Injection Molding
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Flow Marks and Ripples on the Surface of PE Injection Molded Products
Problem Phenomenon
Ripple-like flow marks or concentric-circle ripples around the gate appear on the surface of PE products, obvious on high-gloss surfaces.
Cause Analysis
The melt front temperature drops too fast or the advance speed is unstable, leaving ripples on the cavity surface; low mold temperature, unreasonable injection speed profile, and too small gate all cause front instability.
Solution
①Optimize the injection speed profile to keep the front stable; ②Appropriately increase mold temperature and melt temperature; ③Enlarge the gate to reduce throttling; ④Check the temperature uniformity of the hot runner; ⑤Adjust the gate position to improve the flow state if necessary.
Key Takeaway
PE flow marks and ripples = a 'front management' problem: stabilize speed, maintain temperature, and enlarge the gate — the three axes; what it reflects is filling stability, which cannot be covered up by surface treatment.
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