Blow Molding
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Blow-Out/Blow-Crack of Polypropylene Blow-Molded Products
Problem Phenomenon
The parison is blown out during '2079851475616104457, and holes or cracks appear in the product.
Blow-out leads to product scrapping, and is usually caused by excessive blowing pressure or parison quality problems.
Cause Analysis
(1) The blowing pressure is too large, exceeding the bearing capacity of the parison
(2) The parison wall thickness is uneven, and the thin-wall part is blown out first
(3) The parison temperature is too low, and the ductility is poor
(4) The blowing speed is too fast, and the parison has no time to deform uniformly
(5) There are impurities or bubbles in the parison as weak points
Solution
(1) Appropriately reduce the blowing pressure to 0.3-0.6MPa
(2) Enable parison wall thickness control to ensure uniform wall thickness
(3) Appropriately increase the extrusion temperature to a reasonable value within the range of 200-280°C
(4) Adopt a staged blowing method of pre-blowing + high-pressure blowing
(5) Check the cleanliness of the raw material and remove impurities
Key Takeaway
Blow-out is caused by excessive blowing pressure or poor parison quality, and the blowing process and parison quality need to be optimized.
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