Parting-line Flash: Guide for Avoiding

About the parting-line flash

1. Phenomenon of parting-line flash

A phenomenon in which the resin squeezes out and solidifies on the parting line of the mold.

2. Causes of parting-line flash

  • There is a gap in the mold
  • Foreign matter is attached between the mold plates
  • Rising internal pressure(insufficient vent)
  • High injection pressure
  • Insufficient mold clamping force
  • Large material supply
  • High resin temperature
  • Long injection pressure retention
  • Fast injection speed

3. Measures to avoid of parting-line flash

  • Eliminate mold gaps
  • Clean the mold
  • Attach a gas vent to the sprue and runners
  • Degas just below the sprue part and at the runner end.
  • Increase the air vent near the final filling part of the product part.
  • Lower injection pressure
  • Increase mold clamping force
  • Proper supply amount
  • Adjust the cylinder temperature to an appropriate temperature
  • Make the pressure holding time appropriate
  • Slow the injection speed
  • By increasing the number of vents, the internal pressure is reduced and burr is prevented.
  • By taking good venting measures with the mold, there is no air resistance in the mold and molding at low pressure is possible.

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