Classification and Simulation based Design of 3D Junctions in Castings

Many casting defects, which cannot be eliminated by changes to tooling and process parameters, can be attributed to poor design of the part with respect to manufacturability. One such common defect is shrinkage porosity occurring at casting junctions. We present a generic classification of 3D casting junctions in terms of the number, thickness and cross-section of converging elements (walls), and the angle between pairs of elements. These junctions have been modeled, and simulated for solidification to predict the extent of shrinkage porosity defect using Vector Element Method. The results are shown for 'L' junctions with varying fillet radius (both inner and outer) and validated by experiments, followed by parametric analysis to formulate design for manufacture guidelines. Finally, a benchmark part with 3D junctions is presented to show how simulation can be used to predict and prevent the defect by modifying the junction design.