Computer-aided design of a semi-permanent mold for the casting of an aluminum spool

A semi-permanent mold was designed to improve the quality and increase the production rate of the casting of an aluminum spool used in the textile industry. Presently, the spool is being cast in a sand mold at a rate of 3 castings per hour. The size and shape of the spool requires it be cast with the flanges in the vertical direction and have six risers. This method requires large quantity of green sand for each mold and generates significant amount of scrap metal. The proposed semi-permanent mold was designed in various stages. First, a preliminary mold was designed using the design practices currently followed in the casting industry. Secondly, PATRAN was used to build the geometrical model of the mold and mesh its surfaces. Thirdly, the meshed geometry of the mold was exported into ProCAST for pre-processing, analysis, and post-processing of the results of the simulation. The results from the casting simulation were evaluated and the design was modified as necessary to remove any problems indicated by the simulation. This redesign-simulation process was repeated until the desired objectives were met. The effect of thermal cycling of the mold was also included. From the results of the simulation of the final design the following conclusions were reached. In the startup cycle, porosity formed at the top flange and the top section of the barrel. However, in the production cycle the solidification was unidirectional resulting in a stronger part with higher surface hardness and without any porosity. The results from the cycling simulation indicated that the mold achieved a periodic temperature distribution after the second cycle, and that the first two parts cast from startup will have the porosity problem mentioned above. Several suggestions are made to reduce or eliminate the porosity problem in the first two cast parts. The semi-permanent mold can be used to cast at a rate of 4 parts per hour, requiring fewer and simpler finishing operations, having much better quality, and at reduced cost.