Last updated: 2026-09-01 · 4 min read

What Should You Verify at T2 — and How Is It Different from T1?

T2 (the second mold trial) is the verification that the T1 corrections worked and the process is repeatable. While T1 is a discovery trial — establishing the process window, identifying defects, and generating the initial dimensional report — T2 is a confirmation trial that runs the documented T1 process settings and measures whether the parts are within tolerance, the cycle time matches the quotation, and the mold operates reliably over a 50–200 shot run. If T1 found the process, T2 proves it.

Flash — Thin excess material that escapes between the mold parting line or around ejector pins. Cause: insufficient clamp force, worn parting line, excessive injection pressure, or contaminated mold surface. Flash thickness: 0.02–0.1mm. Requires secondary trimming to remove. See also related guide.

Key Facts

  • T2 typically runs 50–200 consecutive shots using the process parameters documented at T1. The goal is to verify process stability — part weight, dimensions, and cosmetic quality should remain consistent across the entire run.
  • The T2 dimensional report is the acceptance document. All critical dimensions must fall within the drawing tolerances, measured on parts from the stable middle portion of the run (shots 20–150), not from the first 10 warm-up shots.
  • If T2 fails on the same dimension that failed at T1, the mold modification between T1 and T2 did not fix the problem — and the root cause may be a process parameter, not a mold dimension.

    • Flash — Thin excess material that escapes between the mold parting line or around ejector pins. Cause: insufficient clamp force, worn parting line, excessive injection pressure, or contaminated mold surface. Flash thickness: 0.02–0.1mm. Requires secondary trimming to remove. The related guide covers adjacent topics.

    The T2 Checklist

    1

    Run the documented T1 process settings

    Load the process sheet from T1 — every parameter documented: melt temperature, mold temperature, injection speed, holding pressure, holding time, cooling time, back pressure, screw RPM. Do not adjust parameters during T2 unless a safety issue arises. The purpose is to verify repeatability, not to optimize further.

    2

    Record part weight every 10 shots

    Weigh every 10th part (or every shot if the scale is available). Plot weight vs shot number. The weight should stabilize within the first 15–20 shots and remain within ±0.5 % for the rest of the run. A drifting weight indicates a process instability — check-ring leak, melt-temperature drift, or moisture variation in the resin.

    3

    Full dimensional inspection on 5 parts from the stable zone

    Select 5 parts from shots 30–100 and measure all critical dimensions from the drawing. Compare against the T1 report — dimensions that shifted after the mold modification should now be within tolerance. Dimensions that were correct at T1 should still be correct.

    4

    Cosmetic inspection at production-intent conditions

    Inspect the parts under the specified lighting conditions (typically 1000 lux at 500 mm distance). Check for all cosmetic defects: splay, flow marks, weld lines in visible areas, ejector-pin witness marks on cosmetic surfaces, and any defect that was flagged at T1.

    5

    Verify cycle time against the quotation

    Measure the actual cycle time over 10 consecutive shots (mold close to mold close). Compare against the quoted cycle time. If the actual cycle time is more than 10 % above the quotation, the cost-per-part calculation is wrong and must be renegotiated before production starts.

    T2 vs T1 — What Changes

    Aspect T1 T2
    Purpose discover process window, identify defects verify corrections, prove repeatability
    Shot count 20–50 shots 50–200 shots
    Parameter adjustment frequent (finding the window) none (fixed from T1)
    Dimensional data initial report (baseline) acceptance report (final)
    Cycle time not critical (optimizing quality) measured and compared to quote
    Decision list of mold modifications needed accept, conditional accept, or reject

    When T2 Requires a T3

  • If T2 reveals a new defect that was not present at T1 — this happens when a mold modification (e.g., gate enlargement, vent addition) inadvertently introduces a different problem.
    The new defect requires another modification and a T3 to verify.
  • If the dimensional report shows dimensions that are borderline (within tolerance but at the extreme of the range) on multiple features, the mold may need fine-tuning — typically steel-safe adjustments to the cavity dimensions or gate size.
    A T3 confirms the fine-tuning.
  • If the cycle time at T2 is significantly above the quotation (more than 15 %) and the cause is a cooling or ejection issue that requires mold modification, a T3 is needed to verify the cycle-time improvement after the modification.
  • If the resin used at T2 is a substitute (not the production-intent grade), the dimensional results and process parameters may not be valid for the production resin.
    A T3 with the correct resin is required before the mold can be accepted.

    • Frequently Asked Questions

    Who should attend the T2 trial?

    The tooling engineer (or customer representative) should attend T2 in person or via video link.
    T2 is the acceptance trial — the person who will sign the acceptance document should see the parts being produced, the process running without adjustment, and the mold operating as designed. Remote attendance via a live video feed with a camera on the machine console and the part drop is acceptable if travel is not practical.

    What documents should be delivered after T2?

    The mold maker should deliver: the complete process parameter sheet (all machine settings), the dimensional inspection report with CMM data, a shot-weight log, a cosmetic inspection summary, the actual cycle time measurement, and a list of any open issues or conditional-acceptance items. These documents form the acceptance package.

    Can T2 samples be used for customer validation?

    Yes — T2 samples from the stable production zone (shots 20–150+) are suitable for customer validation if they were produced with the production-intent resin and the documented process parameters. Label them clearly as T2 samples with the date, machine ID, and shot numbers. Do not mix T2 samples with T1 samples or with production parts.

    Key Takeaways

    1. T2 is a verification trial, not an optimization trial. Run the documented T1 parameters without adjustment and measure the results. If the parameters need further tuning at T2, the T1 process development was incomplete.
    2. The T2 dimensional report is the acceptance document. It must be measured on parts from the stable zone of the run, not from warm-up shots, and it must cover all critical dimensions from the drawing.
    3. T2 acceptance has three outcomes: full acceptance (all dimensions in tolerance, all defects resolved), conditional acceptance (minor open items with a defined corrective action and timeline), or rejection (major issues requiring another modification cycle and T3).

    A T2 that produces 200 good parts with consistent weight, documented parameters, and a complete dimensional report is the end of the mold-development phase. A T2 that still requires parameter adjustments, produces inconsistent parts, or has unresolved dimensional failures is not a T2 — it is a continuation of T1, and the mold is not ready for production.

    Sources
    RJG — mold trial methodology
    Plastics Technology — process validation
    Beaumont Technologies — mold tryout best practices

    Sources: Plastics Technology · Plastics Technology Online · Society of Plastics Engineers (SPE) · ThomasNet