Difference between MRP Type PD and VB

Depending on this field , the behaviour of MRP will be completely different.When you work with PD, you work with BOM structures.

Imagine the final material A , and its component B you need 2 pieces of B to produce 1 piece of A.If you work with PD and you receive for example a sales order for A of 10 pieces , the MRP with PD will determinate that you need 20 pieces of B taken into account the sales order delivery date. The system will use the BOM to know the quantity that you need. You will not have additional stock for the component B. The system will procure when and how many pieces you need.

IF with the same example you work with VB for component B, then you have to define a reorder point (example 5).

If your stock is bellow that level ,the system will procure to get again the reorder point level. If you have enough stock (example 30) the system will not create any purchase requisiton for B, independent of the sales orders of A , and the reservation of 20 pieces.

When yuo work with expensive components you should use PD , because you don´t have stock without pegged requirements. if the materials are cheap and you need to have allways some stock , you can define VB as planning type.IF you use ND. the component B will not be planned, that means the MRP will not create any planned order or purchase requisition to cover requirements. you have to create manually.