Order BOMs in MRP 
Use
MRP ensures that materials are available, which means that the required quantities are procured in due time.
MRP for order BOMs is basically the same as standard MRP. Merely the following prerequisites must be met.
Note
You can use the Project System for MRP. See Advance Procurement and Material Requirements Planning in BOM Transfer for further information.
Prerequisites
You have activated BOM explosion for sales order BOMs in the "Define BOM Explosion Control" activity in Customizing for MRP.
You have released the requirements for MRP (see also: Blocking Requirements ).
You have selected a strategy group in the material master that allows make-to-order production for the material in the sales order item.
You have set the Individual/coll. indicator to Individual and collective requirements or Individual requirements only in the material master ( MRP 4 view) for each header material in an order BOM. You have made the same settings for all assemblies that are on a higher level on a direct path above the order BOM.
Caution
The system always selects the material BOM in MRP when only collective requirements are allowed for an assembly. The material BOM is also selected when only collective requirements are allowed for an assembly that is on a higher level on a direct path.
You can use the explosion types ( basic data tab page on the item detail screen) in the BOM to override the setting in the material master record ( MRP 4 view).
Select an explosion type that allows either collective and individual requirements or individual requirements only on the item detail screen for the components in the higher-level BOM when you want to fix the BOM for a material and the setting for the BOM is collective requirements only . The setting in the BOM item overrides the setting in the material master record.
Features
There is an MRP run for make-to-order production. This planning run does the following with reference to the sales order item:
It determines the net requirements
It calculates the procurement quantities
It determines dates
It determines procurement elements
It explodes the multi-level BOM for the sales order item
You can check the planning result in the MRP list or the stock/requirements list.
A special case is when you work with detached order assemblies that you want to plan and manufacture before they are integrated in a multi-level BOM for a sales order item.
For further information on MRP, see PP – Material Requirements Planning , under
Control Parameters for the Planning Run