Barrier Screw Design for High-Performance Plasticizing in Injection Molding

Short cycle times in the injection molding process due to fast and effective cooling of the molds extend the demands for novel screw concepts starting from double-flighted screws and leading to barrier screws with dispersive and distributive mixing elements. We present different high-performance screw concepts for various applications in the injection molding industry. Besides a comparative view of different screw designs, we focus on modelling the plasticizing process in barrier screws using our recently developed software S3 (Screw Simulation Software) to investigate both the melting and the melt conveying process in more detail. The three-dimensional helix shape of the screw channel consisting of feed, barrier and metering section can be approximated via an unwound screw channel. Melting performance, pressure build-up and temperature distribution can be calculated numerically based on physical models and finite-difference approximation schemes. The axial screw motion during the plasticizing process and the idle time during the injection and holding phase are considered as well. Our simulations show good agreement with experimental studies conducted with various screw sizes and barrier configurations.