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Analysis of common problems encountered in preform molds
Edit:Taizhou Huangyan Yige Machinery Co., Ltd.   UpDate:2019-09-11

PET bottles are processed again by blow molding to form plastic bottles, including bottles for cosmetics, medicine, health care, beverages, mineral water, reagents and other packaging. This bottle making method is called a two-step method, which is to form a preform by injection molding.

Today, Xiaobian will explain to you several common problems, causes and processing methods of PET preform molds .

Phenomenon 1: PET preform is opaque

Reason: It may be due to the lack of drying and plasticization of the material; or the mixing of other plastics, the purity is not high; and the temperature of the material is too low, which makes the PET bottle embryo opaque.

Treatment method: check whether the temperature of the dry material is too low or the injection volume is not well matched. It is necessary to ensure that the material is dried at 165 degrees to less than 0.02% of moisture content; and it is necessary to ensure that it is dried for more than four hours during manufacture; Try to increase the speed of the screw.

Phenomenon 2: PET preforms are cracked at the gate

Reason: This kind of situation is basically caused by the undercut of the gate and the gate area is too hot. In addition, the misalignment of the hot runner gate and the gate can also cause this situation.

Treatment method: When the gate area is too hot, the insulation of the gate should be strengthened; in addition, the correction of the mold and the gate can handle this problem.

Phenomenon 3: Zigzag after preform release

Reason: The pain of the gate hole and uneven cooling will cause the preform to twist after demoulding.

Treatment method: When this situation occurs, some measures need to be taken. When the gate hole is painful, the mold can be corrected. In addition, reduce the holding pressure, increase the injection speed, extend the cooling, arrange the water channel, and increase the cooling water pressure. Can handle this twisty phenomenon.

Phenomenon 4: The bottle is not blown in the straight direction

Reason: When such a situation occurs, it may be that the temperature of the dissatisfied preform is too high, the block of the dissatisfied preform has a cold block, the air pressure and air volume are insufficient, the exhaust of the blow mold is not good, the temperature of the blow mold is too high, The wall is too thin and the bottle lacks the longitudinal stretch ratio.

Treatment method: adjust the temperature of the PET bottle embryo, do not touch the heated embryo body and check whether the cool hard block has been touched, increase the air pressure of the gas storage, increase the exhaust, add cooling water to the blow mold, correct the mold, Large longitudinal stretch ratios can handle this problem.

Phenomenon 5: The bottle's straight bearing capacity is poor

Reason: When the wall thickness is uneven, the preform heating temperature is too high, and the bottle shape is bad, it will cause the bottle to have a poor straight bearing capacity.

Treatment method: To deal with this kind of problem, it is necessary to improve the uniform wall thickness of the bottle, as far as possible low temperature and high pressure molding, and improve the bottle shape design.


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