Statistical Process Control for CNC Standard Work

Standard work for statistical process control for CNC: what belongs in a written procedure, a practical checklist structure, and how to keep documentation current rather than decorative.

Why write it down

A written procedure makes the best known method available to everyone on every shift, and it gives new starters a place to start instead of a guess.

Statistical Process Control for CNC is tracking measured dimensions over time to separate common cause from special cause variation, and the fewest surprises happen when every operator sets it up in the same documented way to achieve control charts that flag drift before parts leave tolerance.

What belongs in the document

Include material details, machine and tooling list, setup sequence, offsets and probing, inspection points, and the reaction to common problems.

Keep each step short and testable, because anything longer than one line gets skipped under production pressure.

Building the checklist

Split checks into before setup, before the first cut, during running and at handover, then keep the whole thing to one page.

A checklist that takes more than two minutes to complete will not survive its first busy week.

Revision discipline

Every process improvement changes the document, so keep revision numbers on the sheet itself and withdraw printed copies from the floor on update.

Old revisions in a drawer cause more problems than having no procedure at all.

Auditing that improves things

Audit monthly against one part family, ask the operator what the sheet gets wrong, and correct it in the same week.

Procedures improve fastest when the people using them are allowed to change them.

Summary

The value of statistical process control for CNC is easiest to see when the result is written down, measured and compared against the drawing.