Injection Molding
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PVC Injection Speed Medium-Low Speed
Problem Phenomenon
After increasing injection speed, products were burnt near the gate; after reducing speed, weld lines appeared
Cause Analysis
PVC is shear-sensitive, and shear heat from high-speed injection locally degrades the gate area; but reducing speed too much cools the melt front, and weld lines and flow marks appear again—the window requires fine balance
Solution
①Injection speed 50-80mm/s medium-low speed; ②pass the gate area at low speed then speed up in the later stage; ③compensate weld lines with temperature and gate position; after adjustment, continuously sample to verify the effect, and resume mass production after confirming stability
Key Takeaway
PVC speed strategy is segmented control dominated by medium-low speed; slow at the gate area, stable in the filling section, temperature compensates weld lines; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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