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Causes and solutions of dimensional difference of injection molded parts
- Sep 28, 2018 -

Description: Changes in weight and size during injection molding exceed the production capacity of the mold/injection machine/plastic combination.

Possible causes and recommended remedies:

1. injection molding machine

A, the plastic in the input cylinder is uneven.

Check whether there is sufficient cooling water through the hopper throat to maintain the correct temperature.

B, the temperature or fluctuation range of the ejection cylinder is too large.

Check if there are any faulty or loose thermocouples.

Check whether thermoelectric thermocouples used with the temperature controller belong to the correct type.

C, injection molding machine capacity is too small.

Check the injection volume and plasticizing capacity of the injection molding machine, and then compare with the actual injection volume and the amount of plastics per hour.

D, unstable injection pressure.

Check whether there is a stable melting pad for each operation.

Check whether the backflow prevention valve is leaking and replace it if necessary.

Check for incorrect feeding settings.

E, screw reduction instability.

It is guaranteed that the screw is reset at every operation, that is, no more than 0.4mm (0.16in).

F, operation time and viscosity of the melt are inconsistent.

Check the inconsistency of operation time.

Use back pressure.

2. mold

A and gate parts are blocked.

Check if there is any indication that the gate residue is in the hole of the gate, especially the submerged gate.

B, inconsistent mold temperature control.

Check whether the cooling medium used for mold cooling is temperature dependent.

Check whether there is any blockage in the cooling pipe of the mould.

Check whether the cooling pipe is connected properly.

3. plastic

A, plastic change.

Check the change of feed volume. Ensure that the fine ends are screened out from the recycled materials.

Check whether the two batches of plastic are mixed together.