I am curious on whether our MRP is setup/running correctly. We had a strange result that I would like to outline and see if MRP may have an issue.
For example, take a three-level part. Each level only takes 1 day to complete and only requires a qty of 1 to produce the next level. In addition, let’s assume all parts are make items. Part C is made from part B. Part B is made from part A. Thus, the BOM looks like:
1 Asm C
2 Asm B
3 Asm A
I have always assumed MRP planned from the bottom up. Meaning if a customer orders 100 parts of Part C, MRP production jobs will automatically be triggered starting at level A. On the first day MRP will tell us to produce 100 parts of item A. On day 2 we will need to produce a 100 parts of item B (consuming items A). On day 3 we will need to produce 100 parts of item C (consuming item B). Assume the customer gave us a 3-day window.
However, our MRP process worked from the top down. It told us to make a job for 100 parts of item C. Then it told us to make a 100 parts of part B. Lastly it told us to make 100 parts of part A. It would not tell us to work from the bottom up. In addition, even “Time Phased” did not display the requirements for item A until the other top levels where “firmed.” There was no on-hand quantity of the items. Seems very strange.
I realize this is a very basic example and MRP is/can be very complex. Nonetheless, is there a basic setting I am missing or has anyone else experienced this behavior and how was it solved?
@RWB you must have something incorrectly defined, because i can guarantee you that MRP plans correctly.
using your scenario of an item C that has a B, which as an A. also assuming that each item has a ONE DAY schedule to complete… I will also add the scenario that item C is due on Oct 30.
Create an order for C
MRP runs, and it should create three jobs.
Job 1 for part C should be scheduled at the end on Oct 30
Job 2 for part B should be scheduled to complete on Oct 29
Job 3 for part A should be scheduled to complete on Oct 28.
MRP will create all three jobs at once… but they will be in the job sequence described above.
NOTE that if you don’t have any operations, or if your operations have zero time, then all three jobs would be scheduled to complete on Oct 30.
We are backwards scheduling and “Pull as Assembly” & “Plan as Assembly” are both unchecked.
Tim, I agree with what you you stated. MRP would create 3 jobs at once for all three levels. However, in our case the job for item B was not suggested until we firmed item C. In addition, the job for item A was not suggested until we firmed B. Thus, the demand for both item B & A was hidden unless we started with item C even though item C is the last build. Does that make sense?
that does not make sense… have you looked at timephase display for item a, b, and c? MRP would not suggest making any C unless there was a demand from it (coming from B).
Also, do you have Constrained material set for items B & C?
I agree. C is made from B. B is made from A. We had a customer order come in ordering item C. I did not see any job (or demand in time phased) for B or A until I firmed the job for C. After I firmed the job for C, then MRP told me to make a job for B. I firmed B and then MRP told me to make a job for A. MRP had to “run” three times before I saw a job requirement for item A even though item A is the bottom (first level required).
No we do not have constrained material set for items B & C.
Sorry it has taken me a bit to get back with a response. We were able to figure this out yesterday and it was tied to some inventory adjustments were entered coincidentally at the same time we were looking at the issues. We where unaware of the entries until we did a “deep” dive into the part(s) and found our inventory manager was doing some cycle counting at the same time we were troubleshooting.
Tim & John I appreciate the responses and assistance.