Blow Molding
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Uneven Wall Thickness of High-Density Polyethylene Blow Molded Products
Problembeschreibung
The wall thickness of various parts of the blow molded product differs greatly; the thin-walled parts have insufficient strength and are easy to break, while the thick-walled parts waste material.
Uneven wall thickness affects the service performance and appearance of the product and is common in bottle and barrel products.
Ursachenanalyse
（1）The parison wall thickness is uneven, and it sags and becomes thinner during parison extrusion
（2）The blow-up ratio is too large, causing uneven deformation of the parison
（3）The mold temperature is uneven, with differences in cooling rates at various parts
（4）The blowing air pressure is insufficient or uneven
（5）The parison control system (AWDS) is not enabled or is set improperly
Lösung
（1）Enable the parison wall thickness control system (AWDS) and set a reasonable wall thickness distribution curve
（2）Appropriately reduce the extrusion temperature to a reasonable value within the 180-260°C range to increase the melt strength and reduce sagging
（3）Optimize the blow-up ratio, generally controlled at 1.5-3.0
（4）Control the mold temperature to be uniform, with the temperature difference between parts not exceeding 5°C
（5）Adjust the blowing air pressure and blowing rate to ensure uniform inflation
Wichtigste Erkenntnis
Uneven wall thickness is caused by parison sagging and uneven inflation, and needs to be solved through parison control and process optimization.
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