Use Finite capacity in Master Planning
Dynamics AX allows finite capacity scheduling during Master Planning. This is not a feature a discrete manufacturing company would ever use for its regular MRP-runs. But the traditional ‘RCCP’, Rough-Cut Capacity Planning, is still alive and well in the world of Sales and Operations planning. If I make plans for next year, I need to know if my facility is able to handle the volumes and/or product mixes that the operational plan is talking about.
I would create a special Master Plan, call it “long term capacity view” or similar, and use it to see expected capacity loads on my resources up to a year ahead, using forecasts provided by sales.
I have to make sure the “capacity time fence” is equal to the coverage time fence. (which we typically do anyway)
Since computers have become powerful enough to explode actual routings during the MRP run, there is no such thing as a “rough-cut” functionality anymore. We could use simplified routings if the detailed routings are not known in the case of configured products.
Use Finite capacity in weekly operation or job scheduling
The common practice in discrete manufacturing industries is a regular MRP run, (at least weekly) infinite capacity. Then for the short term, we run Operation or Job Scheduling with finite capacity.
There are a few important points to keep in mind.
(1) With infinite capacity scheduling, it makes no difference whether I schedule one Production order at a time or a bunch of them together. The results are identical. With finite capacity scheduling, it makes all the difference. Production orders will be “competing” for available hours on resources. Who gets the hours first?
(2) The key word is “sorting”. If I highlight a number of production orders that I want to schedule together (for example next week’s production schedule) and I don’t do anything to sort them, the production order with the lowest order number gets the first chance to reserve hours.
(3) In Dynamics AX there are four sorting options: (click “SORTING” button once in the Operation or Job scheduling screen)
Ascending Item level, delivery date
Descending item level, delivery date
Status, scheduled start
Priority, delivery date
Each sort choice has a primary and a secondary sort.
The first two choices “Ascending item level, delivery date”, “Descending item level, delivery date” imply that I would schedule lower level items (items on lower BOM levels) first.
That means I would schedule finished products with higher priority then subassemblies. There may be a use for this, but I have not found it so far. The second option would turn that around, I would schedule subassemblies first, finished products next. That would make some logical sense. If subassemblies and finished products compete for the same resources, the subassemblies should go first.
The sorting on item level uses the field “BOM-level” in the Inventtable. (which is the Low Level code in the Apics dictionary).
The third choice “Status – scheduled start date”, uses a sort by production order status which can be of use if I am rescheduling already started production orders and would give them priority.
But I don’t see much use in using production order -status otherwise. Production orders go from estimated to scheduled after I have run a finite scheduling job. Then I release them and the Manufacturing execution functionality will start them. There is no meaningful set of statuses that I would use to prioritize my orders for a scheduling run. So the third option is not a practical choice for weekly or daily (re) scheduling either.
The fourth option is instantly clear and very usable. I sort by priority and for orders with the same priority, the sort is by delivery date.
If I do not use priorities, this is still the correct choice as the system will schedule early delivery dates first.
CONCLUSION
Sorting is all important! Because other then the sort sequence, there is no other way to influence finite capacity scheduling logic. Production orders do not really compete, they just get sorted by the user (always manually) and capacity is reserved in strict order sequence.
Procedurally, (not system enforced) sorting SHOULD BE A MANDATORY STEP. It is only available when I use the scheduling functionality in the Periodic section of the menu.