Find the True Constraint in Your Route
Do not assume the constraint is the most expensive machine. Look at queue times by work center over several months. In many gear shops the gear grinder carries the longest queue because of long setups and a single machine per accuracy class.
In others, outside heat treat adds 5 to 15 working days per pass, or the CMM and gear checker back up and hold finished parts. Shops with many part numbers and small lots lose capacity to setup and wheel dressing. Measure actual queue and run time from the ERP before deciding where to schedule finitely.
Finite Scheduling Where It Matters
Infinite-capacity MRP gives due dates that ignore real machine loads. For gear work, schedule finitely at least the constraint operations: gear cutting, grinding and inspection. Sequence jobs to reduce changeovers by grouping the same module, hob or wheel when due dates allow, and protect the grinder from starvation by keeping a buffer of hardened parts ahead of it.
Include machine capability in the rules: not every hobber cuts every diameter, and not every grinder handles internals or large helical gears.
- Machine capability (diameter, module, helix) as a scheduling constraint
- Setup grouping by hob, wheel and fixture
- Buffer ahead of the grinder and the inspection station
- Promise dates built from actual queue, not standard lead time
Outside Heat Treat and Other Vendor Steps
Heat treat vendors batch loads, so your parts wait for a full furnace, and a rush surcharge does not always move the date. Record the actual turnaround per vendor and process (carburize, induction, nitride, stress relief) and use that, not the quoted number, in your schedule. Consider consolidating loads of similar steel and case depth, and plan for rework passes.
Add transit time and receiving inspection of hardness and case depth certs. If a job needs a re-run because of distortion, the schedule should show the added cycle so sales can update the customer.
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Planned Order Offset and Start Date Calculator
Add setup, run, queue, move and safety time to get the lead time offset MRP should use to back schedule a made-in-house order.
Tooling, Fixtures and Programs
A gear job can be ready on paper and still be blocked by a missing hob, a worn grinding wheel, a fixture at another machine or a program not yet proven. Make tooling readiness part of release: confirm hob and wheel availability, dresser life, arbors and fixtures before the job reaches the machine. Special hobs for non-standard profiles have long lead times and should be flagged at quote time.
Track tool location and remaining life where it affects the schedule.
Using AI on Scheduling Questions
A private AI layer over the ERP can answer planner questions quickly: which open jobs depend on the grinder this month, how late has heat treat run on the last twenty lots, which part families have the longest setup. It can also draft a promise date from actual queues for a planner to confirm. It will not replace a finite scheduler or good routing data.
If your problem is that hours are not booked or routings are stale, fix those first; AI cannot schedule well on data nobody trusts.
Frequently asked questions
What is the usual bottleneck in a gear shop?
It depends on the mix. Often it is the gear grinder or the outside heat treat queue, sometimes the inspection station or a single hobber for certain sizes. Measure queue time by work center in your ERP over several months before choosing where to apply finite scheduling.
How do you quote lead times for gears with outside heat treat?
Add the actual recent turnaround of your heat treat vendor, plus transit and receiving inspection, to the internal queue before and after. Use real history, include a buffer for rework passes, and update the promise date when the part ships out for heat treat.
Do we need APS software for a gear job shop?
Not always. Many shops get most of the benefit from finite scheduling on two or three constraint work centers inside the ERP or a lighter scheduling tool. Consider APS when mix, volume and multi-plant routing make manual sequencing too slow.
Ask Netray to show queue time, heat treat turnaround and setup history by work center straight from your ERP, with the query visible.