Friday is already sold
A manufacturer’s production manager sees eight unused machine hours and wants to accept a repeat batch. Idle capacity looks like wasted money. But the same machine must finish a custom order for a paying customer by Friday. Filling its calendar could make that promise expensive.
Two schedules, one correction
Consider one hypothetical week; every value is assumed. The machine has 40 regular hours, with 32 committed to the custom order. The repeat batch needs eight hours and offers €300 contribution after normal variable costs, before fixed costs. Its customer also accepts a confirmed slot next week. Four overtime hours are available at an all-in incremental cost of €90 per hour.
Now assume inspection reveals a defect requiring four machine hours of correction. The repeat run cannot pause without scrapping it.
Accepting the repeat batch uses 32 + 8 + 4 = 44 hours. Overtime keeps Friday’s delivery feasible, but costs 4 × €90 = €360. The batch’s incremental contribution becomes €300 − €360 = −€60.
Deferring it uses 32 + 4 = 36 hours, leaving four regular hours free. This option adds €0 from the repeat batch this week and incurs no overtime. Choose the later slot.
Reserve time where work returns
Idle hours act like a reservation for corrections. Once a continuous repeat run occupies the machine, those hours cannot absorb returning work.
Before booking, check the custom job’s inspection status and remaining machine hours. Count setup time and retain the four-hour correction allowance while inspection is open. Add the repeat run and compare with the week’s 40 available regular hours. If the total exceeds capacity, require confirmed overtime and contribution greater than its incremental cost; otherwise defer the repeat batch.
When filling the calendar fits
Change the example: inspection is complete and no correction remains. Then 32 + 8 = 40 hours, with €300 extra contribution and no overtime. Accept the repeat batch. Reserve capacity for identified uncertainty, not by habit.