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Fig. 7. Frost plugs are inserted into the openings, sealing the water jacket.


the cylinder wall, all while main- taining the desired water jacket cross sectional size. Tis additional woodruff


machining introduces incremental cost, but would consume just a small fraction of the original $80 per piece savings, while producing similar geometry. Te machined holes in the sides of the block are then plugged using core plugs (Figure 7). Tese plugs (sometimes referred to as frost plugs) have been used as a low-cost, reliable method of sealing such low pressure passages in engine blocks for more than 50 years. An added benefit of this new


semi-closed deck HPDC forming method is that the dams introduced provide a marked improvement of the flow path for the molten aluminum during the casting phase. CAE simulation indicates this considerably improved flow pattern will improve cast material proper- ties in the entire head deck face, especially the problematic fire ring area; simulation also points toward significant quality improvements in cylinder wall porosity, potentially easing implementation of spray bore technology where it is sought.


The Challenges and Potential Payoff


Other challenges remain in the


diecasting of engine blocks with increased specific power, among them a need for greater strength in the bulkhead/bearing cap area. However, innovation and technol- ogy are attacking this problem, as well, with additive manufacturing methods now greatly increasing the cooling capability in today’s HPDC tooling, in turn delivering improved mechanical properties in these critical cast areas. Today’s engine designer needs


to consider many factors. How- ever, in a world where savings of even a few dollars in piece price represent a notable victory, the possibility of removing $80 from the price of an engine block could provide a strong incentive to explore this new solution.


38 | MODERN CASTING October 2017


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