n ij - the rate of consumption of material for the production of products, in physical units;
n j - program for the production of products in the planned period.
As a rule, the same material is consumed for the manufacture of several products. Therefore, a system of linear equations can be applied in the calculation.
The direct counting method has a number of varieties depending on the data used in the calculations.
The detailed method is used in cases where consumption rates for the production of specific parts and programs for their production in the planning period are used. It is used in intrashop planning, mass production of component parts, and in a number of other cases.
However, at enterprises with a multi-product nature of production, as well as in a number of associations with a large number of items of manufactured products, this method can also be very cumbersome. Plans are established in this case for a group of homogeneous products (for example, for a group of different sizes, but the same in appearance bearings, radio products, etc.).
In this case, the need is determined by typical representatives according to the formula
P tt = n type ∙ N,
where P tt - the need for material;
n type - consumption rate of a typical representative of this group of products;
In this case, a product is installed as a typical representative, the consumption rate of which approaches the weighted average rate for a group of products.
A variant of the direct counting method is the calculation of demand by analogy. It is used when it is planned to manufacture new types of products for which consumption rates have not yet been developed. In this case, the total need for a given material (P) is found by the following formula
P = k ∙ n an ∙ N
where k is a coefficient that takes into account the change in the consumption rate of a given product compared to a similar one;
n en - consumption rate of similar products equated to this product;
N is the program for the production of products in the planned period.
The quality and reliability of calculations in this case are largely determined by how well a similar product is selected.
Varieties of the method of direct counting are not limited to this. Many types of products Food Industry are made not from any one material, but from several. In order to obtain products with a predetermined quality, recipes are developed, they indicate the percentage of each material that is consumed for the production of these products. When using the calculation of the recipe composition, the need for suitable products is initially determined in accordance with the production program, which is established by multiplying the draft weight of one product by the production program for manufacturing products in the planning period. Then the total amount of materials that must be released into production is determined, taking into account losses in technological process(P O PT). In general, these calculations are carried out according to the formula
P O PT \u003d R ABOUT /k ABOUT,
where k OB - output coefficient finished products, which takes into account losses at all stages of the technological process of manufacturing products.
In industries and in individual industries where finished products are obtained as a result of chemical reactions, formulas for chemical reactions, molecular weights of the finished product and materials, as well as data on losses in the technological process can be used to calculate the need for raw materials and materials. AT general view these calculations are carried out according to the following formula:
where R M - the need for the source material for the planning period in natural units of measurement;
N - the program for the production of finished products, in natural units of measurement;
M M - molecular weight of the material;
M PR - molecular weight of the finished product;
k P - the total number of losses in the process of manufacturing finished products,%.
The need for each specific material is determined by the formula
R M = R OPT ∙ k M,
where k M - specific gravity this material in the general composition of the mixture for the manufacture of products according to the recipe.
In addition to the main ones, enterprises also consume auxiliary materials, the consumption of which is regulated not by the consumption rates per unit of manufactured products, but by the terms of wear. Such material resources include spare parts for machinery and equipment, inventory, tools and fixtures, various types of overalls, etc. At the same time, standard periods of wear and tear can be set not only in time, but also in units of work performed - in kilometers of run, ton-kilometers cargo work etc.
To determine the need for such materials, it is necessary to divide the number of products or parts that must be in operation by the standard wear periods.
In the absence of information to determine the need for materials by calculation, you can use the statistical data on the actual consumption in past periods, taking into account the changes that will occur in the planning period.
The simplest is the method of dynamic coefficients. To determine the need for material (R), it is necessary to multiply the data on its actual consumption in the past period (R f) by the coefficient of change in the program for the production of products or the amount of work in the planning period (k PR) and by the coefficient that takes into account the savings in material resources in connection with the introduction relevant organizational and technical measures (k e)
R = R F ∙ k PR ∙ k E.
More accurate results are obtained by the method of extrapolation of statistical data on the actual consumption of materials in the corresponding past time periods. For this purpose, data for several periods are analyzed and the main trends in the dynamics of changes in demand for subsequent periods are established.
In the extrapolation method, mathematical statistics and probability theory are widely used. At the same time, an important problem in these calculations is correct definition forms of the curve expressing the trend of change in demand over time.
When choosing the type of curve that best reflects the dynamics of change in demand, it is necessary to find the agreement criteria based on the analysis of deviations of empirical data from theoretical ones. Most of all, this will correspond to such a curve, the fit criterion of which is the most optimal. To predict the need for material resources, you can use multivariate analysis models. In this case, the factors that affect the magnitude of the need are analyzed, which can be written in the following form:
y \u003d f (x 1, x 2, ..., x n),
where y is the need for material for the prospective period;
x 1 , x 2 , ... , x n - factors influencing this need.
When determining the need for materials of enterprises and associations, such an analysis can be subjected to: the structure and magnitude of production for the planned period; the dynamics of changes in consumption rates and tasks for saving materials, the timing of product wear, the introduction of new, progressive materials and substitutes, etc.
The reliability of the determined need based on the methods discussed above, which are based on historical data on the consumption of materials in past periods, is significantly increased if they are combined with expert assessment methods. Their essence lies in the fact that the dynamics of changes in demand is established or specified on the basis of a survey of specialists in the field of logistics. To this end, special questionnaires are being developed in which questions are formulated regarding factors and the general need for materials. Summarizing and taking into account the opinions of specialists can have a significant impact on the accuracy of forecasts.
The concept and functions of procurement logistics
Procurement logistics is the process of providing enterprises with material resources, placing resources in the warehouses of the enterprise, storing them and issuing them to production.
The purpose of procurement logistics is to meet the production needs for materials with the greatest possible economic efficiency. In doing so, the following tasks are solved:
- Maintaining reasonable terms for the purchase of raw materials, materials and components.
- Ensuring that the quantity of supplies exactly matches the needs for them.
- Compliance with production requirements for the quality of raw materials, materials and components.
Without purchasing logistics, the normal operation of the enterprise is impossible. It is a link between different producers and coordinators of their work.
Procurement logistics performs the following functions:
- formation of a strategy for the acquisition of material resources and forecasting the need for them;
- receiving and evaluating proposals from potential suppliers;
- selection of suppliers;
- determination of the needs for material resources and calculation of the quantity of ordered materials and products;
- agreeing on the price of ordered resources and concluding supply contracts;
- control over the delivery of materials;
- input quality control of material resources and their placement in the warehouse;
- bringing material resources to production units;
- maintenance of stocks of material resources in warehouses at the normative level.
The described functions are implemented by the logistics service (purchasing department) in close relationship with other departments of the enterprise: marketing department, production, pre-production service, accounting, financial and legal departments.
Increasing role of purchasing
logistics in modern conditions
Transition to market economy defines the role and growing importance of purchasing logistics in social production. Market conditions brought to life a number of significant changes in the field of logistics of production. Among them, the most important were:
- the pressure of a rapidly growing range of products requested by the market;
- reduction of time of implementation in production new products, accelerating the expansion of the range;
- reduction of the duration of the production cycle;
- aggravation of competition between manufacturers against the backdrop of market saturation with the necessary goods.
All these changes have led to the fact that the various activities of the enterprise - production, economics, financial activities became increasingly dependent on the state of logistics. It turned out that there are large areas of inefficiency in the supply chain, the rationalization of which can lead to large savings. There was a need to implement new approaches to organizing the processes of material support for production and management.
2.1.2. Acquisition process
materials and its main stages
The process of acquiring materials includes a number of logical interrelated species works. The following stages of the process of acquiring materials are distinguished:
Drafting applications. Applications for the purchase of materials are prepared by the relevant employees of the functional divisions of the enterprise. They contain information about what types and quantities of materials the company needs, when they should be received and who made the request. Applications are drawn up in such a way that the quantities of materials expected to be received outstrip the actual requirements for them.
The time between the placement of applications and the receipt of materials is called lead time. Employees responsible for compiling requisitions should set the delivery dates of materials with a minimum lead, taking into account the capabilities of the supplier and the needs of the consumer of materials.
Application analysis. Applications for the consumption of materials are analyzed in the logistics service with the participation of specialists from other departments. The purpose of the analysis is to ensure minimum costs for each type of materials, the specific consumer properties of which are supposed to be used in the production of products. Research methods are functional cost analysis and cost construction.
The analysis should answer the following questions:
- Can cheaper materials meet the needs of production?
- Are these needs justified?
- Can other types of materials meet the identified needs?
- Is it possible to simplify the design of the manufactured product?
- Is the supplier able to reduce the cost of materials by participating with the consumer in the development of the product or by analyzing the received specifications?
The supply service has no right to replace the materials specified in the applications. Department employees should analyze incoming requests and offer such options for purchasing materials that can lead to a decrease in the cost of orders.
Choice of suppliers. When choosing suppliers, the main criteria are: reliability of the supplier, the ability to supply the necessary resources of proper quality and on time, the supply of material resources as soon as possible minimum prices, remoteness of the supplier from the consumer, availability of free capacities of the supplier, etc.
The main sources of information about suppliers and materials are personal contacts with "sellers", advertisements in advertising publications, descriptions of goods that are given in catalogs and prospectuses, visits to enterprises and studying the practice of supplying products, information received from banks, trade associations, public institutions etc.
From the list of suppliers with a strong reputation, those who offer the most favorable conditions in terms of price and delivery time are selected. It is advisable to distribute large orders between two or more suppliers in order to check the competitiveness of the main supplier and protect yourself from possible surprises.
Placement of orders. The purchase of materials is carried out different methods depending on the type of materials and components. The main procurement methods are:
- bulk purchases (one large batch at a time);
- regular purchases of materials (the buyer orders the required amount of materials that are supplied to him in small lots over a certain period);
- daily (monthly) purchases (used when purchasing cheap and quickly used materials);
- obtaining material as needed;
- single purchases (material is ordered if it is required and taken out from suppliers' warehouses in cases when it is impossible to receive material as needed).
An order is documented through the conclusion of a contract between the supplier and the consumer of the material.
Basic elements of a contract.
- Offer and acceptance of the offer. A contract is drawn up if one party offers a certain batch of goods at a specified price, and the other party accepts this offer.
- Financial conditions. The contract must have a value, i.e. it becomes a contract in the legal sense only when financial terms are stipulated in it.
- The right to enter into contracts. Only certain officials(director, CEO) authorized by the enterprise and acting on its behalf.
- Legality. The contract must be legal, i.e. fully comply with the legal norms of the country.
The structure of the contract provides for the definition of the subject of the contract, an indication of the quality and quantity of goods, the amount of the contract, the procedure for the delivery and acceptance of goods, the responsibility of the parties, the procedure for resolving disputes.
Order fulfillment control. The size of the orders and the duration of the period during which these orders are fulfilled are controlled by the Procurement Department. At the same time, it is possible to adjust the schedules for the supply of materials and the corresponding refinement of schedules for the release of products.
Completion of the acquisition process. Receipt of ordered materials in strict accordance with the terms of the contract is a necessary sign of the completion of the transaction. The acceptance of products is important, during which it is necessary to make sure that the material has been delivered:
- the required quality;
- in the right amount;
- at the appointed time;
- for the agreed price.
Purchase and sale are properly documented. Documenting Delivery involves receiving a shipping notice and a cover letter from the supplier stating the quantity of goods and the time of delivery. The receipt of materials at the warehouse is documented by the appropriate invoices and recorded in the goods registration book.
2.1.3. Determination of material requirements
Types of material requirements
Under the need for raw materials and materials is understood as their quantity required by a certain date for a specified period to ensure the implementation of a given production program or existing orders.
The need for materials for a certain period is called periodic need. It is made up of primary, secondary and tertiary.
Under primary the need for finished products, assemblies and parts intended for sale, as well as for purchased spare parts, is understood. Calculation of the primary need is carried out using the methods of mathematical statistics and forecasting, giving the expected need. The risk of an incorrect assessment or an inaccurate forecast of needs is compensated by a corresponding increase in safety stock.
The primary need is the basis of material flow management in enterprises operating in the field of trade. For industrial enterprises, the primary need should be decomposed into secondary components.
Under secondary understands the need for component parts, parts and raw materials necessary for the production of finished products.
Example 2.1.1. The furniture factory produces work tables for completing kitchen furniture. The sink is located in the table, which, in turn, is completed with a mixer of cold and hot water. The need for a sink and faucets is called secondary, since it can be determined from the primary need (number of work tables). If sinks and faucets are supplied to the distribution network as necessary spare parts, then there is both a primary and a secondary need for these products.
When calculating dependent requirements, the following are assumed to be specified: primary requirement, including information on volumes and terms; specifications or applicability information; possible additional deliveries; the amount of materials at the disposal of the enterprise. Therefore, deterministic calculation methods are used to determine dependent requirements. If this method of establishing the need is not possible due to the lack of specifications or the insignificant need for materials, then it is predicted using data on the consumption of raw materials and materials.
Under tertiary the production need for auxiliary materials and wearing tools is understood. It can be determined based on the secondary on the basis of indicators of the use of materials by conducting stochastic calculations based on the consumption of available materials or by expert means.
Depending on the accounting of cash reserves, there are gross- and net material requirements.
Under gross need is understood as the need for materials for the planning period, excluding stocks in the warehouse or in production. Accordingly, under net need the need for materials for the planning period is understood, taking into account available stocks. It is defined as the difference between the gross demand and the inventory on hand by a certain date.
In practice, the total need for materials increases relative to the gross indicator by an additional need due to defects in production and maintenance and repair of equipment. After comparison with the amount of available stocks, the residual requirement is adjusted by the amount of current stocks. Ratio various kinds requirements for materials is shown in fig. 2.1.1.
Rice. 2.1.1. The ratio of different types of material requirements
Methods for determining needs
A necessary condition for the effective management of material flows is knowledge of the needs for the future. The methods used to determine it are shown in fig. 2.1.2.
Rice. 2.1.2. Classification of methods for determining needs
Deterministic calculation methods are used to calculate the secondary requirements for materials with a known primary. At analytical method the calculation proceeds from the product specification down the hierarchy levels from top to bottom. Synthetic method involves carrying out calculations for each group of parts based on the degree of their applicability at individual levels of the hierarchy.
Stochastic calculation methods allow you to set the expected demand based on numerical data characterizing its changes over a certain period of time. For this purpose, use approximation of mean values, exponential smoothing method and regression analysis.
Average Approximation used in environments where material demand fluctuates from month to month with a steady average. Forecasting by this method is a procedure of averaging the known values of the demand for materials.
Exponential smoothing method are used in the case when the forecasting of the process of changing the need for material resources is based on the levels of a series of dynamics, the weights of which decrease as the given level moves away from the moment of the forecast. For this purpose, a constant smoothing coefficient a is introduced into the calculations, the value of which is chosen in such a way as to minimize the forecast error.
Regression analysis involves the approximation of known trends in the consumption of material resources using mathematical functions that can be extrapolated to the future period.
2.1.4. Providing production with materials
In the practice of enterprises, several methods of planning the material support of production are used (Fig. 2.1.3).
Rice. 2.1.3. Methods for planning the material support of production
Custom method assumes that the required material is purchased only when a requirement arises, so no stock is created. This method is used in single and small-scale production to fulfill the need for high-quality materials and bulky parts, which are difficult to store, as well as materials for repair work.
Order-based material supply is possible for single or multiple items. In the latter case, it is carried out at regular intervals, for example, weekly intervals, when a single order is formed, taking into account all applications received during this period.
Material support based on planned targets. This method based on a deterministic calculation of material requirements. In this case, it is assumed that the independent requirement for a certain period, the product structure in the form of specifications, which makes it possible to determine the dependent requirement, and the possible additional requirement are known.
When supplying materials based on planned targets, the order size is determined based on the net requirement, taking into account the planned receipt and the availability of materials in the warehouse.
Let us explain the concepts of warehouse, planned and workshop stock.
Warehouse stock- this is the amount of materials intended for industrial consumption and available according to the data accounting. In order to determine the real need for materials, the warehouse stock is divided into two parts: materials that are available for the planned release program, but are not yet in demand by the shop, and materials that can still be obtained (available stock).
Intended stock is the amount of materials intended for sale and therefore not considered as available.
shop stock- these are materials received from the warehouse and located in the workshop for the purpose of further processing.
Material security based on consumption involves the timely replenishment of stocks and maintaining them at a level that would cover any need before a new receipt of materials. In accordance with the goal, the problem of determining the time of an additional order is solved, the issue of the size of the order is not considered.
Depending on the type of check and the rules for issuing additional orders, there are two methods of material supply based on the consumption carried out, known as inventory management systems:
- Ensuring timely orders (stock management system with a fixed order size);
- the necessary rhythm (a system of inventory control with a fixed frequency).
Within the framework of these methods, in turn, there are several possible variations, which are determined by the policy pursued in the field of maintaining stocks. They will be discussed in the topic "Inventory management".
2.1.5. Delivery Calculation Methods
Determining the Economic Order Quantity
An economic order size is a material lot size that will minimize the annual total cost of order fulfillment and material storage. The technique for determining the economic order quantity is to compare the advantages and disadvantages of purchasing materials in large and small quantities and to choose the order quantity that corresponds to the minimum total cost of restocking. The ratio of the size of the order and the cost of supply (fulfillment of orders) and storage of materials is graphically shown in fig. 2.1.4.
Rice. 2.1.4. The dependence of the cost of order fulfillment
and storage of materials from the size of the order
Let x be the number of units purchased as a result of one order. As the number of purchased items of material increases, the running costs of storing materials (holding inventory) increase (curve 2). At the same time, as the batch size increases, the number of orders per year decreases. This leads to a decrease in the costs associated with the execution of orders (curve 3). As can be seen from fig. 2.1.4, the curve of total annual expenses (curve 1) has a minimum at x = x 0.
Based on a quantitative assessment of the dependence of the costs of purchasing and storing materials on the amount of purchased material, it is possible to determine the size of the order that minimizes the value of the total costs under the following assumptions:
- the total number of material units that make up the annual stock is known.
- demand is unchanged.
- orders are executed immediately, i.e. orders are fulfilled on time, the lead time is known and constant.
- registration costs do not depend on their size.
- the price of the material does not change during the considered period of time.
In accordance with the assumptions made, the cost of order fulfillment and inventory maintenance can be expressed by the formula
where With 1 and With 21 - respectively, fixed and variable costs associated with the execution of the order and the content of materials;
n- the number of orders per year;
q/2 is the average stock.
where Q- annual material requirement.
The above formula establishes the economic order quantity for conditions of uniform and strictly defined (deterministic) inventory consumption. In the practice of the enterprise, there may be:
- delayed delivery; in this case, the material is delivered not one-time, but over a certain period of time with a certain intensity and is consumed by production evenly; its use begins immediately after the start of supplies before the entire supply is actually completed;
- accelerated use; in this case, the intensity of consumption of stocks is such that a shortage of material is possible.
Taking into account the noted special conditions private models are built to determine the economic order size.
Determination of the optimal production batch size
If the enterprise is its own supplier, then the problem of determining optimal size production batch, i.e. the quantity of products that must be manufactured to replenish the stock of its own components. The scheme of movement of the stock, typical for such a case, is shown in Fig. 2.1.5.
Rice. 2.1.5. Graph of the movement of the current stock
when replenishing materials for a finite interval
As can be seen from the figure, the consumption of the stock occurs gradually, during the entire cycle t, and its replenishment only during the period t 1 , the duration of which is determined by the manufacturing time of the produced batch (production cycle). The necessary components are started to be manufactured upon receipt of the corresponding order and, as soon as they are ready, they are immediately sent to the consumer: to the warehouse of the receiving shop for further processing or to the picking warehouse of the assembly shop. The daily replenishment rate is determined from the condition
where p- the annual volume of production of components.
If the rates of production (receipt) and consumption of materials are set, then the stock will grow during the entire replenishment period and will reach a maximum value at the end of it.
The maximum stock level will be
and the average stock will be
Considering that the replenishment period is determined based on the average daily production volume t 1 = 240q opt /p, the total annual costs associated with the replenishment and storage of materials will be
 |
(2.1.6) | order subject to wholesale discount
1.The need for materials - This the amount of matter, raw materials and components, which is necessary for the implementation of a given program of output, available orders.
The need for materials is:
→primary - the need for finished products, assemblies and parts for sale and for purchased spare parts. This need is driven by market demand. For its calculation, methods of forecasting and mathematical statistics are used.
the accuracy of these methods is offset by an increase in safety stock. This need is the main one for an enterprise engaged in trade;
→ secondary - the need for components, parts and cheese used for the production of products that constitute the primary need, i.e., finished products of the enterprise. For the calculation, deterministic calculation methods are used. The initial data are primary needs, specifications, data on the availability of resources in the warehouses of the enterprise. Dependent requirements calculations are used on industrial enterprises;
→ tertiary - the need for auxiliary material resources for production purposes. Wearing tools are an example of such thermal resources. The tertiary need is determined by deterministic calculation methods, stochastic methods, expert assessments based on secondary needs based on the consumption of available materials. The tertiary need is typical for industrial enterprises.
Depending on the accounting of available stocks of materials, the need for materials is classified:
→ on gross need - the need for material resources for the implementation of the production program without taking into account the availability of finished products and materials in stock. Gross requirement is determined by the sum of primary, secondary and tertiary requirements;
→ net need - the need for material resources for the "execution of the production program, taking into account the availability
finished products and materials in stock. Net requirement is determined by the difference between gross requirements and stocks.
Practically total need differs from the gross requirement due to defects in production, as well as due to repairs, Maintenance and preventive maintenance on equipment.
2. Example of calculating gross and net requirements based on primary, secondary needs and on-hand stock.
Let be one of the material positions has both primary and secondary requirements. In this case, we can talk about assembly units that are used as components in the manufacture of a product (secondary requirement) and are supplied to the market in the form of spare parts (primary requirement).
From Table. 1 shows that the gross requirement is determined from primary and secondary requirements. There are 450 units in stock. material. The net requirement is 650 units. (1100 - 450).
To determine the net need for a certain period, we subtract from the stock every time the volume that does not exceed the volume necessary to satisfy it. So, for periods: 1 - there is no net demand, since stocks exceed gross demand; period 2 - there is no net demand, stocks at the beginning of the period are 210 units. (450 - 240); period 3 - the amount of cash on hand is 50 units. (210 - 160) and net demand - 170 units. (220 - 50).
Allocate how many types of need for material resources. Let's consider them in more detail. The need for the planning period, regardless of whether the stocks are in stock or in the form of production reserves is called gross requirement.
Total Gross Demand- gross demand + additional demand, which includes experiments, samples, increase in demand associated with the repair and maintenance of equipment, a reserve in case of short deliveries.
Net requirement is pure need. It is defined as the difference between gross demand and available availability.
Primary- market need (what you need to sell on the market)
Secondary- raw materials, materials, semi-finished products, components that are necessary for primary needs.
Tertiary - auxiliary materials for other purposes, necessary for primary and secondary needs.
Material requirements planning is a procurement planning system taking into account seasonal trends and dynamics of primary demand, as well as the type of markets in which the company presents its products. When planning requirements, they use data on the amount of necessary stocks and the time they are received in accordance with the production plan, i.e. this system planning determines the quantity and schedule for the release of the required products. This planning system allows you to:
- ensure the availability of raw materials, materials, components in the required quantities;
- reduce the costs associated with ordering and storing inventory;
- increase the efficiency of scheduling and work in a constantly changing market environment.
The raw material requirement plan is a procurement schedule based on inventory availability and the expected order cycle.
Requirements planning system components:
- schedule of the main production process, which determines the amount of finished products broken down by time;
- data on the specific consumption rates of raw materials and materials, determining the amount and composition of raw materials and components necessary for the production of each specific type products;
- inventory data for each component, (quantity available, expected receipts);
- data on the main products that are purchased and all products that are produced by the enterprise itself;
- forecast of the need for materials in accordance with the schedule of the main production process;
- structured list of raw materials and materials;
- Inventory data, open orders, and lead times to calculate lead times and order quantities for materials.
Basic principles of planning requirements for raw materials and materials:
- coordination of needs for raw materials and materials (components) and a plan for the production of finished products;
- breakdown by time.
Consider three of the possible methods for determining the need for materials that are used in logistics:
- 1) deterministic- is used when a certain period of order fulfillment and the need for materials in terms of quantity and timing are known.;
- 2) stochastic- when the basis for the calculation are mathematical and statistical methods that give the expected demand .;
- 3) heuristic - the need is determined based on the experience of workers.
The choice of one of these methods depends on:
- enterprise profile;
- customer capabilities;
- product type;
- availability and type of warehouses.
Let's consider the first one deterministic . This method is used to calculate the need for materials and components to meet the needs of production, when sales volumes of products are determined. The deterministic method is based on the use of well-defined initial data and serves to determine secondary and tertiary needs with a known primary. Necessary information - primary need, including data on volumes and terms of production; information about the structure of the product in the form of a specification or instructions on the applicability of certain parts; cost rates for materials and types of products; available availability.
The calculation of material resources is carried out separately for social needs, main and auxiliary production, and economic and mathematical models can be used here.
The need for material resources for the main production:
M - need;
H - the rate of consumption of material resources i-ro names pa j type of product;
N- manufacturing program] product type; p - assortment.
Determining the need for material resources for repair and maintenance needs: 
T 0 - time to failure of equipment of this type;
R 0 - given level of reliability;
Qj - number of units. equipment of this type;
Well - the consumption rate mat. i-ro type for 1 repair t - delivery time;
L is the number of deliveries.
In a deterministic method, it is important to set the time of consumption of material resources. A cycle chart that fills from right to left can be useful here. The cycle is determined by the longest operation. Based on the cycle schedule, you can determine how many parts to run and when. In order to meet the order on time, the materials must be available as soon as possible, so that the cycle of their receipt and primary processing does not increase the production cycle of the product. Parts must be ready on time so that there is time for assembly. Purchased items must be ordered with the expected delivery time in mind.
Stochastic. Methods of this type are used in the calculation based on the amount of materials used. They are based on prediction. Forecasts can be medium-term (3-5 years), short-term and long-term. Forecasts based on stochastic models have the following features: the situation predicted for the future is based on the time of the forecast. Changing the time point affects the result of the forecast. Evaluation of the development of the phenomenon, as well as the collection necessary information carried out before the development of the forecast; the forecasting process relies on information about the past period.
Task.
A manufacturing agro-industrial enterprise needs to purchase containers for packaging products. It is known that 24 units of products are placed in 1 box. Determine the need for containers for December, if you know how many products were produced from June to November of the same year. The data are presented in the table.
Determination of demand by the method of "Naive forecast".
F-forecast next month,
D(t) - demand of the analyzed month.
Decision:
D(t)=920000/24=38333.3 boxes.
So, as we know that in the previous month the demand for packaging was equal to 38333.3 boxes, therefore, 38333.3 boxes must also be ordered for the month of December.
Determination of demand by the "Simple average" method.
Where F(t + 1) is the expected value of demand t is the month under study t + 1 is the next month t-1 is the previous month
- the weight of each of the n past values of demand (the same).
Decision:
Let us denote the demand for packaging in November D(t)=38333.3 boxes,
demand for packaging in October will be D(t-J)=956000/24=39833.3 boxes;
similarly calculate the demand for September D(t- 2)=1000000/24=41666.7 boxes,
August D(t-3)= 1116000/24=46500 boxes;
July D(t-4)= 1100000/24=45833.3 boxes;
June D(t-5)= 1105000/24=46041.7 boxes.
Substitute the values in the formula (2.4)
Therefore, 43035 boxes must be ordered.
Moving average method.
Used when it is understood that recent data is more important and therefore should have more weight, provided that the sum of the weights is equal to one.
Decision:
Let us substitute the known values of D(t) into formula (2.5). We get:
