Blow Molding
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Uneven wall thickness of general-purpose polyethylene blow molded products
Fenómeno del problema
The wall thickness of each part of the blow molded product differs greatly, the thin-walled part has insufficient strength and is easy to break, and the thick-walled part wastes material.
Uneven wall thickness affects the use performance and appearance of the product, and is common in bottle and barrel products.
Análisis de la causa
（1）The parison wall thickness is uneven, and the parison sags and becomes thinner during extrusion
（2）The blow-up ratio is too large, resulting in uneven parison deformation
（3）The mold temperature is uneven, and the cooling rates of each part differ
（4）The blowing air pressure is insufficient or uneven
（5）The parison control system (AWDS) is not enabled or is improperly set
Solución
（1）Enable the parison wall thickness control system (AWDS) and set a reasonable wall thickness distribution curve
（2）Appropriately lower the extrusion temperature to a reasonable value within the range of 160-260°C to increase the melt strength and reduce sag
（3）Optimize the blow-up ratio, generally controlled at 1.5-3.0
（4）Control the mold temperature uniformly, and the temperature difference between each part should not exceed 5°C
（5）Adjust the blowing air pressure and blowing rate to ensure uniform inflation
Conclusión clave
Uneven wall thickness is caused by parison sag and uneven inflation, and needs to be solved through parison control and process optimization.
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