As I originally understood it, A buy direct part is supposed to constrain that material, which in turn should push a related operations start date if that part is not due in until after the original start date, correct?
I think that sorta works, but I get mixed results.
I have many jobs that cannot start at all without 1 Material, so I mark that material as buy direct to hopefully constrain the job to reschedule after that materials due date (which i assume would ultimately come from the PO that Material is on). On many jobs, it seems to help to reschedule the start date , But every now and again, it seems like it will allow the job to start 20-30 days earlier then the constrained material is supposed to arrive. (long lead time part). We do not have the module to define constrained materials, BUT i though Buy direct materials were supposed to do that anyway.
Am i missing a setup function somewhere? I feel this may have something to do with horizons or deltas, but they are part of my part classes.
Or is this not actually going to work the way I think.
I want to simply adjust the due date on the po release to reflect actual incoming time and have that affect the job schedule with an MRP run and Global reschedule…
The only way I’ve been able to make constraint work is through the addition of the advanced planning and scheduling module. It’s a challenging process even then, but it does work. Constraint is enabled on the part entry screen.
I think I just found my issue, and maybe it would help others with the same problem.
It looks like what happens is the job will follow the original lead time on the buy direct part, NOT the po due date, if the po due date is Greater than the lead time. To fix it, I just put in the lead time on the job at 360 days (after that parts po was written and dated), and the job rescheduled to be after the PO due date, but at the earliest scheduled time. Basically not giving a rip about the 360 days, but caring about that buy direct due time.
So it seems to follow this Logic:
Lead time < PO Due date - Follow Lead time for scheduling
Lead Time > Po Due Date - Follow Po date.
I am sure something else will pop up trying to do this, but for now it is working exactly as I need.
That’s a very interesting result. I would test that a couple of more times to make sure it works on a few different items before embedding your logic into your brain permanently.
I tested it on 144 jobs with this problem and totally solved it.
main issue I see is if we put that part in the part master with a non-stock and 360 day lead, it will originally push jobs to be out 360 days plus which is simply not true. I can resolve this with process, but it will definitely cause problems someday.
That is because MRP will use lead time as the determining factor when you don’t have material on hand (or already on order). If you need it now, and the lead time is 300 days, it will tell you to bring it in 300 days from now.
One of the workarounds we use for this is to rerun generate purchase suggestions after our MRP runs, and allow historical dates. By doing that, it will tell us when we “should have” ordered something, and will also tell us what day we actually need it, instead of saying we “need it 300 days from now” because that’s the lead time.
fortunately, It is only ever 1 part, and we regen schedules all the time. My main concern would actually be trying to use the what if schedule to tell a customer their anticipated build date.