Key points of blow molding process control
1) For extrusion blow molding Attention should be paid to control the sag and wrinkle defects of the parison. If the overhang is too long, the wall thickness will be reduced and the remaining material removed will increase; if the overhang is not enough and the parison is too short, it cannot be inflated.
2) Wrinkle phenomenon
When the parison drops to a certain length, it occurs because the upper melt of the parison cannot bear the weight of the parison and generates circumferential stress; generally, the melt strength is higher, the diameter expansion of the parison is small, the extrusion rate is high, and the die gap is large. Some help to improve wrinkles.
3) Uneven wall thickness
Another problem is that when the parison is lowered, the wall thickness is uneven. Usually, a hexagonal nut is installed on the die of the machine head, which can be used to adjust the gap between the mandrel and the die.
4) Exhaust
To obtain a good surface quality of the parts, you must pay attention to the exhaust. For example, the PE material is sandblasted on the surface of the mold, and the sandblasting particle size is less than 180#, and the blow mold of hard plastic is used for exhaust holes, exhaust needles and exhaust In addition, increasing the inflation pressure is also helpful to improve the appearance of the product.
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