We are actually using the MRP types PD/P1 and SAP is calculating our suppliers deliveries in a correct way.
The problem occurs when we schedule our production based on the next 8 weeks requirements in order to get a weekly average quantity to produce per week that can handle the future peaks and valleys and avoid over-time or iddleness in the production line.
The MRP plans the arrival of components according to the future weeks demand, considering safety time, safety stocks, transit time, etc. and most important considering peaks and valleys. Because of this we have run out of material some days. Our MRP is doing the calculations in a correct mathematical logic.
What we want is to find maybe a type of MRP that can make the same that we're doing in the production scheduling: consider the next 8 weeks of consumption, determine the average and put it as open order in the delivery schedules. This has to take effect only in the purchased items, we need to keep our Customer's orders as they arrive to our system obviously.
Probably the adjustments must be done in the Production scheduling proposals that the MRP generates?