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Former Member
Apr 13, 2016 at 01:54 PM

Lot Size Calculation


Hello All,

I'm beginning to use the optimal lot size setting "SP" (part-period balancing) on a select list of materials. I loaded the prerequisites on the material master, and ran MRP but the results are not as expected. I'm seeking your help to understand why my external calculations are not the same as SAPs planning with "SP" lot size. Below is the scenario:

Ordering Costs: $2,829.14

Storage Costs: 10%

Standard Price: $97.59


8/19/2016 - 185pc

9/23/2016 - 148pc

10/21/2016 - 165pc

11/23/2016 - 151pc

1/6/2017 - 136pc

2/3/2017 - 154pc
3/3/2017 - 147pc

3/31/2017 - 184pc
5/5/2017 - 182pc

6/9/2017 - 182pc

7/14/2017 - 143pc

8/11/2017 - 55pc

Problem: I was expecting the first supply element to be 1086 pieces, covering demand thru 3/3/2017, but MRP planned 333 pieces, only covering demand thru 9/23/2016.

My understanding is "SP" will continue to add requirements until the storage cost equals the ordering cost. With such expensive ordering costs, the storage cost will not intersect until 3/3/2017.

Any support is appreciated,