Injection Molding
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PC melt fracture phenomenon
Problem Phenomenon
Sharkskin-like rough texture appears on the product surface, especially near the gate, with uneven gloss
Cause Analysis
When the melt passes through the gate, shear stress exceeds the critical value and the surface melt fractures; PC high-molecular-weight grades have high elasticity and are more prone to it, and low-temperature high-speed injection further aggravates it
Solution
①Increase melt and mold temperature to reduce melt strength; ②Reduce injection speed in the gate area; ③Enlarge the gate cross-section, with the gate short and thick and polished；After adjustment, take continuous samples to verify the effect, and resume mass production only after confirming stability
Key Takeaway
Melt fracture is a typical shear defect of PC high-elasticity melt; raising temperature, reducing speed, and enlarging the gate are tried in order of cost；After confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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