Simple Solutions That Work! Issue 16

32 and searching for a maximum or minimum value for the selected objective function. The most common method for optimizing a casting for soundness would be to specify one or more porosity predictors as constraints, and then maximize the process yield. This allows the system to identify those designs which produce a sound casting, then select the design which maximizes the material yield. OPTIMIZATION CASE STUDY Here is a quick example to show how optimization has been applied in the foundry. Figure 1. Optimization Process Flow The casting was being made successfully. That is, a sound part was being produced. The goal was to maximize casting yield by reducing the riser size, while still maintaining part soundness. Figure 2 shows the shrinkage prediction for the part with the original riser. The variables selected for optimization were the height and diameter of the riser. Since there were 8 castings per mold with one riser each, the risers were linked together for optimization. Figure 3 shows two of the risers selected. The height and diameter were scaled, so that the riser and contact would expand and/ or shrink during the optimization runs. A single constraint was selected; macro-porosity. The casting needed to be shrinkage-free to be considered good. Loss of density in any part of the casting would be cause for rejection. The objective function of the optimization was to maximize casting yield. Since the casting shape would not change, this means that the riser size would need to be reduced to maximize the yield. Once the optimization run starts, the entire process is automatic. In this example, 26 simulations