Work Order Start Dates
When an item has a fixed lead time, the system uses the item's level lead time value to backschedule the work order start date. For backscheduling, the start of a work order is based on the due date of the order.
For example, suppose that the system generates a planned order with a requested due date of October 15. The level lead time is three days for this product, so the system calculates the start date by counting back three working days on the shop floor calendar from (but not including) the requested date. The system assigns the order a start date of October 12.
When an item has a variable lead time, the system uses this calculation to determine the lead time days:
(Lead time per unit × order quantity / TIMB*) + setup + total queue/move = Variable lead time
The system reads the time basis code (TIMB) from the Item Branch File table (F4102).
The calculation uses these values:
Due date: October 15.
Lead time per unit: 32 hours.
Order quantity: 1,000.
Setup: 1 hour.
Total queue/move: 9 hours.
Work hours per day: 8 hours.
((32 × 1000 / 10,000) + 1 + 9) / 8 = 2 days
To determine the start date, the system counts back the lead time days from the due date of planned orders. The system back schedules the due date, October 15, two days to determine the start date of October 13.