Finite vs. infinite capacity
Most ERP and MRP systems plan assuming infinite capacity: they compute when each order should start, but never check whether the machines are free. The result is dates that don’t hold and queues nobody foresaw. Finite-capacity planning builds a realistic sequence where each machine runs one operation at a time, with its calendars, shifts and stoppages.
Flexible job-shop scheduling
The model that best fits a make-to-order shop is a flexible job-shop scheduling problem:
- Each order has several operations with precedences.
- Each operation can run on one or several compatible machines.
- Machines have calendars, shifts and stoppages.
- Some sequences require setup changes.
- Some operations have already started and can’t move.
The right objective isn’t makespan
Academic examples minimize total time (makespan). In a real factory the useful objective combines weighted tardiness, setup changes, overtime and stability. Priority order: first a feasible plan; then fewer late deliveries; then fewer setups and overtime; and last, don’t touch the previous plan without reason.
FAQ
Is this an APS?
It’s a lightweight copilot focused on finite capacity and rescheduling. It covers the real problem of a make-to-order shop without the complexity or cost of rolling out a full APS.
What data do I need?
Orders, operations and routings, compatible machines, calendars and shifts, changeover times and execution status. You can start with what you already have in Excel or CSV.