Plastic injection moulding: possible faults, causes and solutions

Problem of burnt spots on the injected part.

Possible causes may be:.

• Plugged gas leaks.
• Injection speed too high.
• Material temperature too high.

The solutions:

• Clean gas leaks.
• Reduce injection speed.         
• Reduction of the temperature of the material.

Problem of spontaneous burrs in the fitting areas.

Possible causes may be:.

• Foreign body in the partition line.
• Over-injection of the part.
• Material temperature too high.
• The machine does not have sufficient clamping force to compensate for the injection pressure.
• Control of mould cooling temperatures.

The solutions:

• Check the fitting areas for foreign matter or plastic residue from previous injection mouldings.
• Verification of partition surfaces to check for possible damage.
• Review of the injection process: speeds, temperatures, load and pressures.
• Regulation of the closing force of the machine.
• Check the cooling of the mould.

Continuous burrs in the adjustment areas.

Possible causes may be:.

• Wear of the adjustment areas.
• Foreign bodies or plastic debris deposited in the seals.
• Machine chucks out of adjustment.
• Misadjusted injection parameters: speeds, load and pressures.
• Material temperature too high.
• The solutions:

The solutions:

• Repair the fasteners and readjust the injection mould.
• Remove foreign bodies or plastic debris in the sealing area.
• Replacement or readjustment of locking plates.
• Review of the injection process: speeds, temperatures, load and pressures.
• Regulation of the closing force of the machine.
• Check the cooling of the mould.

Joining line in an undesired location.

Possible causes may be:.

• Temperature of plastic too low.
• The material entries section is different.
• Clogged injection points.
• Non-uniform heating of the hot chamber.
• Nozzles at different temperatures.
• Inequality of outgassing due to leakage.
• Lack of uniformity in cooling.

The solutions:

• Verification of injection temperatures.
• Check the condition of the injection nozzles.
• Check the operation of the shutters.
• Check the hot block resistors.
• Check for gas leaks.
• Check Mould cooling.