A shop that makes excellent prototypes and a shop that supplies production parts month after month are different businesses with different equipment, different economics and different failure modes. Buying production volume from a jobbing shop, or prototypes from a production supplier, is a common and expensive mismatch.
What production machining is set up for
Dedicated fixtures rather than vices, bar feeders and pallet systems for unattended running, in process gauging, and programmes that have been optimised rather than merely proven. The result is a low cost per part and a high cost per change. A jobbing shop is the reverse, and both are correct for what they do.
Process control and what it means in practice
Documented setup sheets so any operator produces the same part. Tool life management so a worn tool is changed on schedule rather than when a part fails. In process inspection with recorded results. Change control so nobody quietly substitutes a tool or a supplier. Ask to see these rather than asking whether they exist.
Inspection and first articles
A first article inspection report against every dimension on the drawing is the normal entry point for a production part, and it is worth reading rather than filing. Agree the ongoing inspection regime: what is measured, how often, and what happens when something drifts. Agree what a nonconformance looks like and who decides.
The commercial arrangement
Agree the price at a stated annual volume and the mechanism for material price changes. Agree lead time and the order horizon. Agree who owns fixtures and programmes. Agree how engineering changes are quoted and implemented. And agree what stock, if any, either side holds, because that is where continuity of supply actually lives.
Questions people ask about cnc machining parts manufacturer
What is the difference between a jobbing shop and a production supplier?
A jobbing shop is optimised for change and a production supplier for repetition. Fixtures, automation, process control and cost per part all differ accordingly.
What should a first article inspection report cover?
Every dimension on the drawing, measured on a part from the production setup, with the equipment identified. It is the baseline every later part is compared against.
Who owns the fixtures and programmes?
Whatever the agreement says. If you paid for a dedicated fixture, say in writing that you own it and can have it back, or moving the work later becomes a new tooling exercise.
How should engineering changes be handled?
Through a defined route: the supplier quotes the change, both sides agree the effective date, and stock made to the old revision is dispositioned explicitly.