Molding Defects


Normal Flash


Excess molding material that penetrates into mold gaps (i.e., between parting faces, slide push-out faces, and inserts, etc.) in a molten state.

Molding Machine Conditions
Die Conditions
Material Conditions
  • Insufficient mold clamping pressure in the molding machine
  • Aging of the die
  • Insufficient mold clamping pressure
  • Insufficient precision at the die's mating faces
  • The molded product is arranged in a cantilever-type setup as a result of die design
  • Plastic has low viscosity

If there is insufficient clamping pressure, estimate the correct pressure using the following equation and choose an appropriate molding machine.


Die clamping pressure = Projected surface area x die-internal effective injection pressure / 1,000 kg

In the case of ABS, a rough value for 400 kg/cm2 can be used in this calculation for the die-internal effective injection pressure

  • Switch to a suitable molding machine.
  • If the problem is related to mating faces, a joint examination must be carried out with the die machining company.
If the problem is related to the plastic's viscosity, either lower the temperature of the plastic or switch to a grade with higher flowability.


 UMG ABS Ltd. accepts no responsibility for the quality or safety of any customer products which use our materials or which have made use of any type of data provided by this company.
 Customers are requested to independently determine the suitability of our materials for their products. We also request that sufficient attention also be paid to laws, regulations, and industrial rights.

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