A prototype and a production order for the same machined part are not specified the same way, and treating the prototype drawing as production-ready is one of the more common ways a quote comes back wrong or a part fails a fit check it should have passed. The design question changes from "does this work" to "can this be built the same way every time" -- and that changes what belongs on the drawing and in the RFQ.

What a prototype does not have to answer yet

A rapid prototype is built to settle one question fast, not to anticipate a production run. Process selection during prototyping is driven by what the build needs to prove -- geometry, function or material behavior -- and the part is often evaluated in a stand-in material like SLA resin or SLS nylon rather than the final specified alloy or engineering plastic. Tolerances are usually general, secondary operations are often skipped, and the drawing may not yet call out which features are actually critical to fit or function. None of that is a shortcut being taken; it is appropriate for what the prototype is being asked to answer.

What tightens once the part becomes a production order

Once a design is heading into CNC machining for a production run, three things usually need to be revisited. Material moves from a stand-in to the specified condition -- titanium, stainless steel, cobalt-chrome, aluminum, tool steel or an engineering plastic such as PEEK, PPSU, PEI or POM, matched to what the application actually requires. Tolerances get concentrated on the features that decide fit and function -- mating surfaces, bearing points and alignment features -- rather than tightened uniformly across the part, since uniform tightening adds cost without adding value on non-critical geometry. And secondary operations a prototype skipped, such as threading, drilling, knurling, boring, EDM, grinding, deburring or passivation, need to be called out explicitly if the production part requires them.

What the RFQ needs that the prototype request did not

A prototype RFQ and a production RFQ ask for different information because they are answering different questions. A production RFQ needs the final material, the critical tolerances -- not just overall dimensions -- the specified finish, any inspection or fit-check requirements and a real target quantity. Quantity itself is worth revisiting rather than assuming it carries over from the prototype stage -- the right route for one-off versus small-batch production depends on design stability and follow-on volume, not just how many units the prototype run used.

Fit still has to be re-checked, not assumed

A fit check that passed on a prototype does not automatically carry over once material or tolerances change -- a resin or nylon prototype can behave differently under load, thermal expansion or surface friction than the production alloy. Trial fit and assembly checks on the production-representative part are what actually confirm a design is ready to sign off, not the earlier prototype fit.

Send the updated drawing along with a note on which features are now critical to fit or function, the specified material and the expected quantity -- through the RFQ checklist or directly to Lab Ready -- and the quote will reflect the production requirement instead of the prototype it started as.