Trouble Shooting

Molding Defects

Flash

The terms "flash", "fins", and "spew" are used to refer to excess molding material that penetrates into mold gaps (i.e., between parting faces, slide push-out faces, and inserts, etc.) in a molten state.

Appearance
Characteristics	Normal	Flash

Cause / Countermeasures

Characteristics	Excess molding material that penetrates into mold gaps (i.e., between parting faces, slide push-out faces, and inserts, etc.) in a molten state.
Cause	Molding Machine Conditions	Die Conditions	Material Conditions
Cause	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	Low nozzle and cylinder temperatures Excessive metal cooling - Entry of air into the cylinder Plastic has low viscosity
Countermeasures	If the mold clamping force is insufficient, use the following formula to roughly estimate the mold clamping pressure and select a molding machine. Mold clamping pressure = projected area x effective injection pressure in the mold/1000kg In the case of ABS resin, the effective injection pressure in the mold is approximately 400 kg/cm2.	Examine the die 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.

Appearance
Characteristics	Normal

Appearance
Characteristics	Flash

Cause / Countermeasures

Characteristics	Excess molding material that penetrates into mold gaps (i.e., between parting faces, slide push-out faces, and inserts, etc.) in a molten state.
Cause	Molding Machine Conditions	Die Conditions	Material Conditions
Cause	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	Low nozzle and cylinder temperatures Excessive metal cooling - Entry of air into the cylinder Plastic has low viscosity
Countermeasures	If the mold clamping force is insufficient, use the following formula to roughly estimate the mold clamping pressure and select a molding machine. Mold clamping pressure = projected area x effective injection pressure in the mold/1000kg In the case of ABS resin, the effective injection pressure in the mold is approximately 400 kg/cm2.	Examine the die 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.

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Silver streaks Short shot Jetting Flow marks Color streaks Weld lines Flash Delamination Stringiness Sink Marks Warping or Twisting

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