Hello,
We’re trying to understand the expected behavior behind how and why start dates change during job creation by MRP and release/schedule.
MRP often generates unfirmed jobs with very early start dates. However, when we go into Job Entry and release/schedule those jobs, the start date moves forward. We’d like to understand why this shift occurs and whether it’s expected system logic or a setup issue.
A related point: most of our jobs have one finite-scheduled operation. When we manually check the Finite Capacity checkbox on a job that already has a finite operation, the start date does not change when we release the job. Should we be checking that box when releasing jobs? If so, when is it appropriate, and if not, why does checking it lock the dates?
It seems likely that this behavior could be affecting our overall schedule, so we want to be sure we understand:
• Why MRP assigns an earlier start date to unfirmed jobs
• Why the start date shifts forward when releasing and scheduling through Job Entry
• Why checking the Finite box prevents the date change
• What the intended or correct workflow is to avoid unintended schedule changes
Any clarification on the expected logic and recommended process would be really helpful.
Typically when we release a job, we are using these standard selections –
When using these selections, you can see here that the unfirmed job has a start date of 12-17 but then when released, it changed to 2-13 when releasing with the scheduling above.
A theory : maybe MRP is running with finite scheduling and you are manually scheduling firm jobs with infinite scheduling.
On the screenshot of your unfirm job, it looks like the job was scheduled forward with finite scheduling, with a very early start date and a big gap between start and due date.
On the screenshot of your firm job, it looks like it was scheduled infinitely backward, hence a start and due date very close to the req date
It may have to do with allowing historical dates in the MRP run. I believe that will allow scheduling a start date prior to today to allow the job to finish on time.
The job scheduling may not allow historical dates (not sure) so it would have to start from today and go forward giving later dates
When looking at the images in your first post, I noticed that the Scheduling Options are for Job M1681570 and the Job Entry screen (after scheduled) is for Job M1681572. Is Job M1681570 for the same part? The only reason I ask is because that job was being scheduled Backward and the Due Date is showing as 12/17/2025, which is start date showing on the unfirm job.
What is causing the demand? Is it a sales order? If so, are there multiple releases on the sales order line with different Ship By Dates for each release?
I’m guessing that all the answers to those questions are yes which may play into the Start Date on the unfirm job.
