A prototype proves a part can be made. Repeat production proves it can be made the same way again. What bridges the two is not the part itself but the record: the approved drawing revision, the process route, the fixturing and the inspection results that showed it was right.
6 min read · Last reviewed 28 September 2026 · All resources
A first part is usually made with more attention and more manual intervention than a production part will receive. That is appropriate — but it means the result is not automatically repeatable.
What makes it repeatable is writing down what was actually done: the route, the fixturing, the order of operations, where material was left and what was measured. Without that, the second batch is a fresh experiment.
The drawing revision the prototype was made to is the only meaningful reference for what was approved. If the drawing moves afterwards without a new approval, the repeat order is being made to something nobody has signed off.
This sounds obvious and is the most common cause of disputes about repeat parts not matching the sample.
The prototype's inspection establishes what 'correct' means. For repeat production, decide which of those characteristics are checked every time, which are sampled, and what happens when one drifts.
That decision is worth making jointly. A supplier checking the wrong three dimensions thoroughly is no protection if the fourth is what actually controls assembly.
The first repeat run is where any dependence on the original operator, the original bar of material or the original machine reveals itself. It is normal for something small to surface.
The useful response is to update the record rather than to fix it informally. A route that only works because one person remembers a detail will fail the moment that person is elsewhere.
FAQ
The questions engineers and buyers ask before sending a drawing. If yours is not here, ask it directly — you will get an engineer's answer, not a brochure.
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Talk to Anita M.N, Managing Partner, or send the drawing and let the review answer it.
Where practical, yes — it removes one variable. Where it is not possible, the difference should be known, because a route proven on one machine does not automatically transfer.
Enough to see variation rather than a single result. A handful of parts, ideally across more than one setup, shows whether the process is stable or the first one was fortunate.
You should hold it, and so should the supplier. Ask explicitly — it is what allows a reorder years later to be made the same way.
Treat it as a new approval rather than an amendment in passing. A revised drawing, reviewed and accepted, avoids parts being made to two different intents at once.
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