Injection Molding
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HDPE injection speed control
Problem Phenomenon
After high-speed injection the product is burnt near the gate, and at low speed flow marks and insufficient filling appear
Cause Analysis
HDPE has good fluidity, but high-speed injection produces shear stress and molecular orientation, leading to uneven shrinkage; at low speed the front cools down and forms flow marks; medium-speed balance is the standard strategy
Solution
①Control the injection speed at medium speed; ②appropriately reduce the speed in the gate area to prevent shear; ③increase the melt temperature to compensate when flow marks appear; after adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability
Key Takeaway
HDPE speed strategy is based on medium speed; the balance between shear and flow marks is achieved by a segmented speed curve; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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