During the cooling process of the plastic injection molded part, the temperature of the injection mold cavity surface is always uniform; ④ The heat conduction degree of the injection mold surface is certain; The material filling process is regarded as an isothermal process, and the material temperature is uniform); ⑤ The influence of the orientation and thermal stress of the plastic on the deformation of the part can be ignored, and the size of the part has no effect on the solidification temperature. The time standard for opening the mold to take out the part is usually based on the fact that the part has been fully cured, has a certain strength and rigidity, and will not deform and crack when the mold is ejected. The calculation formula also differs depending on the definition of the cooling time..In injection production, the cooling time of plastic injection molded parts accounts for about 80% of the entire injection production cycle. When solving the formula, the following assumptions are generally made: ① The plastic is injected into the injection mold, and the heat is transferred to the injection mold to be cooled; The plastic in the molding cavity is in close contact with the mold cavity and does not separate due to cooling shrinkage, and the melt There is no resistance to heat transfer and flow between the mold wall, and the temperature of the melt becomes the same when it comes into contact with the mold wall. Poor cooling often results in product warpage or surface defects, which affects the dimensional stability of the product. The formula to calculate the cooling time 100% correctly in all situations has not yet been published, but only formulas that are calculated on the basis of appropriate plastic boot tray in China assumptions. Even if the same type of plastic is used for molding, its cooling time varies with the wall thickness, the temperature of the molten plastic, the demolding temperature of the molded part and the temperature of the injection mold
