Lot sizing procedure for Make-to-Order
When we are planning a material on an individual stock, such as a sales order stock or a WBS stock, this material is planned on a separate stock segment.
In this case, the existing replenishment elements and the plant stock are not considered by MRP to cover the requirements under this individual stock and new planned orders are created by MRP to cover those requirements.
By default, MRP will consider the standard lot-for-lot logic (similar to lot sizing procedure EX) and it will create replenishment elements to cover exactly the shortage quantity. This standard logic for individual planning was developed, in order to avoid a leftover stock under the individual segment, as it would need an additional goods movement to transfer this leftover from the individual stock to the plant stock.
Considering the example below, where a fixed lot sizing procedure (FX) of 10 was defined for the material. On the Stock/Requirements List (transaction MD04), we can clearly see that MRP created planned orders of 10 EA to cover the Planned Independent Requirements, respecting the lot sizing constraints.
However, for a sales order under the individual sales order stock, a single order planned order of 30 EA was created to cover the sales order requirement, which means that the fixed lot sizing procedure was not considered.
Under specific circumstances, we want to use a different lot sizing procedure under the individual stock, such as a fixed lot sizing procedure or a rounding value for example. In this case, there is a setting on the lot sizing procedure customizing which allows us to choose which logic we want to use under the individual stock segments.
The mentioned customizing can be found in transaction OMI4, as we can see in the image below:
The options available for this customizing setting allow us to simply consider the rounding or to use the same lot sizing procedure used in the Short-Term Horizon.
Now, let’s see what happens on the same example if we create a new lot sizing procedure, as a copy of the standard lot sizing procedure FX. Here, we will change the value of the field Lot Size: MtO to 2 – ‘Lot size as in short-term period’ and set this lot sizing procedure for the same material used on the previous example.
Here, we will observe that the same logic used to calculate the quantity of the planned orders created to cover the PIRs was used for the planned orders created under the individual stock. That means, the fixed lot size of 10 was considered under the individual stock.
Besides a sales order individual stock, the same setting is also valid for a project or WBS individual stock.