Blow Molding
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Bottom material pinching/flash of general-purpose polyethylene blow molded products
Problem Phenomenon
Flash or material pinching marks appear at the bottom of the blow molded product, requiring trimming.
Bottom flash affects the appearance, and improper trimming leads to leakage.
Cause Analysis
（1）The parison length is too long, and there is much excess material at the bottom
（2）The mold pinch-off is improperly designed or worn
（3）The mold clamping force is insufficient, and the bottom sealing is poor
（4）The parison wall thickness is too thick
（5）The mold temperature is low, and the material cutting is not clean
Solution
（1）Adjust the parison length to reduce the bottom excess material
（2）Check the mold pinch-off, and repair it if worn
（3）Appropriately increase the mold clamping force
（4）Adjust the parison wall thickness to a suitable value
（5）Appropriately raise the mold bottom temperature to a reasonable value within the range of 30-80°C
Key Takeaway
Bottom flash is caused by excessive parison length or pinch-off problems, and the parison length needs to be adjusted and the pinch-off maintained.
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