The sample approval process is where a plastic sourcing program is won or lost. Tooling quotations can be compared, resin grades specified and audits passed — but none of it matters if the first samples do not match the drawing, the colour standard and the assembly requirements. For buyers, the sample stage is the only point in the program where defects are cheap: a dimension corrected on a T1 sample costs a day of engineering, while the same dimension discovered at the destination port costs the shipment. This guide maps the stages a disciplined sample approval process runs through, what buyers verify at each one, and the documentation that separates a real sign-off from a rubber stamp.
Why the Sample Approval Process Decides the Program
Every plastic part carries a chain of assumptions: that the tool reproduces the drawing, that the compound matches the certificate, that the moulder runs the process the trial established. The sample stage exists to test those assumptions while they are still free to correct. Buyers who treat samples as a formality — glance at the part, file it, release production — transfer the risk to serial production, where corrections mean tool rework, scrap and delays. Buyers who run the stage properly leave it with evidence: dimensional data, a retained master sample and an agreed process baseline that every later production lot can be judged against.
The Stages: T0, T1, T2 and Formal Sign-Off
| Stage | What it is | What the buyer verifies |
|---|---|---|
| T0 | First shots off the tool, often from a temporary or partial setup | Gross dimensions, obvious shorts or flash, gate and ejector marks |
| T1 | Parts from the completed tool under production conditions | Full dimensional report, colour match, material certificate |
| T2 | Rework after T1 deviations, from the final tool | Corrected dimensions, surface finish, cycle stability |
| Formal sign-off | Approval package released for series production | Golden sample retention, control plan, agreed parameter baseline |
The sequence comes from the automotive supply chain, where PPAP — the Production Part Approval Process — formalises it, and where PPAP plastic parts are released against a documented package rather than a conversation. The same logic applies to any plastic sourcing program, however small. The stage names vary between suppliers; the discipline does not. What matters is that each stage has an entry criterion and an exit criterion, and that nothing moves to serial production while an open deviation is unresolved.
What to Check at Each Stage
- Dimensions against the drawing — every critical dimension measured and reported, not sampled; the report should reference balloon numbers from the drawing.
- Colour and finish — against a physical master or Pantone reference, judged under consistent lighting; gloss level matters as much as hue on visible parts.
- Material evidence — a certificate tying the shot parts to the resin lot, plus any required compliance test reports.
- Assembly fit — the sample mated with the adjoining parts, because a part that is individually in tolerance can still fail to assemble.
- Process baseline — the parameter record the samples were moulded under, so production can be compared against it later.
The Documentation Package
A complete plastic sample approval package is small but complete: the dimensional report, the material certificate, the retained master sample (signed and dated by both parties), the process parameter record, and a short deviation list with dispositions. Buyers should insist the master sample is physically retained by both sides — when a dispute arises three months later, the retained sample is the only evidence that cannot be argued with. For T1 sample approval specifically, the deviation list is the heart of the package: it states what is wrong, what will be corrected, and by which stage.
Common Failure Patterns
Three failure patterns repeat across sourcing programs. The first is the verbal approval — a supplier declares the samples good in a message and ships production; when the parts arrive wrong, there is no documented baseline to argue from. The second is the incomplete report: dimensions measured only where the moulder expected them to be in tolerance, with critical features skipped. The third is the skipped stage: T1 deviations waved through to keep a launch date, returning later as field failures. All three are avoided by the same discipline — written criteria, measured evidence, retained samples. Suppliers who accept that structure are usually the ones worth a second order, a point covered in the supplier verification guide; see also the plastic part design guidelines and the wider sourcing guide category. The China plastics company directory lists suppliers by region and specialism.
Related product categories
The materials and part types discussed above are grouped in our sourcing directory:
