Rapid Prototype Companies: How to Compare Them Without Guessing
This guide is for engineers and sourcing managers shortlisting rapid prototype companies in China. It covers the checks that predict whether a shop can hold your tolerances, hit your dates, and scale from one part to 10,000. Read it before you send an RFQ.
In this article
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
What matters most when comparing rapid prototype companies
Prototype shop types and what they are good for
Match the shop type to your part before you compare price.
| Shop type | Typical tolerance | Good fit | Watch out for |
|---|---|---|---|
| Job shop, 3-axis only | ±0.05 mm | Simple brackets, plates, fixtures | Undercuts and 5-face work need re-fixturing |
| Multi-axis machine shop | ±0.005 mm | Complex housings, impellers, medical parts | Higher hourly rate; ask for CMM reports |
| 3D printing bureau | ±0.1 mm | Early form checks, jigs, low-load covers | No functional threads or tight bores |
| Vacuum casting shop | ±0.15 mm | 10–50 cosmetic housings before tooling | Silicone molds wear out after about 20 pulls |
| Full-service factory | ±0.005 mm | Prototype to 10,000+ part runs | Needs clear drawings and finish specs up front |
| Die casting supplier | ±0.1 mm | High-volume zinc or aluminum housings | Tooling lead time and cost only pay off past 2,000 parts |
| Sheet metal shop | ±0.2 mm | Enclosures, chassis, brackets | Tight bend radii need a bend allowance review |
A simple scorecard for shortlisting rapid prototype companies
Score each shop 1–5 on these rows. Total below 22 is a pass.
| Criterion | Weak signal | Strong signal |
|---|---|---|
| Tolerance evidence | Caliper reading on request | CMM report with datum scheme |
| DFM feedback | No comments on the model | Written DFM within 12 hours |
| Lead time detail | One number, no milestones | Material, machining, finish, ship dates |
| MOQ | 500-piece minimum | No minimum order quantity |
| Certifications | ISO 9001 only, no scope | ISO 9001, IATF 16949, ISO 13485, ISO 27001 |
| Quote breakdown | Single line item | Material, machining, finishing, inspection |
| Engineering access | Sales contact only | Named process engineer |
| Scale path | New fixture for every batch | Same process from prototype to production |
The shop that answers technical questions fastest usually wins
Price matters, but a shop that reads your model, flags thin walls, and returns a CMM report will cost you less over the program than one that quotes low and re-cuts twice. Pick on evidence, not on rate.
Check 1: Can the shop actually hold your tolerance?
Tolerance claims on a website are easy. The question is whether the shop has the spindles, fixturing, and metrology to repeat ±0.005 mm across a batch, not just on one sample. Ask which machine will run your part. A 3-axis mill with a vise can hold ±0.05 mm all day. Getting to ±0.005 mm usually needs a temperature-stable room, a 5-axis center, and a probe or CMM to close the loop.
The second question is how they measure. A caliper reading is not a tolerance report. For anything with a true position callout or a concentricity requirement, ask for a CMM report with the datum scheme shown. If the shop cannot tell you which datums they used, the number they quote is a guess.
Third, ask about wall thickness and feature size floors. Thin walls below 0.5 mm in aluminum deflect under cutting load, and deep pockets with a 3:1 depth-to-diameter ratio need long-reach tooling that flexes. A shop that flags these before quoting is reading your model. One that just returns a number is not.
Finally, check the material. 6061-T6 machines cleanly and holds tight tolerances. 316L stainless work-hardens and moves under heat. Inconel and Ti-6Al-4V need slower feeds, more tool changes, and a shop that has cut them before. A low quote on titanium from a shop that mostly runs aluminum is a red flag, not a bargain.
- 1Ask which machine and which fixtureIf the answer is vague, the tolerance is aspirational.
- 2Require a CMM report for critical featuresDatum scheme on the drawing, measured values on the report.
- 3Flag thin walls under 0.5 mm earlyThey change the cut strategy and the price.
- 4Match the material to the shop's historyTitanium and Inconel quotes from aluminum-only shops tend to come back with problems.
Check 2: What does the lead time actually include?
A quoted lead time is a promise about a chain of events: DFM review, material purchase, programming, machining, finishing, inspection, and packing. If the shop quotes three days but the material is not in stock, the clock has not started. Ask when the material arrives, not when the order is placed.
A reliable shop can return a quotation and a free DFM analysis within 12 hours and start production within 24 hours of PO and drawing sign-off. Parts typically ship in 3–5 days for standard prototype work. Treat anything faster with suspicion unless the shop already stocks your material and has spare capacity that week.
Ask what happens if a feature fails inspection. A shop that re-cuts the part the same week absorbs the problem. One that puts you back in the general queue adds a week. The difference is not in the quote, it is in how the shop schedules rework.
Also separate prototype lead time from production lead time. The first article may take five days. A 10,000-piece run has a different schedule, and the shop should quote both so you can plan the transition instead of discovering it after design freeze.
- 1Define the clock startPO, drawing release, or material arrival. Get it in writing.
- 2Ask for the DFM turnaround12 hours is a normal target for a shop that reviews models before pricing.
- 3Ask how rework is scheduledSame-week rework is the real lead time guarantee.
- 4Quote prototype and production separatelyThe rates and the schedule are not the same.
Check 3: Does the MOQ match your program stage?
A shop with a 500-piece minimum is not set up for prototypes, no matter what its landing page says. If you are validating a design, you need a supplier that will run one part without a setup surcharge that doubles the unit price. No minimum order quantity is the right answer for prototype work, and it should not change the tolerance or the inspection routine.
The reverse also matters. A prototype shop that never scaled past one-offs will struggle when your design freezes and you need 10,000 parts a year. Ask what volume the shop runs regularly. A supplier that handles one prototype to 10,000+ part runs can carry the program through without a second qualification cycle.
Pricing structure tells you where the risk sits. A quote that is one line item hides the cost of fixturing, programming, and inspection. A quote that breaks those out lets you compare shops fairly and see which one is charging for engineering that you actually need.
Watch for finishing quoted as an afterthought. Anodizing, plating, and powder coating add days and can change dimensions. A shop that lists finishes and their dimensional impact up front is easier to plan around than one that treats finishing as a separate universe.
- 1Prototype stage: no MOQOne part should be priced as one part, not as a fraction of a batch.
- 2Production stage: ask the volume ceiling10,000+ parts a year is a different operation than one-off machining.
- 3Ask for a broken-out quoteMaterial, machining, finishing, and inspection as separate lines.
- 4Check finishing lead time earlyAnodizing and plating add days and can affect tolerances.
Check 4: Do the certifications cover your industry?
ISO 9001:2015 is the baseline. It says the shop has a documented quality system and audits it. For a bracket or an enclosure, that is enough. It does not say anything about traceability for implants or process control for automotive parts.
Medical device programs usually need ISO 13485:2016. Automotive and EV programs usually need IATF 16949:2016. If a supplier claims these but cannot show the certificate scope, ask for the certificate number and the issuing body. The scope matters as much as the standard.
Data handling is a separate question. ISO 27001:2022 covers information security, which matters if your models and drawings are confidential. Ask how files are transferred, who has access, and whether an NDA is available before you upload anything. Secure uploads and confidential handling should be the default, not a paid extra.
Also check inspection practice. 100% inspection before shipment, with raw material checks, in-process monitoring, and final inspection, is the standard a serious shop will describe without prompting. Reports should be available on request, and for regulated parts they should be automatic.
- 1ISO 9001 is the floorFine for general industrial parts.
- 2ISO 13485 for medicalAsk for the certificate scope, not just the logo.
- 3IATF 16949 for automotiveRequired for most tier supply chains.
- 4ISO 27001 for data securityRelevant when drawings are confidential.
Check 5: What the quote is not telling you
The lowest quote often excludes something. Maybe the finish is as-machined at Ra 1.6–3.2 μm when your drawing calls for Ra 0.8–1.6 μm. Maybe the tolerance is a best-effort number with no inspection report. Maybe the price assumes you accept a visible tool mark on a cosmetic surface.
Ask what the quote assumes. If the shop cannot name three assumptions, it has not read the drawing carefully. Common assumptions include material condition, surface finish, inspection level, and whether hardware is installed.
Another trap is the sample that does not match the production process. A shop may hand-finish a one-off sample that looks perfect, then run the batch on a different machine with a different fixture. Ask whether the sample and the production parts come off the same process. If not, ask what is different.
Finally, be wary of a shop that will not name a contact engineer. A sales-only interface slows down every technical question and turns a two-email clarification into a week of back and forth. Direct access to a process engineer is worth more than a small discount.
- 1Surface finish is a common omissionAs-machined and fine finish are different processes and prices.
- 2Ask for three quote assumptionsIf there are none, the drawing was not read.
- 3Confirm sample and batch use the same processHand-finished samples hide production problems.
- 4Get an engineer contactIt shortens every technical clarification.
Check 6: Can the shop scale without re-qualifying?
Prototype work is one problem. Production is another. A shop that machines 127 high-precision CNC machines across three wholly-owned plants, including 16 simultaneous 5-axis machining centers, 12 four-axis mills, 27 three-axis machines, and 16 mill-turn centers, has the capacity to move a part from prototype to volume without a new supplier qualification.
Size limits matter too. A 4,000 mm maximum processing size with travels up to 4,000 × 400 × 150 mm covers long parts like rails and beams. Medium travels of 750 × 1,150 × 550 mm and 600 × 600 × 600 mm cover most enclosures. Compact travels of 500 × 500 × 450 mm and 500 × 310 × 200 mm handle small precision parts. A Ø400 mm rotary table supports round work that would otherwise need a second setup.
Ask what happens when your volume triples. If the answer involves a new machine purchase and a new fixture design, that is a schedule risk. If the shop already runs that part size on multiple machines, the transition is a scheduling question, not an engineering one.
Material range is part of scaling. A shop that stocks or regularly sources 6061, 7075, 304, 316L, 17-4PH, Ti-6Al-4V, and engineering plastics can absorb a design change without a long material lead time. A narrow material list is a constraint you inherit.
- 1Capacity across machine types5-axis, 4-axis, 3-axis, and mill-turn in one plant reduces handoffs.
- 2Travel range covers small to 4,000 mm partsCheck your largest part against the travel list before quoting.
- 3Ask how volume increases are absorbedMultiple machines for the same part size is the low-risk answer.
- 4Confirm material availabilityA broad stocked range avoids long material lead times.
How to run the comparison in one week
- 1Day 1: Prepare one drawing and one modelSend the same STEP file and 2D drawing to every shop. Include datums, critical features, surface finish callouts, and material condition. A shop that quotes from the model alone will miss the tolerance callouts.
- 2Day 2: Ask four questions with the RFQWhich machine will run this part? What is the DFM turnaround? What is the MOQ? Which certifications apply? The answers separate shops faster than price does.
- 3Day 3: Compare quotes line by linePut material, machining, finishing, inspection, and freight on the same sheet. A low total with a missing finishing line is not lower, it is incomplete. Normalize the surface finish to Ra 0.8–1.6 μm before comparing.
- 4Day 4: Ask for one CMM report from a past jobPick a part with a true position or concentricity callout. The report should show measured values and the datums used. If the shop will not share one, treat the tolerance claim as unverified.
- 5Day 5: Order a single test partOrder one piece from the top two shops. Inspect it against the drawing, not against the sample photos. Check threads, bores, and finish. One paid part tells you more than three reference calls.
- 6Day 6–7: Review the communication trailCount how many emails it took to get a technical answer, and whether an engineer was involved. If a prototype order takes five emails, a production change order will take twenty.
Questions buyers ask before choosing a prototype supplier
How many rapid prototype companies should I quote?
Three is enough for most programs. Two will usually be close on price, and the third shows you what the market looks like. More than four adds work without changing the decision.
Send identical files and ask identical questions. If one shop answers a question the others ignored, that is data.
Is a lower tolerance number always better?
No. A ±0.005 mm callout on a non-critical feature raises cost and inspection time without adding function. Apply tight tolerances only where the design needs them.
A shop that asks why a tolerance is tight is doing its job. One that accepts every callout without comment may not be inspecting to it.
What MOQ should a prototype order expect?
One piece. Prototype work exists to validate a design before tooling, so a minimum order quantity defeats the purpose. Setup cost belongs in the unit price, not in a batch requirement.
If a shop insists on 500 pieces, it is a production supplier. That is fine, but it is not the right partner for a first article.
Do I need ISO 13485 or IATF 16949 for a prototype?
For the prototype itself, usually not. For the program that follows, yes. If you know the part will end up in a medical device or a vehicle, starting with a supplier that already holds the certificate avoids a second qualification cycle later.
Ask for the certificate scope, not just the standard number. A certificate can cover a different site or a different product family.
How do I check that files stay confidential?
Ask how uploads are transferred, who can open them, and whether the shop holds ISO 27001:2022. Then sign an NDA before sending production drawings.
A shop that treats confidentiality as standard practice will answer these questions without hesitation. One that does not may not have a process at all.
What should a first article inspection report include?
Measured values for every dimension on the drawing, the datum scheme used, the inspection instrument, and the operator or inspector identification. For critical features, a CMM report rather than manual measurements.
Ask for the report before shipment, not after. A report that arrives with the parts cannot prevent a bad batch from shipping.
Send one drawing and see how the shop reads it
Upload your model and drawing. You get a quotation and a free DFM analysis within 12 hours, with the assumptions written out so you can compare us against your other quotes.
12-hour quote100% inspectionNo MOQNDA available
More from the shop floor
We publish setup notes, tooling trials and inspection data from the factory floor.
