In the production of injection injection molding, plastic injection molding cooling time of the workpiece about 80% of the entire injection cycle. Article often leads to poor cooling surface defects or warpage, dimensional stability, impact article. Reasonable arrangements injection, holding pressure and cooling time, improve product quality and productivity.
　　Article cooling time, usually refers to the injection of the plastic melt from the mold cavity is filled can start and play stop when the form is removed article this time. Can start time standard article form is removed, the article often has sufficiently cured, a certain strength and rigidity of the subject, without modification of cracking at the top of the mold.
　　Even with the same kind of plastic molding, it is also the wall thickness of the cooling time, the melt temperature of the plastic, temperature of the release member and the injection mold temperature varies. 100% correct to be able to calculate the cooling time formula has not yet been published in all situations, but only carried out at the appropriate formula to calculate the hypothetical basis. The formula is also defined by different cooling times vary.
　　At present, typically the following three criteria cooling time as a reference:
　　① temperature of the thickest part of the central layer of plastic injection molding member wall, the cooling time of the thermal deformation temperature of the plastic is required;
　　② the injection molding plastic element cross-section the average temperature, cooling the time the molded predetermined temperature article desired;
　　portion of the central surface temperature of the thickest ③ crystalline plastic wall molding, the required cooling to time below its melting point desired, or predetermined crystallization percentage time.
　　When solving the equation, the following general assumptions made:
　　① plastic injection molding in an injection mold injection and the heat is transferred to the injection mold is cooled;
　　close contact ② plastic molding cavity of the mold cavity, due to cooling shrinkage is not isolated, melt and the mold walls and heat transfer without any resistance to flow, instantaneous melt and die wall whose temperature has become in contact with the same. I.e. when filling the plastic into the mold cavity, the surface temperature of the article which is equal to the temperature of the mold wall;
　　cooling ③ plastic injection molding parts, the temperature of the injection mold cavity surface remains uniform;
　　④ degree of thermal conduction surface must injection mold; (melt filling process as isothermal process, and the material temperature uniformity)
　　Effect of orientation and thermal stress ⑤ plastic deformation of parts can be ignored, the size of the article solidification temperature no impact .