Computer-Aided Design and Fabrication of Molds and Computer Control of Injection Molding

摘要

Results are presented of research undertaken to further develop the scientific base for the injection molding of polymeric materials. The development of an interactive version of the finite-element/finite-difference simulation of cavity filling is reported and experiments on the rheological characteristics of glass-fiber-filled polymer melts are outlined. Efforts to develop a method for obtaining parameter estimates for a controlled system dynamic model in which injection velocity is the controlled variable are discussed. Injection-molding experiments reveal good agreement with inelastic predictions for cavity pressure during filling and have enabled juncture gate losses to be deduced. It is noted that the gate loss decreases with increasing temperature and is significantly smaller for polycarbonate than for polystyrene or polypropylene. Similar results are presented for the juncture loss at the axisymmetric abrupt contraction between circular tubes, as fed by an extruder. The juncture loss for polystyrene and polypropylene is shown to increase with glass-fiber-filler content. Density variation is said to be on the order of a tenth of a percent.