Write the decision the prototype must support
“Check the design” is too broad to guide a print. “Check whether the lid can be installed after the cable is connected” gives the team a task that can be observed. Other useful questions concern access to a fastener, the seating of a mating component or whether several parts can be assembled in the intended order.
Choose the questions before specifying an appearance finish. If the prototype exists to reveal an interface, a cosmetic treatment may add work without improving that decision. If the same part must also appear in a presentation, describe the two purposes separately so neither disappears from the scope.
Give each interface a reference
An interface is where one part meets another. Name both sides: cover to base, bracket to mounting plate, or connector to opening. Record whether the reference is a drawing, a current physical component or another prototype. Include its revision. A successful fit against an old component can still leave the next assembly unresolved.
Mark the dimensions that drive those interfaces on an annotated view. Separate the required dimension from the way it will be checked. Some questions need a measurement; others need a physical assembly demonstration. Agree numerical acceptance limits for the particular requirement instead of assigning one tolerance to every feature.
Also identify who supplies the mating parts and who makes the acceptance decision. If the real component will not be available, state what the substitute represents and what the review cannot establish.
Use a short review card during assembly
| Interface or action | Reference to bring | What to observe | Record before the next revision |
|---|---|---|---|
| Panel seating | Current panel or its approved drawing | Does the panel reach its intended seating surface? | Contact location and any obstruction |
| Cable access | Specified connector and cable arrangement | Can the connection be made in the intended order? | Access direction and the area needing change |
| Lid installation | Lid, base and assembly sequence | Can the lid be positioned without disturbing the fitted panel? | Step where interference occurs |
| Fastener access | Proposed fastener and required access route | Can the assembly be reached as planned? | Access limitation, marked on a photograph |
Keep the checklist next to the parts. A photograph with a numbered arrow is often easier to act on than a long message saying that something feels tight. Record observations before choosing the fix; several design features can produce a similar symptom.
Separate what happened from what you think caused it
Use two columns in the review notes: observation and proposed action. “The lid stops at the rear corner” is an observation. “Move the rear locating feature” is a proposed design change. Keeping them separate lets the designer examine other explanations without losing the original evidence.
Label the physical parts with their revision or keep them with a labelled record. Include the assembly configuration and the reference used in photographs. If a part was trimmed, sanded or otherwise altered during the check, record that change; it is no longer an untouched reference for the supplied file.
A fit review answers the questions it was set up to examine. It does not, on its own, establish long-term performance or approval for a production application. A separate test objective needs its own conditions and acceptance evidence.
Change the design with a traceable reason
Summarise each open issue with an owner and a next action: update the CAD, obtain a missing component, change the assembly sequence or repeat a defined check. Keep accepted features visible in the notes so an unrelated revision does not quietly reopen them.
For the next order, identify the new file revision and describe the intended change. Retain the previous part until the comparison is complete. If the next stage is a repeated quantity, use the first-part approval workflow to decide when that quantity may proceed.
A brief for your fit-review prototype
Purpose: Check [specific interface or assembly action]. Parts: [names, quantities and file revisions]. Reference: [mating component or drawing, revision and who supplies it]. Priority checks: [marked dimensions, access and assembly sequence]. Appearance: [surfaces that matter for this review]. Acceptance: [what must be observed or measured, and who decides]. Next step: [design revision, further test or first-part approval]. Required review date and delivery city: [details].
Use the CAD handover checklist to package the files. For a board-and-box assembly, the enclosure planning guide adds questions about connectors, mounting and closure. Our rapid-prototyping enquiry starts with the question your part needs to answer.