Mold Commissioning Checklist — What Must You Verify When a New Mold Arrives at Your Facility, and How Do You Confirm It Runs on Your Machines?

Last updated: 2026-09-04 · Reading time: about 6 min

Commissioning is what happens after the mold leaves the mold maker’s dock: it arrives at your plant, goes on your press, runs with your resin and your auxiliary equipment, and has to prove it holds spec in your environment. The mold passed at the mold maker’s — but commissioning introduces new variables (machine tonnage, screw size, water quality, ambient conditions), and the gaps between the two environments are where most delays appear.
See also related article.

Key facts

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  • Commissioning is not the mold trial. The trial proves the mold works at the mold maker’s facility; commissioning proves it works at yours — on your press, with your resin lot, your temperature control units, your dryers and your operators.
  • The checklist has four gates: receiving inspection (shipping damage and accessories), machine setup (platen, tie bars, water, hot runner), short-shot validation (flow pattern at reduced fill) and production trial (continuous run with documented acceptance criteria).
  • What fails at commissioning usually did not show at the mold maker’s: machine size differences, resin lot shifts, thermal equilibrium not reached, ejector pins stuck from shipping moisture, or hot runner seals dented in transit. The receiving inspection catches most of these before they become delays.

    • Cycle time — The total time for one injection molding cycle: injection + packing + cooling + mold open/close + ejection. Typical range: 15–60 seconds. Cycle time determines production rate and cost per part — reducing cycle by 5 seconds saves 10–15% annual production cost. See also related guide.

    What are the four commissioning gates — and what must each one prove?

    Each gate has a pass condition. Nothing moves to the next gate until the previous one is signed off — skipping a gate is how a two-day setup becomes a two-week delay.

    1. Receiving inspection. Open the crate within 24 hours — delay may void damage claims. Check for impact marks, verify rust preventive, confirm accessories against the shipping list (spare parts, tools, CMM reports, trial video, DFM report). Measure mold weight vs shipping documents — a difference signals a missing component. Move every ejector pin by hand.
    2. Machine setup. Verify press clamp force exceeds projected area times cavity pressure. Confirm mold height fits tie bars, weight suits the platen, locating ring matches machine center. Connect water lines, leak-test at 1.5× operating pressure. For hot runner molds: check thermocouple and heater resistance, insulation above 10 MΩ. Dry-cycle to confirm ejector stroke and mold protection.
    3. Short-shot validation. Fill the cavity to roughly 95% with reduced packing pressure, using the production resin lot. The flow pattern shows gate balance, weld line locations and whether vents the last-to-fill areas. If flow is uneven, weld lines are in the wrong place or air traps are at the last fill, the mold needs modification before proceeding — no amount of parameter tuning fixes a flow-path problem.
    4. Production trial. Run continuously for a documented shot count — typically a few hundred to a few thousand depending on the program. Record cycle time, part weight at intervals, and visual defects. Measure parts at three stages: the first shots (setup validation), the middle (process stability), and the last shots (endurance and ejector condition). Acceptance criteria are set before the run: cycle time within a documented band, part weight stable, Cpk above the program’s threshold on critical dimensions.

    Mold commissioning. The on-site process of installing a new mold at the production facility, running it on the production press with the production resin, and documenting that it holds specification continuously — as distinct from the mold trial, which takes place at the mold maker’s facility on their machines.

    What fails at commissioning that did not show at the mold maker’s trial?

    The mold passed at the mold maker’s — so the failures at commissioning are almost always environmental, not design failures. The five recurring modes:

  • Cycle time exceeds target. The production press is smaller than the mold maker’s press, so plasticizing rate is lower and recovery takes longer. Prevention: confirm at the mold maker’s trial that the mold runs on a press equal to or smaller than the production press — not a larger one.
  • Dimensions drift after a few hundred shots. The mold has not reached thermal equilibrium — steel expands as it heats, cavity dimensions shift. Prevention: run the mold at production cycle for long enough to steady-state temperature before measuring; confirm with the mold temperature sensor.
  • Ejector pins stick or break. Insufficient bore clearance, combined with moisture exposure during shipping, causes corrosion in the bore. Prevention: rust preventive before shipping, hand-check every pin at receiving.
  • Color mismatch with approved samples. The mold maker’s trial used a different resin lot — MFI and colorant differ slightly. Prevention: reserve the production resin lot before the mold is built and use the same lot for both trials.
  • Hot runner leaks at the nozzle. The nozzle tip seal was dented in transit — the leak appears only at full packing pressure. Prevention: pressure-test the hot runner at receiving at 1.5× operating pressure and hold.

    • Every one of these is catchable at receiving or at the short-shot stage — the cost of catching them early is a day of inspection; the cost of catching them after the production trial has started is a mold return, rework and weeks of delay.

    What is the mold maker’s role during commissioning — and who pays for what?

    For complex molds — multi-cavity, hot runner, stack — the mold maker typically sends a technician on-site for several days to support setup, adjust parameters and troubleshoot. For simpler molds, the production team commissions independently with remote video support.

    The contract should state clearly: the mold maker’s warranty covers failures caused by mold defects. It does not cover failures caused by the production setup. If your program needs the mold maker to attend, agree scope and duration before the deposit.

    “Commissioning is where the mold meets reality. The mold maker proved it on their press; we have to prove it on ours. The checklist is not a formality — it is the only thing standing between a mold that ran beautifully last week and a mold that will not run today because the water quality is different or the press is two sizes smaller.”

    — Process Engineer, aCatMould

    Frequently asked questions

    How long does commissioning take — and what extends it?

    A straightforward commissioning runs a few days to a week: receiving (1 day), machine setup (1–2 days), short-shot (half day to 1 day), production trial (1–3 days), report (1 day).

    What extends it is a failure that sends the mold back for modification — weeks of rework, shipping and re-commissioning. The receiving inspection and short-shot gate catch those failures early.

    Can the same mold be commissioned at more than one facility?

    Yes — each facility runs a full commissioning, because press, auxiliary, water quality, ambient conditions and operators all differ. A mold that runs cleanly on one press may need adjustments on another.

    Plan for it: the mold maker’s trial should run on a press equal to or smaller than the smallest production press, so the process window is conservative from the start.

    What documentation should come out of commissioning?

    A commissioning report signed by process, quality and production. It includes: receiving record, machine settings, short-shot photos, production trial data (cycle time, weight log, Cpk), defect rate and deviations. If your program needs a documented weight and flatness result, tell us before the deposit and we will say plainly which commissioning data we deliver.

    Key takeaways

    1. Commissioning is the on-site proof that the mold runs at your facility — distinct from the mold trial at the mold maker’s.
    2. Four gates, none skippable: receiving, machine setup, short-shot, production trial — each with a documented pass condition.
    3. What fails at commissioning is almost always environmental, not design — and almost all of it is catchable at receiving or short-shot if you look.

    Mold commissioning is not a repeat of the mold trial — it is a different test in a different environment. The mold proved itself at the mold maker’s; commissioning proves it at yours. The checklist is short, the gates are clear, and skipping one always costs more than running it. At aCatMould we commission every mold on the production press with the production resin, document the four gates, and hand you the report that shows the mold ran before we signed it off.

    Sources
    Plastics Technology — mold installation, startup and process validation
    Society of Plastics Engineers — mold acceptance and commissioning practice
    Plastics Industry Association — processing guidelines and mold setup
    Autodesk Moldflow — simulated fill and process window for mold trials
    MatWeb — resin grade properties and lot-to-lot variation reference

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