Receiving a prototype is not the same as accepting it. The box arrives, the parts look right at a glance—and the problems are found in the second hour, after the supplier has moved on. The fix is a review checklist: visual and surface inspection, dimensional checks on the critical features, assembly and function testing, and a match of the parts to the reports. This guide provides the checklist and a feedback template for the findings.
Receiving Is Not the Same as Accepting
Acceptance is a decision, not a moment of opening the box. The parts should be reviewed against the drawing, the specification, and the reports before they are declared acceptable. The review is the buyer's quality gate, and it protects both sides: it catches the problem early, and it documents the acceptance.
The practical habit is to schedule the review while the project is still fresh—within days of receipt—and to record the findings in writing. The prototype that is reviewed carefully produces a clear next step; the one reviewed casually produces surprises later.
The review's timing is part of the process. The prototype is reviewed within days of receipt, while the project is fresh and the supplier is responsive; a delayed review loses the context. The buyer should schedule the review with the receipt, because the timing is the process. The review that is timely is the one that is effective.
The review's record is the project's memory. The findings, the photos, and the decisions are recorded and shared, so the next round and the next supplier know the history. The buyer should keep the review record, because the memory is the continuity. The project that is recorded is the one that continues.
Visual and Surface Inspection
The first pass is visual: the part against the drawing, the surfaces against the finish requirement, and the edges against the specification. Check for the obvious—wrong geometry, missing features, surface defects, burrs, and damage in transit.
The visual check is also the finish check: color, texture, and surface quality against the sample or reference. A defect that is acceptable on a prototype may not be on a production part, and the finding should be recorded either way. Photographs at receipt document the state for both sides.
The visual review's references are the drawing and the sample. The part is compared with the geometry, the finish, and the reference sample, and the deviations are noted. The buyer should review against the references, because the visual check is a comparison. The part that is compared is the one that is judged.
The surface review's scope is the functional and the visible surfaces. The sealing face, the A-side, and the edges are checked for the defects that matter; the hidden surfaces are sampled. The buyer should scope the surface check, because the inspection follows the risk. The check that is scoped is the one that is efficient.
Dimensional Checks on Critical Features
The critical dimensions are the ones that affect function: mating surfaces, fits, and mounting features. Measure them against the drawing, using the same measurement logic the inspection report used. The comparison is the evidence: does the part meet the called-out tolerance?
The check should focus on the features the drawing marks as critical, not every dimension. A prototype reviewed against the critical set finds the fit and function problems; the rest of the dimensions are the supplier's process responsibility.
The dimensional review's instruments follow the features. The calipers, the micrometers, the gauges, and the CMM are matched to the critical dimensions, and the readings are compared with the drawing. The buyer should verify the instruments' suitability, because the measurement is the evidence. The reading that is capable is the one that is trusted.
The dimensional review's tolerance logic is the drawing's. The critical dimensions are checked against their callouts, and the non-critical dimensions are accepted on the process control. The buyer should check the critical set, because the function is in the critical values. The review that is focused is the one that is useful.
Assembly and Function Testing
The prototype's purpose is assembly and function. Assemble the parts, check the fits and the clearances, and run the function the prototype was built to prove. The assembly check validates the geometry; the function test validates the behavior.
The pass criteria come from the test plan written before the order. A fit that assembles with the designed effort, a mechanism that runs through its range, and a function that meets the criterion are the acceptance evidence. The failures found here are the findings that drive the next revision.
The assembly review's sequence is the assembly logic. The parts are assembled in the production order, the fits are checked at each step, and the clearances are verified. The buyer should assemble in the order, because the assembly logic is the test. The assembly that is sequenced is the one that is understood.
The function test's criteria are the acceptance. The motion, the load, and the cycling are run against the criteria written before the order, and the result is a pass or a finding. The buyer should test against the criteria, because the acceptance is the decision. The test that is criteria-based is the one that decides.
The assembly test is the prototype's first real-world check. The parts are put together with the intended fasteners, the motion is cycled, and the fit is evaluated against the drawing; the prototype that assembles and functions is the prototype that answers the program's question, while the one that only looks right on the bench leaves the question open.
The function test then runs the prototype through its operating motion, and the friction, the clearance, and the load behavior are observed; the findings are recorded against the intended function, and the fixes go into the next revision.
Matching Parts to Reports
The parts and the reports should agree. The inspection report, the material certificate, and the drawing revision should match what is in the box: the material on the certificate is the material in the part, the measured values on the report match the measured part, and the revision matches the order.
The mismatch is the red flag. A part that does not match its report, or a certificate for the wrong revision, is a process problem, not a paperwork detail. Record it and ask the supplier to reconcile before acceptance.
The report reconciliation is a traceability check. The material certificate matches the part's material, the inspection report matches the drawing revision, and the records tie the part to its history; the mismatch breaks the chain. The buyer should check the chain, because the traceability is the part's identity. The part that is traceable is the one that is accepted.
The reconciliation is documented with the review. The mismatch, the supplier's response, and the resolution are recorded, and the record closes the finding. The buyer should document the reconciliation, because the prototype program's history is in the records. The finding that is closed is the one that is done.
A Feedback Template for Revisions
When the review finds issues, send the findings in a structured format:
Prototype review — Order [ID], received [date]
1. Accepted: [features that passed]
2. Issues:
- [Issue]: [what was observed] / [expected] / [photo or measurement]
3. Required changes: [revision request]
4. Verification: [what will be checked on the next round]
5. Decision: [accept with changes / reject / approve for next stage]
The template turns findings into a decision and gives the supplier a clear revision target.
Order Your Prototype with Reports Included
Prototype acceptance is a checklist, not a glance. Visual and surface checks, dimensional verification of critical features, assembly and function testing, and a match to the reports produce the evidence to accept or revise.
6CProto's rapid prototyping service can include inspection reports with the order, and the quality documents guide (CT01) covers the full document set. When you request a quote, state which reports should accompany the parts, and the review checklist will have its evidence waiting.
The report scope is set with the order. The inspection report, the material certificate, and the dimensional data are specified in the RFQ, and the parts ship with them; the review checklist finds the evidence waiting. The buyer should set the report scope with the order, because the documentation is part of the deliverable. The order that is specified is the one that is complete.
The review checklist is also the supplier's feedback. The findings are returned in the structured template, the supplier responds with the fixes, and the loop closes; the review is a two-way exchange. The buyer should run the loop, because the prototype program improves in the exchange. The loop that closes is the one that progresses.
Conclusion
Prototype acceptance is a documented review, not a moment of receipt. Visual and dimensional checks, assembly and function testing, and a match to the reports produce the decision to accept or revise. The checklist makes the review consistent, and the template makes the findings actionable.
The next step is to define the critical features and the required reports before the order, then run the checklist when the parts arrive.
The review checklist is the acceptance discipline. The parts are reviewed against the drawing, the reports, and the plan, and the acceptance is documented; the discipline protects the program. The buyer should keep the discipline, because the acceptance is the quality gate. The gate that is kept is the one that protects.
The review checklist is a template that improves with use. The findings from each project refine the checklist—the features to check, the evidence to request, the formats to use—and the template gets sharper. The buyer should maintain the template, because the checklist is a learned tool. The template that improves is the one that protects.
The review checklist is also the supplier's feedback loop. The findings are returned, the supplier's fixes are verified, and the learning is shared; the loop builds the working relationship. The buyer should run the loop, because the prototype program improves in the exchange. The loop that runs is the one that progresses.
FAQs
What should I check when a prototype arrives?
Visual and surface condition, the critical dimensions against the drawing, assembly and function, and a match between the parts and the inspection reports.
How do I know which dimensions to measure?
The critical ones—the features the drawing marks as functional: mating surfaces, fits, and mounting features. Focus the review there rather than measuring everything.
What if the parts do not match the reports?
Record the mismatch and ask the supplier to reconcile before acceptance. A part that does not match its report is a process problem worth resolving in writing.
How should I send revision feedback?
In a structured format: what passed, what failed with evidence, the required changes, the verification for the next round, and the decision. The template gives the supplier a clear revision target.