different customer who requested these geometrical adjust- ments, i.e. a larger diameter of the cylindrical section and geometrical adjustments in the ram’s head. The aim was to investigate the effects of a cooling plate located underneath the casting. In order to place the plate, the gating system had to be changed from bottom filling to side filling. New vertical runners were added to support filling in higher sec- tions of the casting and the chills were rearranged. In or- der to ensure sufficient cooling of the very bottom, thicker chills were added around the conical bottom section of the casting. New chills were incorporated into the top head section of the casting. The changes are seen in Figures 5 and 11. Besides the mentioned geometrical changes, all casting and simulation parameters are the same as in the first casting arrangement.
Case Study Description 3— Optimization of the Riser and Chills
After inserting all datasets and parameters into the stan- dard simulation environment, the manually refined cast- ing layout in Figure 5 was assessed to create a reference
solution to compare with the optimization results. It had been decided to try to reduce the size of the top riser as much as possible to increase the casting yield, providing that there were no defects occurring in the casting due to the riser’s reduced size. When the riser and the chills were transformed into parametric objects, the optimization pro- cess was initiated. The design variables (those which are subjected to optimization) are dimensions of the chills, height and thickness of the bottom cylindrical chills, and of the top riser, height, bottom and top diameters, and top diameter of the riser neck, see Table 2.
The main optimization objectives are to design the top riser so the casting is sound (i.e. with minimum shrink- age and centerline porosity) and at the same time the top riser’s volume is as small as possible to increase the casting yield. In this context, ‘casting yield’ is defined as the gross weight including the riser and the gating system divided by the weight of the fettled casting. In terms of the MOOP, we deal with minimization of two conflicting objectives (min. porosity in the casting body vs. min. riser volume).
Table 1. Material Settings in MAGMAsoft®
Table 2. Design Variables for Optimization
International Journal of Metalcasting/Fall 10
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