Study Material Contributed by Ulhas Kavle 

Last Step  <<< Determination of the type of Procurement Proposal – External or Internal Run 

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Step 10: 

BOM Explosion in a SAP MRP Run for Calculation of Dependent Requirements 

Once the procurement proposals are created, lot sized, and scheduled, the next step in the SAP MRP Algorithm is to explode the BOM for all the levels below the header level in question. Such kind of BOM explosion of all the levels below is only carried out in single item-multi level planning runs. 

This step is the last step in a SAP MRP Run. 

If the material that is being planned is an in-house manufactured material, then the system also plans all the dependent requirements as found in the bill of material of the assembly or the subassembly. 

To select a valid Bill of Material (BOM) for the in-house manufactured material, the system goes to the MRP 4 view of the material master and checks the selection method entered for the BOM Explosion: 

a)      If the selection method is based upon the proposal (order) quantity, it picks up a BOM whose defined lot sizes and date validities is within the order quantity proposed. 

b)      Whereas if the selection is based on explosion dates, it checks the BOM alternates and the validity of the alternates in the transaction code OPPP. 

c)      And if the selection is based on production versions, the system selects the production version according to the lot sizing and the validity dates included in the production versions. Eventually the BOM alternate and the task list included in the version is used for the MRP run. 

In the process of planning for the higher level manufactured material, the system explodes its Bill of Material (BOM) and identifies the components/sub-assemblies and their quantities required in the manufacturing. The system works on programmed concept called low level codes, wherein it explodes the highest level codes first thereby evaluating its requirement and then moves hierarchically downwards (into lower level codes) to calculate the quantities required for each of the component. SAP does this till it reaches the lower most level (and there is no level to explode further). The highest level material has a low level code of “000” while the next lower level component/sub-assembly would have a low level code of “001” so on and so forth.   

SAP treats each one of the exploded levels in the same way as it would treat the higher most level, thereby calculating the net requirement for these dependents, exploding their respective BOMS (if the component is an in-house manufactured material) and also  scheduling it in the same way. 

It should be noted that, it is not necessary to have SAP MRP successfully adjust/schedule the levels one after the other (in a hierarchical fashion) to carry out finite based planning. It is known fact that SAP MRP is not a finite based planning method and user intervention is a absolutely necessary. 

Below is the Ideal way of SAP MRP planning, where all the levels are scheduled to be processed one after the other and there is no parallel processing of the sub-assemblies unless you purposely wanted one.

You should not be surprised if SAP MRP comes up with the following planning situation between levels:

The above situation arises because SAP MRP does not believe in finite based planning and plans based on infinite based planning. It is expected that an MRP controller in charge of the material planning for the concerned material (as indicated in the material master MRP 1) is expected to carry out all the “re-scheduling” or adjusting so that the planning situation looks favorable, as below: 

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