INJECTION MOLD PROCESS OPTIMIZATION FOR SURFACE MICROFEATURE CONTROL

摘要

A method for creating regular arrays of surface features in the 10um to 200um range over large areas in metallic materials enables the use of treated surfaces on injection molds. This surface control is used for manufacturing products with controllable optical, tribological, heat transfer, and surface tension properties. However, the flow, filling, and solidification behavior of molten polymer at the micro scale is not well understood. Therefore, the purpose of this study is to derive a range of robust solutions for injection molding of these micro-featured surfaces. The approach includes numerical simulation of flow under different molding conditions, which drives input variable and range selection of a large design of experiments study. This study uses critical inputs of the molding process, mold geometry, and working materials, and determines a range of feasible solutions to recreate these micro structures without filling or demolding defects. Five different molding parameters hypothesized as most influential in molding microstructures were varied and the resultant micro-features characterized using 3D surface profiling white light interferometry and scanning electron microscopy. Regression responses were determined and optimal value ranges for the key input parameters were identified and independent tests run to verify the results. The five parameters tested are: injection pressure, injection velocity, mold temperature, melt temperature and shape of micro structures. These tests were carried out in both HDPE and EPDM/PP alloy [1] materials using different mold insert materials and coatings.