Dear,
If you exclude the stock of SFG from MRP it will build the inventory stock for SFG products.Which you have to consume some where, or need sale it out. Other wise you will have unwanted inventory for these products which is nor right business practice.
For your requirement please try this,
FG maintain strategy as 11 with Mixed MRP Indicator in material master
SGF without any strategy with different storage location than FG and excluded the storage location from MRP through MMSC or material master setting. Same for raw materials too. So that system won;t consider the stock while running MRP and system will create a procurement proposal same as dependent requirement qty.
Please test the same and come back.
Regards,
R.Brahmankar