When I use follow-up material , I meet a trouble.
There are 2 materials, Rmat_old and Rmat_new. We hope to use Rmat_new to replace Rmat_old, but Rmat_old has some stocks and also has open PO. So we set Rmat_new as the follow-up material of Rmat_old (in material mast, MRP View 4 => Discontin.ind. = 1, Eff.-out = ‘’, Follow-up mat. = Rmat_new). For example, Rmat_old stock = 100, Rmat_old open PO = 80(delivery date = 20131015). When we have a new dependent requirement 500, we hope MRP suggest us that Rmat_old plan order = 0 and Rmat_new plan order = 320. In fact, in the scene Rmat_new = 400. MRP just consider the stock but no open PO. Then we change Eff.-out = 20131016, this time the result is right: Rmat_new = 320.
I don’t know why SAP just consider the stock but no open PO, generally speaking, open PO is the fix supply of a company. Maybe I can set the Eff.-out date to avoid excess plan qty. But the fact is that sometimes we will change open PO’s delivery date! If purchasing department just change the PO’s delivery date as 20131115, the MRP result will error! How to deal with it? If we want to consider the open PO of old material , we must enhance MRP program? Where to enhance? Thanks very much.