【Injection molding knowledge】TPE material common shrinkage water marks and other phenomena processing methods

  • Time of issue:2021-10-22
  • Views:970

【Injection molding knowledge】TPE material common shrinkage water marks and other phenomena processing methods

  • Categories:Industry News
  • Author:SPP
  • Origin:www.sptpe.cn
  • Time of issue:2021-10-22
  • Views:970

 TPE product shrinkage refers to the phenomenon that the surface raw materials at the wall thickness are pulled in due to volume shrinkage during the cooling and hardening process of the product, which results in the appearance of depression marks on the product surface.

  TPE shrinkage phenomenon usually has the following reasons.

  1 injection molding process problems (such as low injection pressure, insufficient holding time, high mold temperature, insufficient cooling time, etc.)

  2 structural design problems (uneven thickness of the glue bit, improper ratio of rib width to glue bit thickness, too thick glue bit thickness of the product, etc.)

  3 mold processing problems (feed opening too small or runner cross-section too small, etc.)

  4. Material aspect (shrinkage difference).

  TPE shrinkage solutions:

  1, increase the injection pressure, holding pressure, and extend the injection time. For tpe plastic with high fluidity, high pressure will produce flying edge and cause collapse pit, it should be adapted to reduce the material temperature, lower the barrel front section and nozzle temperature, so that the change of melt volume into the cavity is reduced and easy to cold solidify; for high viscosity plastic, the barrel temperature should be increased to make the mold filling easy. When shrinkage occurs in the gate area, the holding time should be extended.

  2, Increase the injection speed to make the part filled and eliminate most of the shrinkage.

  3, Thin-walled parts should increase the mold temperature to ensure smooth material flow; thick-walled parts should reduce the mold to speed up the curing of the skin to set.

  4, appropriately increase the cooling time to reduce thermal shrinkage. Extend the cooling residence time of the parts in the mold, maintain a uniform production cycle, increase the back pressure, the front section of the screw to retain a certain buffer pad, etc. are conducive to reducing shrinkage phenomenon.

  5, low precision products should be released from the mold early to let it cool slowly in the air or hot water, which can make the shrinkage depression smooth and does not affect the use.

  6, the temperature is too high or too low, will not be able to achieve the effect of pressure-holding.

  7, the amount of rubber injection is not enough, increase the amount of injection glue.
 

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