Proceedings of the 4th Bi-Annual PMI Conference vol:4 pages:296-302
Polymers and Mould Innovations Conference edition:4 location:Ghent date:15-17 September
Water-assisted injection molding (WAIM) is one of the latest techniques to produce hollow or partly hollow plastic parts. With advantages like a faster cycle time, flexibility in design, less warpage and shrinkage and a better surface finish, WAIM overcomes its better known competitor gas assisted injection molding (GAIM). However, the molding window and the process control become more difficult so that the tooling and the mold process design will be more complicated. In that way the experience of the conventional molding process is no longer sufficient. This study investigates the influence of the melt and process parameters on the product quality of water-assisted injection molded tubes, using a design of experiments. This DOE is carried out with two different melts (PP and HDPE) and five process parameters (water hold time, water injection delay time, flow rate, mold and melt temperature) that vary at three levels. The residual wall thickness and the part weight will serve as response functions to determine the part quality combined with a visual inspection of the part surface. It was observed that the water injection delay time and the flow rate had the major influence on both the RWT and the part weight. Furthermore, parts produced with the PP showed a lower RWT and part weight in comparison with the HDPE.