Blow Molding
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PE '2079851475616104457 Parison Sag
Fenómeno do problema
In extrusion '2079851475616104457, the parison is thin at the top and thick at the bottom, the product wall thickness is out of control, and the upper part of the bottle is too thin with insufficient strength.
Análise das causas
The parison is stretched and sags under its own weight; insufficient melt strength or excessive melt temperature aggravates the sagging; the longer the parison and the slower the extrusion, the longer the suspension time and the more obvious the sagging.
Solução
①Appropriately reduce the melt temperature to increase the melt strength; ②increase the extrusion speed to shorten the parison suspension time; ③use parison wall thickness program control (axial multi-point thickness adjustment) to compensate for the sagging; ④select high melt strength grades; ⑤optimize the mold pinch-off and blowing timing.
Conclusão principal
PE parison sag is jointly controlled by 'temperature reduction + speed increase + programmed wall thickness': melt strength is fundamental, and programmed wall thickness is the compensation means; the longer the parison, the more the wall thickness program must 'pre-compensate' the sagging.
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