Injection Molding of Semicrystalline Thermoplastics Exemplified by Acetal Resins.

A knowledge of the processes taking place during the filling of the mold in injection molding is of decisive importance for the production of industrial plastics moldings with close tolerances. It is particularly important to take account of the dependence of attainable production tolerances on the shape of the article and the different flow and cooling conditions within it. Here, the expected shrinkage and post-shrinkage of the molding must be taken into account when designing the mold, so as to ensure optimum molding quality. These relationships are much easier to understand today, thanks to recent measurements. The article seeks to analyse the connection between formation of the molding and shrinkage behavior and to discuss ways and means of improving production control during the injection molding of partially crystalline thermoplastics.