Process chain analysis of the dimensional integrity in a metal-insert polymer smart phone baseplate - from die casting to polymer injection molding

摘要

Given the rapid development of die casting and polymer injection molding technologies, injection molding with metal-insert products, such as smart phone baseplate, can be widely produced and used. Injection molding usually has a complicated shape and high precision. Residual stress and related warping, local bending, and shrinkage are the key problems that affect the final product quality. These defects are generated because of temperature change, pressure, and cooling regime. In this research, finite element method was carried out to process chain analysis from die casting to polymer injection molding. This method predicted the residual stresses during the packing and cooling stages of die casting and polymer injection molding. The reason of distortion after ejection as well as the magnitude and distribution of distortion were also analyzed. To verify the calculated distortion after ejection, we compared the numerical analysis results with the experimental results that were measured by 3D scanning technology. The calculated deformation was consistent, and the residual stress was formed because of the different thicknesses of the sheets that resulted in different cooling rates, causing thermal stresses to become unevenly distributed. After the ejection, the uneven residual stress caused local distortion.