What are the causes and treatment methods of cavities cracking in preform mold injection molding process?

Ensure that the ejection system of the mold is balanced, the number of ejector robs and cross-sectional area should be sufficient, the demolding slope should be appropriate, and the cavity plate surface should be smooth to reduce stress concentration during demolding. At the same time, the structure of the part should not be too thin, and the transition part should adopt arc transition to avoid stress concentration caused by sharp corners and chamfers.

Reduce injection pressure and speed to reduce the generation of internal stress; appropriately increase mold temperature to make the PET preform products easy to demold; control mold opening speed and pressure to prevent demolding cracks caused by rapid strong drawing of parts.

Avoid using materials that are prone to cracking, such as plastics with excessive humidity or high recycled content. At the same time, appropriate molding raw materials should be selected according to the use environment and requirements of the products, and the quality of the materials should be ensured to be pure.

Regularly check the wear and damage of the mold, and repair the wear and defects on the mold in time. Keep the mold clean and lubricated to reduce the friction and adhesion between the mold and the plastic.

such as using release agent appropriately to reduce the adhesion between plastic and mold; consider the design of exhaust and cold material well when designing the mold to ensure that no excessive cold material enters the mold cavity.