TROUBLESHOOTING WELD LINES / FLOW MARKS IN INJECTION MOLDING

 WELD LINES AND FLOW MARKS


MAJOR CAUSES FOR THE DEFECT :


  • Molten plastic material is too cold in the mold after injection.
  • when there is an excessive mold lubricant in the mold.
  • Mold is too cold .
  • Injection speed is slow.
  • Low injection pressure.
  • Volatile gas are been trapped in the mold.
  • Air unable to escape from the mold as fast as it should. 

        TROUBLE SHOOTING :

  • Increase injection pressure.
  • Increase injection speed.
  • Increase plasticizing capacity of machine if possible.

TEMPERATURE :

  • Increase Barrel / Cylinder temperature.
  • Increase Nozzle temperature.
  • Increase Mold Temperature.
  • Make proper/even/balanced cooling system for the mold.
MOLD :

  • Add proper vent on the mold.
  • Increase the runner system in the feed channel.
  • Increase the gate system.
  • Increase the opening of sprue.
  • Make necessary adjustment for the mold adjustment.
  • Thick the particular area where the welded part is too thin.
  • Filling rate of the material in the mold should be equal.
  • Increase the opening of nozzle.
  • If the gate is too far from the weld one can add another substitute gate.
  • Make necessary changes if wall thickness is too thin it will cause premature freezing.
  • Check the core shifting if it has been done then make proper changes over there.
MATERIALS : 

  • Purify or clean the material because contaminated material can cause proper knitting of the material.
  • Lubricate the material to make the material flow easily in the mold. 

 

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