We have been looking at the results from MRP, and it seems the Days of Supply in Epicor 10.2.700.26 is looking at raw calendar days, including the weekends, to pull in future demand. I made sure the supplier has a calendar assigned (8x5 - 5 days 8 hours), and our production calendar for the site is also assigned (same calendar)
When I searched the forum posts, they all seemed to indicate it is supposed to use the Supplier Calendar, then the Production calendar to calculate how far in the future to pull demand in.
I can provide a sample of the issue if it helps, but I wanted to first see if I am way off base in my thinking.
The MRP Technical Reference manual for 10.2.700 does NOT specify that the Days of Supply calculation involves any calendar at all (page 148-149). The Calendar entry only specifies that the MRP engine only uses Supplier calendars for arrival of materials or subcontract operations (page 40).
I had also always assumed it used the Supplier calendar… but never tested it.
MRP Tech Ref for 2023.2 has exactly the same verbiage for Days of Supply and Calendar, so no change in a newer version.
I agree. This setting is strictly used for calculating total demand, supply has nothing to do with this setting, so a supplier calendar would not have any bearing here.
Days of supply (DOS) does not use any calendar and will count weekends and holidays. It is not normally something that is to be that “finite” in the planning… Most companies use it to plan for 1 day, 7 days, 30 days, 90 days… having a DOS of 3 could lead to misleading suggestions since a 3 day DOS on a Friday would only look at Friday, Saturday and Sunday.
DOS is intended to bucketize your suggestions into bigger buckets to reduce the “noise” of suggestions.
Here is an example of how various days of supply can have an effect on purchasing (or jobs). While this is not 100% accurate is is very close (This does not show what happens if there is zero demand on a day mid week). Note that I typically like to use a DOS that is an increment of 7, so that you only get one suggestion per WEEK, and you take weekly deliveries. one reason is that if you choose something like 3 or 5, it eventually causes all recommendations to synchronize to Mondays because DOS will not suggest a demand on a Saturday or Sunday. You can see this in this example, as the first recommendation is on a Wednesday for 3 and 5 DOS, but the next syncs to Monday… the 3 DOS turns into ordering every Monday and Thursday. 7 and 14 DOS syncs to Wednesdays because that is when the first demand is. 28 DOS (an increment of 7) syncs to Wednesdays, but 31 DOS falls onto a Saturday, so it moves to a Monday again… I don’t like to cause bubbles of suggestions on Mondays (or the day after a holiday) which is why I always suggest DOS increment of 7.
Interesting. I noticed or thought about this. Though, our days of supply are around 90 days (or more for long lead items) to maximize economies of scale.
So, you might consider making DOS either 91 (13 full weeks) or 84 days (12 weeks)… although it probably doesn’t matter in those cases, because the DOS calculation also starts with the first demand after the 90 days… so unless you have daily demands, you may not get to that Monday synchronization that I mentioned before.
