Last updated: 2026-09-02 · 5 min read

Injection Mold Maintenance Schedule — What Should Be Inspected Daily, Weekly and by Shot Count?

Mold maintenance follows a tiered schedule: daily checks (visual inspection, cleaning parting line, checking ejector return), weekly checks (lubricating guide pins and slides, inspecting vents), and shot-based maintenance (disassembly and inspection at 50,000, 100,000 and 250,000 shot intervals) — the schedule is determined by the mold’s complexity, the resin being molded and the operating environment. A documented maintenance schedule extends mold life by 2–3× and prevents unplanned downtime from progressive wear that goes undetected until it causes a production defect.

Cavity — The hollow space inside the mold that forms the part shape. Multi-cavity molds produce multiple parts per shot. Cavity count determines production output but also mold cost and complexity. Each cavity must be balanced for uniform fill. See also related guide.

Key Facts

  • Daily maintenance takes 5–10 minutes per mold: clean the parting line, inspect ejector pins for return, check cooling connections for leaks and apply rust inhibitor if the mold will be idle for more than one shift.
  • Weekly maintenance takes 20–30 minutes: lubricate guide pins, leader pins and slides; inspect vents for blockage; check spring pressure on ejector return; and document any changes in part quality that indicate wear.
  • Shot-based maintenance is the most important: at 50,000 shots, inspect for initial wear; at 100,000, disassemble and inspect all wearing components; at 250,000, replace wearing components (ejector pins, guide bushings, spring sets) before they fail.

    • Cavity — The hollow space inside the mold that forms the part shape. Multi-cavity molds produce multiple parts per shot. Cavity count determines production output but also mold cost and complexity. Each cavity must be balanced for uniform fill. The related guide covers adjacent topics.

    Maintenance Schedule by Interval

    Interval Tasks Time
    Daily (every shift) Clean parting line; inspect ejector return; check cooling connections; apply rust inhibitor if idle 5–10 min
    Weekly Lubricate guide pins and slides; inspect vents; check ejector springs; document part quality changes 20–30 min
    50,000 shots Visual inspection for initial wear on parting line, gates and ejector components 30–60 min
    100,000 shots Disassemble; inspect all wearing components; measure ejector pin clearance; check cooling channel deposits 2–4 hours
    250,000 shots Replace wearing components (ejector pins, guide bushings, springs); re-polish cavity surfaces if needed 4–8 hours

    What Accelerates Mold Wear

  • Abrasive resins: glass-filled, mineral-filled and flame-retardant resins accelerate wear on gates, ejector pins and cavity surfaces. Molds running abrasive resins need shot-based maintenance at 50% of the standard interval (e.g., 50,000 instead of 100,000).
  • Corrosive resins: PVC, flame-retardant grades and some engineering resins release corrosive byproducts during molding that attack mold steel. Molds running corrosive resins require stainless steel cavities or protective coatings, plus more frequent cleaning.
  • High cycle rates: molds running 24/7 accumulate shots faster and need maintenance more frequently — the schedule should be based on shot count, not calendar time.

    • What This Means for Your Quotation

    The quotation should include a maintenance schedule document — specifying the daily, weekly and shot-based tasks, the responsible party (molder or mold owner) and the cost of replacement components. When the maintenance schedule is documented and agreed, the mold life is predictable; when it is not documented, the mold runs until something breaks, and the downtime cost far exceeds the maintenance cost.

    Frequently Asked Questions

    Who is responsible for mold maintenance?

    If the mold maker also runs production, the mold maker is responsible for maintenance. If the mold is shipped to the buyer’s facility, the buyer is responsible — but the mold maker should provide the maintenance schedule and recommend spare parts. The purchase order should specify who is responsible for each maintenance level (daily, weekly, shot-based) and who pays for replacement components.

    How do you know when a mold needs maintenance?

    The indicators are progressive: increased flash (parting line wear), short shots (gate or vent blockage), ejector pin marks (pin wear or binding), dimensional drift (cavity wear), and surface defects (corrosion or deposit buildup). If any of these appear, the mold needs inspection — waiting until production is affected wastes material and delays the program.

    What spare parts should be kept on hand?

    The minimum spare parts inventory includes: ejector pins (2× the number in the mold), guide bushings, spring sets, cooling fittings and O-rings. For molds with hot runners, spare heater bands and nozzle tips should be on hand. The mold maker’s quotation should include a spare parts list with part numbers and recommended quantities.

    Key Takeaways

    1. Mold maintenance follows three tiers: daily (5–10 min, clean and inspect), weekly (20–30 min, lubricate and document), and shot-based (50K/100K/250K intervals, disassemble and replace wearing components).
    2. Abrasive and corrosive resins accelerate wear — molds running these materials need maintenance at 50% of the standard interval, with stainless steel or coated cavities for corrosion resistance.
    3. The quotation should include a maintenance schedule document specifying tasks, responsible party and spare parts — so the mold life is predictable and maintenance cost is planned, not reactive.

    Send aCatMould the mold specifications and production resin, and the quotation includes a maintenance schedule — daily, weekly and shot-based tasks with responsible party and spare parts list — so the mold life is managed proactively, not reactively.

    Sources
    MoldMaking Technology — mold maintenance best practices
    Plastics Technology — mold maintenance scheduling
    SPE — mold maintenance guidelines and spare parts management

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