BING MOLD LIMITED

Injection molding is a cyclical process wherein melted polymer is forced into a cold metal mold under high pressure and cooled until it is solid enough to be ejected from the mold. Cooling is a crucial part of the injection molding cycle because it has a major impact on both the quality of the part and the productivity of the mold.

Many defects such as residual stresses, shrinkage and warping are caused by non-uniform cooling. These defects affect the quality of the final part in appearance and precision. Cooling can last more than two-thirds of the whole injection cycle, and the design of an efficient cooling channel can reduce the cooling time and improve the productivity of injection. Therefore the design of an optimized cooling system would achieve minimum cooling  time and balanced (uniform) cooling. In order to have a better understanding of the injection molding cooling process, computer aided cooling analysis has been used as a helpful tool for the design of cooling systems and the evaluation of cooling conditions.

Here is a brief description of the development of the simulation of plastic injection molding cooling. The pioneering work of Dusinberre focused on the prediction of temperature and pressure fields on rather simple geometries, and the one-dimensional transient model Finite Difference Method (FDM) was used to calculate the temperature distribution. Later, Keing, Kamai and Singh applied  the two-dimensional Finite Element Method (FEM) to simulate the cooling process. Barone, Cauik, Burton and Rezayat first applied the Boundary Element Method (BEM) to calculate the temperature field, but it was limited to two-dimensional analysis. Since most injection molded parts are of three-dimensional complex geometrical configuration, in order to calculate temperature distributions based on three-dimensional cooling analysis, some researchers used middle-plane BEM to simulate the cooling of injection molding .

Cooling analysis software was developed using the BEM approach and the theory of heat transfer. From this cooling analysis program, temperature distribution can be computed for parts and molds during injection molding. The program can also calculate the temperature profile of the part after being ejected from the mold. Experiments were carried out to verify the accuracy of the program.

The cooling analysis of injection molding is adopted to predict the temperature distribution in both mold and part, using heat transfer theory and BEM to simulate the cooling of mold and part during injection molding, as well as the continued cooling of the part after being ejected from the mold. Experimental results obtained with an injection molded plate of ABS can validate the numerical predictions of the cooling analysis software. Although the numerical simulation results are acceptable, there is still much room for improvement. In order to get more accurate predictions, realistic thermal boundary conditions during cooling, crystalline material and material properties dependent on temperature and time should be taken into consideration when a theoretical mathematical model is being built.