Common Injection Molding Defects:
Insufficient Filling
Flash
Air Pockets
Warping
Silver Streaks
Surface Dullness
Weld Lines
Air Bubbles
Black Streaks and Burn Marks
Cracking
Ejection Overflow
Bending
Ejection Failure
Ejection Failure at the Gate
Material Overlapping Defects
Analysis and Solutions for Defects:
Insufficient Filling
The molded part’s volume is too large.
The runner or gate is too small.
Nozzle temperature is low.
Material temperature or injection pressure is low.
Fluid flow distance in the cavity is too long.
Mold temperature is low.
Injection speed is slow.
Insufficient material supply.
Poor ventilation.
Flash
Insufficient clamping force.
Poor mold design.
Impurities on mold surfaces.
Molded part’s projected area is too large.
Material temperature is too high.
Excessive material supply.
High injection pressure.
Air Pockets
Small runner or gate.
Large wall thickness variation in the molded part.
High material temperature.
Long flow distance from the gate.
Premature demolding.
Low injection pressure.
Short cooling time.
Insufficient holding pressure.
Warping
Poor material flow.
Low mold temperature.
Small sprue.
Silver Streaks
Moisture or volatile components.
Excessively high material temperature.
Low mold temperature.
Poor ventilation.
Poor design of molded part or mold.
Moisture or volatile components on the mold surface.
Contamination with impurities.
Improper screw operation.
Surface Dullness
Excessive lubricant or volatile components.
Excessive release agent.
Weld Lines
Material temperature.
Improper gate design.
Excessive volatile components or release agent in the material.
Rapid solidification of the material.
Poor design of the molded part.
Air Bubbles
Small runner or gate.
Low injection pressure.
Excessive moisture.
Poor molded part design.
Poor ventilation.
Black Streaks and Burn Marks
Material overheating.
Poor molding machine.
Poor mold design (small gate, poor ventilation).
Cracking
Excessive injection pressure.
Poor material flow.
Pushing pins in thick areas.
Poor ventilation.
Poor adjustment of holding pressure.
Large thermal stress.
Chemical corrosion.
Ejection Overflow
Improper gate design.
High injection speed.
Low material temperature.
Low mold temperature.
Bending
Insufficient cooling.
Ejection failure at the gate.
Uneven cooling.
Inappropriate injection pressure.
Improper gate position.
Core misalignment.
Uneven flow distance from the gate.
Ejection Failure
High injection pressure.
Poor mold temperature adjustment.
Poor mold design, inadequate ventilation.
Ejection Failure at the Gate
Poor mold installation.
Poor gate shape.
Material Overlapping Defects
Poor material feeding.
Excessive inclusion of crushed recycled materials.
Excessive external lubricant.
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