The Study of Surface Properties in Injection Moldings (Part-1)

—Effect of Molten Polymer Flow in an Injection Molding Die with Multi-cavities—

Abstract

Injection molding is used in various fields. Surface properties are an important subject and there are many reports on them. From the viewpoints of cost and productivity, the injection molding of multi-cavity injection die is used widely. However, there is no report on the research of surface properties in these injection moldings.
In this study, we observed surface state and measured surface roughness for the injection molding with emboss form on the surface and compared with surface state about molding conditions. Moreover, we carried out the optimization of runner design in consideration of simultaneous filling using injection molding flow analysis and considered the influence of runner balance on the surface state. High mold temperature improves surface properties for the whole injection molding. Short filling time improves surface properties for the portions do not require much packing pressure. The optimized runner balance can realize uniform surface properties in multi cavity injection die.