Process planning for rapid manufacturing of plastic injection mold for short run production

Abstract

<p>This thesis presents a process planning methodology for a rapid injection mold tool manufacturing system that involves additive and subtractive techniques, whereby slabs are sequentially bonded and milled using layered tool paths. Mold tools are grown in a bottom up fashion, eliminating the need for multi-axis machining operations (beyond three axes) and allowing small features in deep cavities. In this research, a new layer bonding method using friction stir welding of aluminum plates is presented. In this manner, one can create seam-free laminated aluminum injection mold tooling using a unique combination of industrial adhesives and friction stir spot welding to initially secure the slab, then continuous friction stir welding of layer perimeters that are sequentially machined in a layer wise process. The original research is presented as a journal article. This research includes three areas of interest that will enable highly automated process planning.</p> <p>The first research area focuses on determining the process plan for applying adhesives on the laminated plates that will be sufficient to resist the forces acting on the plate due to subsequent friction stir spot welding. The use of fixtures and clamps for machining in rapid manufacturing create a potential problem for collision of the tool/spindle and the workpiece setup. Therefore, the process proposed in this thesis uses a combination of industrial adhesives and friction stir spot welding to secure the aluminum plates for machining.</p> <p>The second area focuses on determining the number, location and sequence of friction stir spot welds sufficient to secure the plate prior to continuous friction stir welding. The use of adhesive alone is assumed to be not sufficient to withstand the high forces involved in the friction stir welding process. Therefore, there is need to friction stir spot weld the plates to hold them against the previously formed stack. The location and the number depend on the geometry of that particular layer.</p> <p>The final research area focuses on creating a toolpath planning method for the friction stir welding and CNC machining of each laminated plate. The FSW toolpath is generated based on a predetermined offset distance from the boundary of the polygon representing each cross sectional slice of the mold, while the CNC machining uses a basic waterline toolpath strategy.</p> <p>The impact of this research is that it will provide a completely automated process planning approach for rapid tool manufacturing that is currently not possible using existing additive- or subtractive- only approaches.</p>