Causes and treatment methods of common problems in PET preform molds


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, I will explain to you several common problems, causes and treatment methods of PET preform molds .

Phenomenon 1: PET preform is opaque

Reasons: Maybe it is because the material is boring and lack of plasticizing; Maybe it is mixed with other plastics and the purity is not high; Moreover, 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 properly matched. It is necessary to ensure that the material is dried at 165 degrees to less than 0.02% moisture content; and it is necessary to ensure that the material is boring for more than four hours during manufacture; Try increasing the speed of the screw.

Phenomenon 2: PET preforms are cracked at the gate

Reason: The appearance of 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, correcting the mold and the gate can handle this problem.

Phenomenon 3: Zigzag after preform demoulding

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

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

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

Reason: When this kind of situation appears, there may be unsatisfied preforms with too high temperature regulation, unsatisfied parts with preforms having cold blocks, lack of wind pressure and air volume, poor venting of the blow mold, too high mold blow temperature, The wall is too thin and the bottle has a lack of longitudinal stretch ratio.

Treatment method: adjust the temperature of the PET bottle embryo, do not touch the heated embryo body and check whether the cold hard block has been touched, increase the gas pressure of the gas storage, add exhaust, add cooling water to the blow mold, correct the mold, Increasing the longitudinal stretch ratio 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 lead to the bottle's straight bearing capacity.

Treatment method: To deal with such problems, 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 planning.

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