Injection Molding
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Flow marks in PU '2079851475616104452
Problem Phenomenon
Radial flow marks centered on the gate appear on the surface of PU injection molded products
Cause Analysis
Injection speed too fast causing unstable melt front; mold temperature too low <30°C, the front cools rapidly forming marks
Solution
1) Adopt multi-stage injection speed slow-fast-slow to control front stability; 2) Increase mold temperature to 40-50°C to delay front cooling; 3) Stabilize injection pressure to avoid fluctuation; 4) Increase gate area to reduce sudden pressure change at the gate
Key Takeaway
Flow marks are caused by unstable injection front and rapid cooling; multi-stage injection and high mold temperature are key
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