Extrusion blow molding machine parison

I Why is the extruded parison prone to bending? How to solve it?

(1) The main reason for the bending of the parison

In the extrusion blow molding process, the main reasons for the bending of the parison are as follows.

①The flow channel in the die is not smooth or the center of the die is not centered. The die gap is large on one side and small on the other side, and the parison will bend to the side of the die gap.

②The uneven heating of the die head causes the temperature of the melt to be uneven, which causes the inconsistent pulling action of the extruded parison due to its own weight.

③Extrusion rate is too fast, causing the melt to accumulate in the die, causing the parison to bend.

(2) Solution

①Check the flow channel of the machine head and adjust the center of the machine head to make the gap of the die uniform

②Adjust the heating temperature distribution of the machine head to make all parts heated evenly.

③Reduce the extrusion rate.

II Why does the extrusion blow molding parison appear curling? How to solve it?

The reason for the curling phenomenon of the extrusion blow molding parison is mainly caused by the unreasonable temperature control of the die, which causes the temperature difference between the inner and outer surfaces of the parison. When the extruded parison is curled to the inside, it may be that the die temperature is too high. If the blank is curled to the outside, the core temperature may be too high. The solution is mainly to control the temperature of the die and core mold of the machine head to be consistent, and to keep the temperature of each part uniform. When the extruded parison appears to be curled to the inside, the temperature of the die should be lowered at this time. If the parison is curled to the outside, the core temperature should be appropriately lowered.