Material Requirements Planning: Long-Term/Short-Term Lot Size
Description
The long-term lot size is used to split up the time axis for material requirements planning into a short-term and a long-term area. In these two areas, it is possible to carry out the lot-size calculation using two different lot-sizing procedures.
This procedure means that is is possible, for example, to group together requirements over a larger period in the long-term area simply to produce a rough picture of the future master plan. In the short-term area, however, you can select a smaller, more precise lot size to suit your requirements.
Steps to take
In the planning run, if a material is planned with a short and a long-term lot size, the system calculates the time axis for the validity of both lot-sizing procedures. The order quantities in the first, short-term area are calculated using the short-term lot size. From the 'valid from' date of the long-term lot size the system switches to the long-term lot size.
If no long-term lot size has been specified for a lot-sizing procedure, the system plans the complete planning period using the short-term lot size.
Change system parameters in customizing
The settings for the long-term lot size are maintained in Customizing for MRP in the step, "Check lot-sizing procedure".
You must specify a lot-sizing procedure for the short-term period as well as for the long-term period.
The same control parameters are available for the lot size in the long-term period and for the lot size in the short-term period.
It is possible to select any lot-sizing procedure for the long-term lot size, however, it makes most sense to select a period lot-sizing procedure. Thus, you can roughly group requirements together in the more distant future.
You can also specify whether the system is to take account of the lot-sizing parameters, 'maximum lot size' and the 'minimum lot size' in the lot-size calculation for the long-term period. These parameters are maintained in the material master record.
Validity of the long-term lot size
The start of the validity of the long-term lot size is determined due to the number of periods specified. To calculate the valid from date, the system always rounds up to the end of a period that has already started and then sets the valid from date to the beginning of the next complete period.
Example
The calculation of the valid from date for the long-term lot size starts on the 15th March. Four months have been entered for the periods for this calculation. The system then calculates four months into the future (15 July) and then rounds up to the beginning of the next complete period. This means that the long-term lot size is valid from the 1st August.
Please read the chapter in the Implementation Guide:
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