A mould trial is the point where design intent meets real material flow. The conversation that follows can either accelerate approval or send the project back to the drawing board. The goal is not to inspect every detail, but to align on the few observations that change your sourcing decision. This means asking for the right evidence, comparing it against your standard, and recording what must be fixed before the next sample. The sections below describe what a buyer can ask, compare, document, clarify, and decide at this exact stage.

What to ask before the trial runs

Before the first shot, confirm the material grade, colour code, and processing conditions the supplier plans to use. Ask for the mould setup sheet and the expected cycle time so you can compare actual performance later. Request a short list of critical dimensions and surface finish targets that will be measured on the first samples.

Make the supplier state which issues they expect to see and which they consider normal process variation. This sets the baseline for the conversation and prevents later disputes about what was agreed. Document these points in writing so the trial has a shared starting line.

• Material grade and colour code
• Processing conditions and cycle time
• Critical dimensions and finish targets
• Expected vs normal variation

How to compare observations against your spec

When the samples arrive, measure the same critical dimensions listed before the trial. Compare each result to your drawing tolerances and flag any value outside that range. Surface defects, sink marks, short shots, and flash should be photographed and matched to your defect standards.

Do not treat every flaw as a blocker. Separate cosmetic issues from functional ones. A minor flow line may be acceptable if the dimension and strength are within spec. Record which observations affect fit, function, or durability and which are purely visual.

• Measure critical dimensions against drawing tolerances
• Photograph and classify surface defects
• Separate cosmetic issues from functional issues
• Record fit, function, and durability impacts

What sample evidence to collect and keep

Collect physical samples, measurement reports, and photos that show each defect at actual size. Ask the supplier for a written deviation report that lists every non-conformance and the proposed correction. Keep all evidence in one folder linked to the purchase order and mould number.

Evidence should answer three questions: what was observed, where it occurred, and how far it deviates from spec. If a dimension is 0.3mm over tolerance, the record must show the measurement, the location on the part, and the drawing value. This makes the next approval traceable.

• Physical samples and measurement reports
• Photos showing defects at actual size
• Written deviation report from supplier
• Folder linked to PO and mould number

How to clarify corrections and trade-offs

For each flagged issue, ask the supplier how they will correct it. A dimensional error may require a mould modification, while a surface defect may need a change in holding pressure or cooling time. Request a timeline and a cost estimate for each correction.

Some corrections may introduce new trade-offs. Slowing the cycle time can reduce sink marks but increase unit cost. Ask the supplier to explain these effects so you can decide which issues are worth fixing now and which can be managed in production. Document the agreed corrections and their impact.

• Correction method for each issue
• Timeline and cost estimate
• Trade-offs between fixes and cost
• Agreed corrections and impact

What to decide before the next approval

Before approving the next sample, confirm that every blocking issue has a verified correction. A blocking issue is one that affects safety, function, or compliance with your spec. Non-blocking issues can be accepted with a documented deviation.

Record the approval criteria in writing. State which dimensions must pass, which defects are acceptable, and which corrections must be re-measured. This creates a visible record that supports the next sourcing decision and prevents rework caused by unclear expectations.

• Verified correction for blocking issues
• Accepted deviations for non-blocking issues
• Written approval criteria
• Re-measurement plan for corrections

How to keep the record visible for the next decision

Store the full trial record in a shared location that all stakeholders can access. Include the original spec, measurement reports, photos, deviation report, and the final approval note. Link this record to the mould number and the next production order.

A visible record lets the next buyer or engineer pick up the conversation without starting over. It also supports audit trails if quality or compliance questions arise later. Update the record after each sample so the trail stays continuous.

• Shared location for all stakeholders
• Spec, reports, photos, and approval note
• Link to mould number and production order
• Updated after each sample

Save the trial record in a shared folder and tag the next buyer before the next sample ships.