Calculate grinding costs from the tolerances that cause them.
Grinding is a finishing step a drawing forces. The cause is a fit, a finish or a flatness callout that milling or turning cannot hold. ARCNM reads those callouts and checks them against what each machine class can hold. It routes the affected surfaces to a surface or cylindrical grinder in your fleet. It prices them with setup and cycle time at the machine-hour rate, next to the machining that came before. A grinding segment on the routing always names the callout that caused it.
At a glance
- Inputs
- STEP model and PDF drawing with IT grade, geometric tolerance or roughness callouts
- Machine classes
- surface grinder · cylindrical grinder — one operation per ground surface
- Standards applied
- ISO 286 IT grades · ISO 1101 zones · ISO 21920 / ISO 1302 roughness · DIN 8580
- DfM checks
- every surface that needs grinding is named with the drawing callout that requires it
- You get
- a grinding operation per callout with its time and cost, placed in the routing after the machining
When does ARCNM add a grinding operation?
ARCNM adds grinding when a drawing callout is tighter than the machining class can hold. That callout can be a tolerance, a geometric tolerance or a surface finish. Dimensional tolerances are read per ISO 286 and ISO 2768. Geometric tolerances are read per ISO 1101, roughness per ISO 21920. The escalation is per surface. So a shaft with one ground bearing seat is not priced as a fully ground part.
What do you get for a ground part?
You get a grinding operation per surface, on the right machine. Surface grinding covers flat faces, cylindrical grinding covers shafts and bores. Each is its own machine class with its own rate. Every operation carries its setup and cycle time, its share of the unit cost and the callout that caused it. Your own grinding data takes over as soon as you enter it.
What makes ground parts expensive?
- The number of ground surfaces and their area — each one is its own operation.
- Grinding stock left by the previous operation, which sets the volume to remove.
- Hardened parts: the heat treatment is priced as a subcontract step. The machining before grinding is priced for the hardened material.
- Setup per surface orientation, amortised over the lot.
Which callout forces grinding?
| Callout on the drawing | Milled or turned | Ground | Typical feature |
|---|---|---|---|
| Dimensional tolerance (ISO 286) | standard and fine fits | very tight fits | bearing seats, gauge faces |
| Surface roughness | a good machined finish | a fine, smooth finish | seal faces, sliding surfaces |
| Geometric tolerance (ISO 1101) | standard flatness and cylindricity | very tight zones | datum faces, precision bores |
| Hardened material | before heat treatment | any finishing after hardening | shafts, dies, cams |
Read on
Frequently asked questions
Can I avoid grinding by changing the drawing?
Often. The routing shows which callout triggered grinding. Relax that tolerance or finish where the function allows. Re-run the calculation, and the grinding segment and its cost disappear from the result.
Does ARCNM price grinding on a hardened part?
Yes. Heat treatment from the drawing is added as a subcontract step. The machining of the hardened part is priced for the hardened material. So is the grinding after it.