Last updated: 2026-09-04 · 5 min read

T2 Sample Inspection — What Must Be Verified After the Mold Modification, and How Do You Confirm That the Fix Resolved the T1 Issues Without Introducing New Ones?

The T2 trial confirms that T1 modifications fixed the out-of-spec dimensions and did not create new defects. Unlike T1 (full dimensional scan), T2 inspects only the dimensions that were out of spec at T1, plus the cosmetic and functional features affected by the modification. A successful T2 produces parts that meet all drawing requirements and authorizes the mold for production.

Key Facts

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  • T2 scope is narrower than T1: only re-measure the out-of-spec dimensions from T1, plus affected cosmetic and functional features. T1 measures every critical dimension; T2 measures only what changed.
  • Decision tree: T2 passes → production; T2 partially passes → T3 (same focused scope); T2 introduces new problems → root cause investigation before T3; 4+ trials without resolution → fundamental design or DFM problem.
  • Cost per additional trial: $300–800 in machine time and material. T1-to-T2 cycle: 2–3 weeks (modification 3–10 days + trial 3–5 days + documentation 5 days). Default: mold maker covers T1 and T2; T3+ charged separately unless root cause is mold maker’s error.

    • Gate vestige — The visible mark left on the part surface where the gate was trimmed. Edge gate: 0.5–2.0mm vestige. Pin-point gate: 0.2–0.5mm. Valve gate: 0.05–0.1mm (flush). Vestige size affects cosmetic appearance and may require secondary trimming. The related guide covers adjacent topics.

    What Does the T2 Inspection Checklist Include — and How Does It Differ From T1?

    Five inspection items, scoped to the modification:

    Inspection Item T1 Scope T2 Scope Acceptance Criteria
    Out-of-spec dimensions from T1 All critical dimensions measured Only the out-of-spec dimensions re-measured All within tolerance on T2 samples
    Cosmetic defects (sink, flash, weld lines) Full cosmetic inspection Check only areas affected by the modification No visible defects at 30 cm under normal lighting
    Functional fit (mate with mating parts) Full fit check if mating parts available Fit check on the modified features Parts mate without force or gap
    Process parameters Full process sheet recorded Verify parameters match T1 (within ±10%) Cycle time within T1 ±10%; no new adjustments needed
    Mold condition (video, photos) Full documentation package Updated video showing modified areas running No sticking, flashing or cycle interruptions

    The T2 trial runs 50–100 shots, same as T1. The first 10 shots are discarded to allow the mold to thermal equilibrium. The next 20–50 shots are used for measurement and inspection. If the T2 samples pass all acceptance criteria, the mold is approved for production. If any dimension is still out of spec, the mold requires further modification and a T3 trial.

    What Is the Decision Tree After T2 — and How Many Trials Are Acceptable?

    1. T2 passes all criteria. The mold is approved for production. The customer signs the T2 sample approval form, the mold maker ships the production samples and the mold enters the production queue.
      The T2 documentation package (updated CMM report, process sheet, video) is filed as the production baseline.
    2. T2 partially passes (some dimensions still out of spec). The mold requires further modification. The mold maker identifies the remaining issues, proposes the corrective action and schedules a T3 trial.
      The T3 trial follows the same inspection scope as T2 — only the remaining out-of-spec dimensions are checked.
    3. T2 introduces new problems (modification fixed one issue but created another). This indicates the modification was not properly analyzed — the fix addressed the symptom but not the root cause. The mold maker must re-run the mold flow analysis and re-evaluate the modification before proceeding.
      The T3 trial scope expands to include both the original issues and the new issues.
    4. More than 4 trials (T4+) without resolution. If the mold requires more than 4 trials, there is a fundamental problem with the mold design, the mold flow analysis or the DFM review. Each additional trial costs $300–800 in machine time and material — the accumulated cost may exceed the cost of building a new mold with a corrected design.
      Stop and investigate before continuing.

    The contract should specify which party bears the cost of T2 and subsequent modifications. The default in the mold making industry is that the mold maker covers T1 and T2 trials; T3 and beyond are charged separately unless the root cause is clearly the mold maker’s error.
    If the T1 issue was caused by a design change requested by the customer after the mold was cut, the customer pays for the modification and all subsequent trials.

    Ejector pin — A steel pin that pushes the molded part out of the cavity after cooling. Typical diameter: 2–10mm. Pin marks are visible on the part surface — position at non-cosmetic areas. Pin count and placement affect ejection force and part warpage. The related guide covers adjacent topics.

    Each additional trial after T2 costs $300–800 in machine time and material. If the mold requires more than 4 trials, the accumulated cost may exceed the cost of building a new mold with a corrected design. The rule: stop and investigate the root cause before continuing.

  • Key parameter identified — critical variable confirmed against spec.
  • Tolerance within achievable range — commercial ±0.15mm or tighter as needed.
  • Material matched to application — resin grade selected for end-use environment.
  • Process window validated at T1 — parameters locked after first trial.
  • Inspection method defined — CMM, visual, or functional test specified.

    • Frequently Asked Questions

    How long does the T2 trial take after the mold modification is completed?

    The T2 trial is typically completed within 3–5 working days of the mold modification being finished. The modification itself takes 3–10 working days depending on the scope — a simple dimension change takes 3 days; a complex modification with welding and re-machining takes 7–10 days.

    After the modification, the mold is re-assembled, the cooling lines are re-connected, and the trial is run. The T2 documentation package is delivered within 5 working days of the trial. The total T1-to-T2 cycle is typically 2–3 weeks.

    Who pays for the T2 trial — the mold maker or the customer?

    If the T1 issue was caused by a mold design or machining error, the mold maker pays for the modification and the T2 trial — this is covered by the mold warranty. If the T1 issue was caused by a design change requested by the customer after the mold was cut, the customer pays.

    The contract should specify which party bears the cost of T2 modifications. The default: mold maker covers T1 and T2; T3 and beyond are charged separately unless the root cause is clearly the mold maker’s error.

    Can you approve the mold for production based on T2 samples alone — or do you need a full CMM report?

    The T2 approval requires an updated CMM report that shows the modified dimensions are now within tolerance. The CMM report must include the actual measured values (not just “OK”), the deviation from nominal, and the CMM operator’s signature.

    Visual inspection of the samples is not sufficient — the CMM data is the only objective evidence that the modification was successful. The T2 CMM report is filed alongside the T1 CMM report as the production baseline for future quality audits.

    Key Takeaways

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  • T2 confirms that T1 modifications fixed the issues without introducing new problems.
  • T2 inspection is focused: only re-measure out-of-spec dimensions from T1, plus affected cosmetic and functional features.
  • Decision tree: T2 passes → production; T2 partially passes → T3; T2 introduces new issues → root cause investigation.
  • More than 4 trials indicates a fundamental design or DFM problem — stop and investigate.

    • If you have received T2 samples and need help evaluating the CMM data, process parameters or cosmetic condition, send the T2 documentation package for an independent review.
    The review confirms whether the T1 modifications were successful, identifies any remaining issues, and recommends whether the mold is ready for production or requires further modification.

    Sources: Society of Plastics Engineers (SPE) — Mold Trial Standards · ASTM International — First Article Inspection per AS9102 · AIAG — PPAP Manual, 4th Edition · LKM Mold Base Standards · HASCO Standard Parts Catalog

    — Arthur, Tooling Engineer at aCatMould