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Notes on injection moulding: part design, tooling and cost

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How should an injection mould be stored between runs, and shipped to another plant?

Before storage, clean the mould and check it for wear, then blow out and dry every water line. Apply a rust preventive only once the steel is dry, close and strap the mould, and store it somewhere dry with a steady temperature. For shipping, add a locked mould strap, a strong crate with the mould blocked to the base, rated lashing and a document pack. Stoner, a maker of mould care products, lists surface rust, corrosion inside water lines and trapped moisture among the most common preventable causes of start-up defects after storage.

Storage routine between runs

  1. Maintenance check. Paulson Training's checklist starts with inspecting cavities, gates and runners for wear; checking for broken ejector, guide and return pins; and checking slides, cams and the sprue bushing.
  2. Clean. Stoner notes that residue such as release agent or plastic left on the steel can trap moisture and speed corrosion, so clean parting lines, corners and recesses.
  3. Drain and dry water lines. Both Stoner and Slide Products single out cooling circuits: standing water in channels drives internal corrosion. Blow lines out and cap them.
  4. Dry before protecting. Stoner warns that rust preventive applied over damp steel traps moisture underneath.
  5. Choose protection for the storage time. Stoner suggests lighter coatings for days or weeks, and heavier rust preventive plus desiccant or vapour corrosion inhibitor packaging for months.
  6. Avoid condensation. Slide Products notes that moving a warm mould into a cold room can cause condensation, and advises keeping the mould above the room's dew point in a climate-controlled area or with a dehumidifier.
  7. Grease moving parts. Slide Products recommends retracting slides and greasing slides, lifters and leader pins.
  8. Record its state. Note the last resin run, repairs, products applied and storage location to speed up restart.
  9. Safety check before moving it. Paulson lists checking the eyebolt, eyebolt threads and mould strap for damage.

Preparing a mould for shipment

The published multimodal mould transport procedure from OPmobility (formerly Plastic Omnium) gives a detailed model. Among its points:

  • Keep the halves locked. Paulson notes many moulds use a lock strap or latch so the halves cannot open in handling.
  • Crate it properly. The procedure requires a heavy crate with ISPM 15 certification, with anti-slip mats under the mould and under the crate, a vacuum foil sheet, the mould blocked to the base with screws, and a wooden frame so the crate does not collapse under lashing. It is closed with screws only, to make customs inspection easier.
  • Centre the load. The mould's centre of gravity should be as low as possible and centred in the container.
  • Use rated lashing. Strap strength must be marked on the strap so it can be checked in transit.
  • Declare weight. The procedure notes that since 1 July 2016 shippers must declare the verified gross mass of a loaded container before it goes on a ship.
  • Brief the carrier. It warns of a very high risk of the load shifting or tipping, and says securing should not be changed in transit without the sender's agreement.

What should travel with a transferred mould

  • mould drawings, a parts list and spare parts
  • hot runner wiring and controller settings, if fitted
  • the last approved process sheet and a set of last-shot parts
  • a maintenance history and the asset tag details, with photographs (see who owns the mould)

Summary of published maintenance guides and one corporate transport procedure. Always follow your plant's lifting and transport rules and your carrier's requirements.

Questions buyers ask

Will a mould be ready to run as soon as it arrives?

Plan a trial. Different presses, water and controllers usually need some process adjustment, and the receiving plant may need a partial first article or PPAP resubmission.

How should a mould be lifted?

Only by its designed lifting points, with rated eyebolts and equipment, following plant procedures. Paulson advises carrying a mould close to the ground.

Who pays if it is damaged in transit?

That depends on your agreement and insurance. The OPmobility procedure includes a section on insurance for this reason.

Can I store a mould at my own premises?

Yes, if the storage is dry and temperature-stable and the mould was cleaned, dried and protected first.

Sources