Analysis and calculation of cooling time of injection molding workpiece

 

In injection production, the cooling time of plastic injection processing workpiece accounts for about 80% of the whole injection production cycle. Poor cooling often leads to warping deformation or surface defects, affecting the dimensional stability of products. Reasonable arrangement of injection, pressure holding and cooling time can improve product quality and productivity.

The cooling time of the product usually refers to the time between the time the plastic melt fills the cavity of the injection mold and the time when the product can be opened and removed. Can open the mold to take out the time standard, often to the parts have been fully cured, with a certain strength and rigidity, in the opening of the mold ejection without deformation and cracking.

Even when the same plastic is used, the cooling time varies with the thickness of the wall, the temperature of the molten plastic, the demoulding temperature of the molding part, and the temperature of the injection mold. The formula to calculate the cooling time with 100% accuracy in all situations has not yet been published, but only the formula to calculate it on the basis of appropriate assumptions. The calculation formula also varies depending on the definition of cooling time.

At present, the following three standards are usually used as the reference basis for cooling time:

(1) The temperature of the central layer of the thickest part of the wall of the plastic injection molding workpiece and the time required for cooling to the thermal deformation temperature of the plastic;

(2) The average temperature in the section of the plastic injection molding workpiece, cooling to the specified product mold temperature time;

(3) The temperature of the center layer of the thickest part of the wall of the crystalline plastic molding parts, the time required to cool down to its melting point, or the time required to reach the specified crystallization percentage.

Summary：

In injection production, the cooling time of plastic injection processing workpiece accounts for about 80% of the whole injection production cycle. Poor cooling often leads to warping deformation or surface defects, affecting the dimensional stability of products. Reasonable arrangement of injection, pressure holding and cooling time can improve product quality and productivity.

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Date：

2022-11-30

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