Causes and solutions of common problems in PET preform molds

Update:23-04-2021
Summary:

Phenomenon 1: PET preform is opaque Reason: It may be b […]

Phenomenon 1: PET preform is opaque
Reason: It may be because the raw material is dry and insufficiently plasticized; or mixed with other plastics, the purity is not high; and the temperature of the material is too low, which causes the PET preform to be opaque.
Solution: Check whether the temperature of the drying material is too low or the injection volume does not match. The raw material must be dried at 165 degrees to a moisture content of less than 0.02%; and the drying must be guaranteed for more than four hours during manufacturing; in addition, you can also try Increase the speed of the screw.

Phenomenon 2: The PET preform is cracked at the gate
Reason: This kind of situation is basically caused by the gate undercut and the gate area is too hot. In addition, the hot runner gate is not concentric with the gate can also cause this situation.
Solution: When the gate area is too hot, the heat insulation of the gate should be strengthened; in addition, the correction of the mold and the gate can solve this problem.

Phenomenon 3: The preform is bent after demoulding
Reason: The eccentricity of the gate hole and uneven cooling will cause the preform to bend after demoulding.
Solution: When this happens, you need to take some measures. When the gate hole is eccentric, you can correct the mold; in addition, reduce the holding pressure, increase the injection speed, extend the cooling, clean the water channel, and increase the cooling water pressure. Can solve this bending phenomenon.

Phenomenon 4: The bottle is not fully blown in the vertical direction
Reason: When this kind of situation occurs, it may be dissatisfied that some preforms have too high temperature adjustment, some dissatisfied preforms have cold blocks, insufficient air pressure, poor blow molding mold exhaust, blow molding mold temperature is too high, preforms The wall is too thin and the longitudinal stretch ratio of the bottle is insufficient.
Solution: Adjust the temperature of the PET preform, do not touch the heated preform and check whether the cold hard block has been touched, increase the air storage pressure, increase the exhaust, add cooling water to the blowing mold, modify the mold, Increasing the longitudinal stretch ratio can solve this problem.

Phenomenon 5: Poor vertical bearing capacity of the bottle
Reason: When the wall thickness is uneven, the preform heating temperature is too high, and the bottle shape is not good, the vertical bearing capacity of the bottle will be poor.
Solution: To solve such problems, it is necessary to improve the uniform wall thickness of the bottle, try to low-temperature and high-pressure molding and improve the bottle design.

0