Injection Molding
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Stress Whitening Appearing at the Ejector Pin Position of general purpose polystyrene Injection Molded Products
Problem Phenomenon
Stress whitening appears at the ejector pin position of the product, affecting the product appearance and service performance.
This problem often occurs in general purpose polystyrene '2079851475616104452 and needs to be solved in time.
Cause Analysis
（1）The processing temperature is set improperly (180-240°C range), resulting in unstable melt quality
（2）The general purpose polystyrene material characteristics (high transparency, high brittleness, good rigidity) are sensitive to this defect
（3）The mold design or condition is poor, affecting the molding quality
（4）The process parameters (injection speed, holding pressure, etc.) are set unreasonably
（5）Improper raw material pretreatment or regrind use problems
Solution
（1）First check and optimize the barrel temperature to ensure a reasonable setting within the 180-240°C range
（2）Adjust the injection speed and holding pressure; the recommended holding pressure of general purpose polystyrene is 80-120MPa
（3）Check the mold temperature (40-80°C range) and the venting condition
（4）Ensure the raw material is fully dried (70-80°C, 3-4h)
（5）Control the regrind ratio to no more than 15-20%, and regularly check the equipment status
Key Takeaway
This problem needs to be systematically solved from three aspects: material characteristics, process parameters, and mold conditions.
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