How to Source Prototype Parts
Prototype RFQ checklist: what the prototype must prove, which features must match production, process and material choices, and fast-turn trade-offs.
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A prototype is a question in physical form: does it fit, does it work, does it survive, will customers want it. The right process and the right amount of precision depend on the question. A fit check can be printed overnight; a load test of a machined bracket should be machined in the production alloy; a pre-production part that must behave like the molded one needs to be molded.
A good prototype RFQ says what the prototype is for, which features must match production and which may differ, how many parts and by when. It keeps tolerances loose except where fit or function is being tested, and it asks the shop to flag features that will be expensive in production, so the prototype teaches you about cost as well as function.
RFQ checklist
15 things to settle on the drawing or in the request before you ask for prototype part quotes. Print it and tick it off against the print, or copy it into the RFQ.
Purpose
What the prototype must prove: form and fit, function, strength or fatigue, appearance, or the production process itself
Purpose picks the process. A printed fit-check part costs a fraction of a machined one; a printed stand-in tells you little about the strength of the metal part.
Features that must be production-representative, and features that may differ
Allowing a tapped hole instead of an insert, a different radius, or a machined version of a molded snap fit can cut price and lead time sharply.
The intended production process and volume
A shop that knows the part will be die cast or molded can match draft and wall thickness now and warn about features that will not transfer.
Material and process
Material: the production material, or an acceptable stand-in (for example 6061 for a cast aluminum part, or an ABS-like resin for molded ABS)
Production alloys and resins may not exist in the prototype process or in stock sizes. A stand-in that behaves close enough is often the fastest route.
Process preference, or permission for the shop to choose
Shops know which of their machines or printers will make the part fastest at acceptable quality.
Heat treatment and finishes, only if the test needs them
Anodizing, plating and heat treatment each add days to a week or more. Skip them unless the test depends on them.
Geometry and tolerances
Critical dimensions for fit or function, and a general tolerance for the rest (for example ISO 2768-m)
Tight tolerances on a prototype buy nothing unless you measure against them.
Threads: cut or tapped, printed, or threaded inserts
Printed threads are weak and imprecise. Inserts or tapping after printing are cheap fixes, but only if the shop knows you want them.
Surface finish and cosmetic requirements
Show-quality finish (sanded, painted, textured) is handwork. For a function test, as-machined or as-printed is fine.
Assembly and hardware, if parts ship assembled
Assembly time and purchased hardware belong in the quote.
Quantity, timing and feedback
Quantity, and how many more iterations you expect
One part versus five changes the process choice, and fast iterations make one responsive shop worth more than the lowest single price.
The date you need parts, and whether you will pay for expedite
Many prototype shops quote standard and expedited lead times. A date gets a real answer; "ASAP" gets the expedite price.
Design-for-manufacturing feedback requested
Asking the shop to mark what would be cheaper in production gets advice from people who make parts all day.
Inspection needed: none, key dimensions, or a full report
A full inspection report on a quick-turn prototype can cost as much as the part.
Confidentiality: an NDA, if the design is unreleased
Most shops sign one readily; do it before sending the files.
What to send with the RFQ
- A STEP model (and STL for printing, if you have it), plus a drawing only for the features that need tolerances, threads or finish.
- What the prototype is for and which features matter.
- Quantity and required date.
- The intended production process and volume.
- Material, or the properties a stand-in material must have.
Lead times
| Prototype or first parts | Printed plastic parts: 1-5 days. Machined parts in common materials: 3 days to 2 weeks. Sheet metal: 1-2 weeks. |
|---|---|
| Production or repeat orders | Moving toward production: aluminum prototype molds and bridge tooling take about 2-6 weeks to first shots; investment castings from printed patterns about 2-4 weeks. |
Typical of U.S. job shops, from order or approved drawing to shipment; confirm with the shop for your part.
What drives the cost
- Lead time: expedited prototypes carry a significant premium over standard lead time.
- Process: printing is cheapest for complex plastic shapes; machining for metal and precise features.
- Tolerances and surface finish beyond what the test needs.
- Material availability: exotic alloys and resins that must be ordered in.
- Secondary operations: finishing, heat treatment, inserts and painting.
- Quantity: setup dominates the price of a single part.
Common mistakes
- Production tolerances on a first-look prototype.
- Testing strength in a printed stand-in and expecting the metal part to behave the same.
- Designing the prototype for machining when production will be molded or cast.
- Asking for "ASAP" instead of a date.
- Paying for cosmetic finish on a part that will be cut up in testing.
Questions to ask the shop
- Which process would you use for this purpose, and what would the next-best option cost?
- Which features would you change for production, and why?
- What materials do you have in stock now?
- What are your standard and expedited lead times?
- Can you also make the production version, or recommend who does?
Typical processes
Typical materials
Charts and calculators
Frequently asked questions
- 3D printing or CNC machining for a prototype?
- Print when the geometry is complex, a plastic will do, and the test is form, fit or early function: it is faster and cheaper for one or two parts. Machine when the part must be in the production metal or engineering plastic, hold tight tolerances, or carry real loads. Metal printing fills a narrow gap: complex metal geometry that cannot be machined.
- How many prototypes should I order?
- Enough for the tests plus one or two spares: tests break parts, and a second part lets you see variation. Setup is most of the cost of one part, so the second and third are usually cheap.
- Do I need a drawing for a prototype?
- Not for every feature. A STEP model is enough for most prototype shops, with a short drawing or marked-up PDF for the dimensions that must be held, threads and finish. Anything not called out is made to the shop's standard tolerance.
Build the RFQ: attach the print and this checklist
Attach the drawing (PDF) and the model (STEP), and put your answers to the checklist in the description. A Noramark sourcing specialist matches the request with U.S. shops that make prototype parts and contacts you within 1 business day.
