Determination of needs

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Requirement determination (also requirement quantity planning , (material) requirement determination , procurement disposition ) describes in business administration the process of determining future material requirements according to time and quantity.

General

The needs assessment deals with the definition of the requirements for materials , semi-finished products or assemblies ( secondary requirements ) required for the manufacture of the products according to type, quantity, date and location. In this respect, this term is equivalent to the determination of secondary requirements; In practice, therefore, the term parts requirements determination is often used, in the literature material requirements planning . In the consumption-oriented determination of requirements, a distinction must be made between the order point method and the order rhythm method with regard to triggering the order process. The material required can be either procured externally ( components , external production ), or be prepared itself ( in-house production ). The tasks of material requirements planning therefore include the make-or-buy decision and, based on this, the long-term planning of the quantities of purchased parts and house parts, while the determination of requirements is more concerned with medium to short-term material requirements. On the basis of material planning, the production, procurement and transport capacities can be planned at an early stage. For production-related or economic reasons, the required parts, assemblies, etc. usually have to be manufactured or transported in larger lots . When calculating the lot size , not only the purchase prices and manufacturing costs but all relevant costs must be taken into account, such as transport, storage, set-up, interruption, information, communication, interest costs, etc.

Types of requirement

A distinction is made between three types of requirements: primary, secondary and tertiary requirements

Methods of assessing needs

There are basically four different methods of determining needs: deterministic , stochastic , heuristic and rule-based needs assessment. In the case of complex products with a long product life cycle and different sales markets , as is the case in the automotive industry, the methods can also be linked to one another in primary requirements planning, so that one can speak of a hybrid requirements determination.

Deterministic needs assessment

With the deterministic method, the dependent requirements are derived from the independent requirements with the help of parts lists or recipes . The primary requirement is initially in a market-related sales program and is then - especially if there are several production locations - transferred to several plant-related production programs, which are usually the starting point for determining requirements.

Typical fields of application

When customer orders should the entire job throughput time be less than the required delivery time. When calculating the lead time, the procurement time, the production time and the shipping time, including the storage times, must be taken into account. This is particularly important in production based on the BTO principle, in which the production program is derived from a sales program, as is common in the automotive industry, for example. The deterministic method is used for high-quality or customer-specific goods, some of which have a long replacement time. In principle, the deterministic determination of requirements should be aimed for, because this allows the secondary requirements to be determined exactly, thus keeping the inventory low and avoiding material bottlenecks. In operational practice, it is largely a problem because today all current P roduktions p lanungs- and - s control systems ( ERP systems ) are able to detect the secondary need for assemblies and parts on the basis of product structure data by BOM accurately. With this parts requirement, no batch sizes, stocks, production or transport times or the like have yet been taken into account.

Stochastic needs assessment

The basis of the stochastic method is the consumption values ​​of the past . These values ​​are statistically evaluated and updated in the form of forecasts for the future. The prerequisite for the application of stochastic methods is a sufficient database, i.e. That is, there must be enough information about past consumption. Stochastic methods are not suitable for new products and high-quality A-parts . They are conditionally suitable for spare parts if the database is large enough and the installed and still in use system is not taken into account. The required procurement time is longer than the required delivery time; the goods are low-value or standardized goods ( C and B parts ).

The requirements must be taken into account when selecting the respective process. In the stochastic determination of requirements, mathematical-statistical procedures based on probability theory are used:

see stochastics

If there is the possibility of consumption-based disposition and there is also a sufficient database, the use of stochastic methods is recommended, because there is a meaningful division of labor between people and IT systems and this reduces the routine work of the dispatcher. This way, a dispatcher has the opportunity to focus on problematic items, such as: B. Articles with fluctuating demand.

Heuristic needs assessment

With the heuristic method , the needs are determined by the subjective estimates of an experienced employee or expert, e.g. B. a dispatcher determined. This method is suitable for products, assemblies or parts for which there is insufficient data from the past. Alternatively, for new parts, e.g. Data from a similar part (e.g. previous part) can be used. For products, the requirements can be estimated using expected market shares. The disadvantage is that in the heuristic determination of requirements, each article has to be considered individually. With a large number of products or parts to be planned, an individual consideration of each article is therefore very time-consuming; therefore often only rough estimates are made. The resulting inaccuracies can be compensated for by safety stocks to ensure readiness for delivery .

Rule-based needs assessment

With the rule-based method (see rule-based system ), the secondary requirement is derived from the primary requirement using IF-THEN relationships. An example of this is found in the automotive industry, in which all possible variants of a vehicle model are described with the help of Boolean expressions in a complex parts list . The parts list can be evaluated on the basis of the product configuration of a vehicle: if a very specific equipment (trailer coupling) has been selected, then exactly the parts or assemblies required for it are selected from the parts list, but at the same time other parts or assemblies can no longer be required ( e.g. a cover cap).

Gross / net method

Under gross requirement of period-related total demand is to be understood, which is summarized in the secondary and tertiary demand and additional demand. The additional requirement is the requirement for scrap, wear, shrinkage or waste. This requirement is determined by adding a percentage to the secondary requirement or as a fixed quantity based on historical data. The net demand is calculated by subtracting the stock and the order stock from the gross demand and adding the reservations and the safety stock.

Gross / net calculation

  LagerbestandSicherheitsbestand (=Mindestreserve)
− Reservierungen (aus anderem Bedarf)
+ Bestellungen (mit Anlieferung zur Periode)
--------------------------------------------
= verfügbarer Lagerbestand
  Brutto-Sekundär-/Tertiärbedarf
+ Zusatzbedarf/Fehlmengenzuschlag
---------------------------------
= Brutto-Gesamtbedarf
− verfügbarer Lagerbestand
--------------------------------
= Netto-Sekundär-/Tertiärbedarf

If the net demand is positive, this means that material must be procured or manufactured to meet this demand. If the net demand is negative, this means that sufficient material is available and no order or production needs to be initiated.

It should be noted, however, that the calculation is theoretical, as safety stock is not used for every part and that the entire order stock is actually delivered or manufactured at the right time, in the right quantity and quality.

Decision alternatives

In the area of ​​the set decision there are no real alternatives , only between

  • Quantity takeoff and
  • Quantity determination

can be distinguished. In the case of the requirement quantity determination, no real decision is made by the materials management department, but the quantity determination is just a calculation that is determined by the production quantities. When determining the quantity, it is checked whether a reduction in the quantities to be procured or a time shift is possible. Measures for this can include lowering the level of service, should this be excessive, or lowering the reject rate through appropriate quality assurance.

Decision criteria

The manufacturing specifications are primarily used as decision criteria. A corresponding database of reject rates and times of need can serve as a decision criterion and as a support for determining the required quantity.

The ISAN is used to create material classes for which a different disposition effort is applied. A more precise and more intensive demand planning is carried out for the valuable A-goods. For this purpose, program-bound, deterministic methods of determining requirements are preferably used. For B-goods (less valuable, larger quantity), a consumption-oriented determination of needs using stochastic methods is more likely. The demand for C-goods is often estimated and thus carried out with little effort.

For example, quantity controls are carried out particularly precisely on A goods and less precisely on B and C goods according to their value proportions.

In the case of program- related processes, the quantity determination is derived from the production program or the production program with the help of parts lists or recipes (e.g. product tree , gozintograph , parts list ).

In the case of consumption-related processes (stochastic processes), the material requirement is determined on the basis of past consumption quantities. This method necessarily requires a suitable database on past consumption. Depending on the method, the most recent consumption values ​​are taken into account more or less. This takes account of a strongly or weakly fluctuating consumption curve. The aim is to get the most accurate forecast value possible for the next period.

In heuristic processes, the material requirement is determined using heuristics or on the basis of expert knowledge. The (subjective) experiences and estimates play an important role here. This method is useful if no historical values ​​are available or the independent requirement is not exactly known, as is the case e.g. B. is the case with completely new products. To support the market research, z. B. through dealer surveys. This method also plays an important role in very unstable market conditions.

Order point procedure

One of several methods of order quantity planning in which an order is always triggered when the stock level reaches or falls below a specified level (reorder level or order point). In the order point procedure with a fixed order quantity, a fixed quantity is ordered when the order inventory is reached. In the order point procedure with maximum stock, when the order point is reached, the quantity is ordered that replenishes the stock to the specified target stock. With both methods, the order times are variable, as they adapt to changes in the inventory issue.

Order rhythm procedure

Procedure for order quantity planning in which orders are placed in defined order rhythms. Either a fixed quantity is ordered at fixed time intervals (this leads to highly fluctuating stocks in the event of uneven stock removal) or the quantity that replenishes the stock to a fixed target stock is procured at fixed time intervals.

TARGET / ACTUAL procedure

This procedure is based on the control loop principle, in which the target values ​​and the actual values ​​are compared and the deviations are treated (regulated) in a specified manner in the MRP system. This process is (s. A., Especially in the cumulative needs assessment progress number principle ) is used, where the quantities required for each time section of a defined timeline are summed. The delivery or production quantity required at a point in time results from the difference between the cumulative target quantity and the cumulative actual quantity. For the calculation of a specific production or delivery order, lot sizes, quotas and capacity or delivery restrictions are also taken into account, whereby the call-off or order quantities are temporarily changed. The resulting increased delivery or production quantities then lead to increased ACTUAL quantities. Using the cumulative procedure and control cycle principle, the temporary differences are taken into account and cleared in the subsequent requirements calculation run. Since target values ​​are not yet available for the future, the planned target values ​​for one time unit are used as the actual values ​​for the next time unit, so that a target-actual calculation is also possible here.

The cumulative determination of requirements can be carried out for several successive recording points in the material flow (see also metering point ) and visualized with the aid of a cumulative figure diagram. The required amount of a detection point to the next detection point by means of the transit time brought forward. As a result, an extensive material flow of a part (see also the supply chain ) can be consistently calculated, planned and monitored, while at the same time a bullwhip effect is avoided, as all values ​​in the entire material flow of the value chain are linked.

For the TARGET-ACTUAL requirements determination, rolling planning is advantageous, in which the requirements are always determined for a fixed period of time and only the calendar is shifted when the planning period changes . The requirements are determined from a certain point in time (e.g. from the inventory), with a change of period the requirements from the past are condensed to the cumulative initial value, in which the results of the inventory flow as actual values.

In contrast to the gross-net requirement calculation, the stock level itself does not play a role in the cumulative determination of requirements, because 'only' the cumulative target is compared with the cumulative ACTUAL at the point of delivery of the warehouse . The inventory itself is a dynamic variable that results from the difference between the cumulative actual values ​​of the warehouse entry and exit, which can be influenced and regulated over the warehouse cycle time. If the specified warehouse throughput time is greater than the actual storage period, inventory is generated, but if the specified warehouse throughput time is shorter, the warehouse can “run empty” and material bottlenecks can arise. But the camp can also be "idle" or "overrun" when the desired values of the needs assessment does not agree, or if different from TARGET part is consumed or if the operating data is faulty. In contrast to the 'gross-net invoice', the 'TARGET / ACTUAL invoice' does not compensate for these errors. In order to detect errors or deviations, reporting limits (e.g. max-min stock) are therefore defined for the warehouse, which are compared with the actually ascertained warehouse stock; if these limits are violated, a warning is issued ("Alert" function). It must then be checked what the reason for the warning is and what is the reason for it (recording errors, deviating production / delivery quantities, incorrect parts list resolutions, changed production program ...) and how to react to it.

See also

literature

  • Oskar Grün: Industrial materials management. In: Marcell Schweitzer (Ed.): Industriebetriebslehre. 2nd Edition. Munich 1994, ISBN 3-8006-1755-2 , pp. 447-568.
  • Paul Schönsleben: Integral logistics management. 3. Edition. Springer-Verlag, Berlin 2002, ISBN 3-540-42655-8 .
  • Hans-Otto Günther, Horst Tempelmeier: Production and Logistics. 6th edition. Springer-Verlag, Berlin 2005, ISBN 3-540-23246-X .
  • Karl Kurb : Production planning and control. Methodological basics of PPS systems and extensions. 5th edition. Munich 2003, ISBN 3-486-27299-3 .
  • Michael Schenk, Rico Wojanowski: Progress figures . In: Reinhard Koether: Taschenbuch der Logistik. 2nd Edition. Fachbuchverlag Leipzig, Munich 2006, ISBN 3-446-40670-0 .
  • W. Herlyn: PPS in automobile construction - production program planning and control of vehicles and assemblies . Hanser Verlag, Munich 2012, ISBN 978-3-446-41370-2 .
  • W. Herlyn: The Bullwhip Effect in expanded Supply Chains and the Concept of Cumulative Quantities . epubli, Berlin 2014, ISBN 978-3-8442-9878-9 , pp. 513-528 .
  • Hans-Peter Wiendahl: Production control. Carl Hanser Verlag, Munich / Vienna 1997, ISBN 3-446-19084-8 .
  • Hans-Peter Wiendahl: Business organization for engineers . 6th edition. Hanser, Munich 2008, ISBN 978-3-446-41279-8 .
  • W. Herlyn: On the problem of mapping products with many variants in the automotive industry. VDI-Verlag, Düsseldorf 1990, ISBN 3-18-145216-5 .
  • Günther Schuh (Ed.): Production planning and control: Basics, design and concepts . 3. Edition. Springer, Berlin 2006, ISBN 3-540-40306-X .

Web links

Individual evidence

  1. ^ Winfried Krieger: Gabler Wirtschaftslexikon. Band: AB. 18th edition. Springer Gabler, Wiesbaden 2014, p. 364.
  2. ^ W. Herlyn: PPS in automobile construction. Hanser Verlag, Munich 2012, pp. 145–172.
  3. W. Herlyn: On the problem of mapping products with many variants in the automotive industry. VDI Verlag, Düsseldorf 1990, p. 99 ff.
  4. ^ A b Winfried Krieger: Gabler Wirtschaftslexikon. Band: AB. 18th edition. Springer Gabler, Wiesbaden 2014, p. 433.
  5. HP Wiendahl: Production control. Hanser Verlag, Berlin 1997, p. 344 ff.
  6. M. Schenk, R. Wojanowski: progress figures . Hanser Verlag, Munich 2006, p. 99 ff.
  7. ^ W. Herlyn: The Bullwhip Effect in expanded Supply Chains and the Concept of Cumulative Quantities. epubli Verlag, Berlin 2014, ISBN 978-3-8442-9878-9 , pp. 513-528.
  8. M. Schenk, R. Wojanowski: progress figures . In: R. Koether (Hrsg.): Taschenbuch der Logistik. Fachbuchverlag Leipzig, Munich 2006, ISBN 3-446-42512-8 , p. 104 ff.