MANUFACTURING / JAPAN SOURCING

Metal stamping: separate prototype approval from production die and part approval

Record how the prototype was made and what it proved. Then agree the production tooling, trial conditions and evidence needed before accepting the die, the parts and the start of routine supply.

Record what made the prototype pass

Imagine a sheet-metal bracket that fits an assembly in a prototype build. The prototype was trimmed and adjusted by hand, while the production proposal uses a progressive die. The fit check is useful, but it does not establish what the production process can repeatedly deliver.

Keep the drawing revision, material grade and temper, thickness, blanking/trimming method, forming route and any hand correction with the sample. MEC describes prototype press work using simplified tooling, followed by laser trimming and manual assembly arrangements.[1] This is one example of why a sample’s appearance alone does not identify the process behind it.

List what was checked: assembly fit, hole position, bend geometry, edge condition, or another functional requirement. Record what was not assessed and any accepted deviation. Carry that knowledge into the next trial without calling the prototype a production-process approval.

Agree what the production die must be tried on

Ask which operations and tooling will make the production part and which features differ from the prototype route. Identify the material, tool revision, intended press and feeding or transfer arrangement. Mutsumi describes reviewing the product drawing, quantity and press before proposing a die, then checking products through tryout and measurement.[2]

For the bracket example, link the critical holes, bend location and mating surfaces to the drawing. Ask whether measurements are taken free, supported or clamped, and before or after deburring, coating or other finishing. If a part needs manual correction to meet the drawing, record that operation and whether it is included in the production proposal.

Keep the prototype, production trial and approval scope distinct

1Prototype: retain its manufacturing route, checked function and deviations
2Production trial: identify material, die, press and measurement state
3Decisions: record separately the accepted die scope, parts and supply release

An approval record map, not a die design or press operating sequence. Arrows carry information; they do not indicate that one accepted sample automatically approves tooling or serial supply.

Use production-trial evidence for the production decision

Agree the trial plan with the supplier: conditions to represent, quantity or duration, sample identification, inspection features and how any changes will be recorded. The needed evidence depends on the part and the buyer’s requirements; a universal sample count or capability target is not supplied here.

Retain the measurement results and the condition in which each sample was produced. Mutsumi describes measuring tryout products and comparing them with requirements.[2] A selected first piece is not by itself evidence of stability across the intended run. If the trial is on different equipment or uses temporary handling, identify what still needs confirmation on the proposed production arrangement.

Which decision does each record support?
Decision	Evidence to retain	Question still to resolve
Prototype function	Route, sample IDs, drawing and fit/function results	Which features and processes were not represented?
Production die scope	Tool revision, required operations, interfaces and trial plan	What remains to be tried on the intended equipment?
Production parts	Material, trial conditions, measured features and deviations	Do the agreed part requirements hold under those conditions?
Routine supply	Approved conditions, inspection/lot records and unresolved items	Who releases supply and how are changes reviewed?
Tooling arrangements	Included work, keeping/maintenance and delivery conditions	What does the tooling payment actually cover?

Write down what is accepted and what remains open

Separate the decision on tooling work from acceptance of the parts produced and release of routine supply. Record the responsible reviewer, drawing/tool revisions, evidence, exceptions and any follow-up trial. If one decision is conditional, carry the condition into the order rather than summarising everything as “sample approved”.

Clarify whether you are buying tooling, parts made with the supplier’s tooling, or both. Komatsuseiki describes integrated die and part production while explicitly stating that it does not sell its dies.[3] Ask what the proposed tooling charge covers, where the die is kept, maintenance responsibility, included documents and any agreed handover arrangements. Paying a tooling line does not, by itself, describe those terms.

Before serial supply, identify changes that need review, such as material condition, die repair, forming route or production location. Keep a retained reference and inspection records with the agreed version; a reference part does not replace the drawing or required measurements. For a sourcing enquiry, send HAM the prototype route and results, production plan, quantity, destination and decisions still open.

Questions to send your supplier

Open supplier questions

Part function, drawing revision and destination:
Material grade/temper, thickness and required finished state:
Prototype method, sample IDs, manual corrections and deviations:
What did the prototype actually verify, and what was not assessed?
Proposed production operations, die identity/revision and intended press:
Feeding/transfer and differences from the trial equipment or handling:
Critical features, burr/edge requirements, forming and finishing:
Measurement datums, support/clamping and before/after finishing state:
Trial conditions, samples/run plan, inspection and change records:
Die acceptance, part acceptance and routine-supply release decisions:
Tooling charge scope, keeping/maintenance, documents and handover terms:
Required follow-up, reviewer, quantity and open questions:

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Sources

MEC — Prototype manufacturing
Read prototype press work, laser trimming, simplified fixtures and inspection. Supplier-specific example, not a universal prototype method or inspection rule.
Mutsumi Industry — Press dies
Read specification discussion, intended press, tryout and numerical measurement. Do not transfer equipment capability, acceptance figures, schedule or availability.
Komatsuseiki — Press technology
Read integrated tooling/production description and explicit statement that the company does not sell its dies. Supports asking for commercial tooling scope; no common ownership rule inferred.