Blow Molding
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Excessively Thin Wall Thickness at the Mold Parting Line of Polypropylene Blow-Molded Products
Problem Phenomenon
The wall thickness of the blow-molded product near the mold parting line is obviously too thin, the strength is low, and it is easy to crack from here.
The thin wall at the parting line affects the sealability and pressure resistance of the product.
Cause Analysis
(1) The parison is squeezed too much at the parting line
(2) The blow-up ratio is too large, and the blowing at the parting line is the most severe
(3) The venting at the mold parting line is poor, and the melt does not adhere tightly
(4) The parison position is offset and is not at the center of the mold
(5) The blowing pressure is too large, and the parting line is over-stretched
Solution
(1) Adjust the parison wall thickness distribution, and appropriately thicken near the parting line
(2) Optimize the blow-up ratio to avoid being too large
(3) Set vent grooves or vent holes at the mold parting line
(4) Adjust the parison position to ensure it is at the exact center of the mold
(5) Appropriately reduce the blowing pressure and blow in stages
Key Takeaway
The thin wall at the parting line is caused by parison squeezing or uneven blowing, and the parison wall thickness distribution and blowing process need to be optimized.
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