“Typically, the product designer
is focused on issues such as the part functionality, operating environments, failure modes, secondary operations and cosmetics,” said Mark Ratcliffe, manufacturing engineer. “Te engi- neers who will design the casting and its tooling, on the other hand, will be concerned with material flow, gating and coring issues, part shape vari- ability, hot and cold spots, shrinkage, parting lines, solidification patterns and porosity.” Recently, Christie experienced
some problems with a cast magne- sium light engine enclosure in one of its digital projectors that had been produced in Asia. Due to significant challenges, Christie began to reex- amine the casting’s sourcing strategy. “Tere were a few simple goals with the project: to identify and reduce design constraints as well as cost drivers where practical, while
ensuring such changes would not impact any mating parts,” said Adele Evans, director of global supply chain management. Te design for the problematic
casting was sent to one of Christie’s existing casting suppliers for quo- tation purposes. During a phone call after receipt of the drawings, engineers discussed some technical issues for the enclosure, which had been a two-piece casting produced via thixomolding, a process of injec- tion molding of a semi-solid alloy. In exploring possible solutions, the two sides pursued a concept of the hous- ing that would turn the component into a single magnesium die casting. Within a few months, collab-
orative technical discussions and flow analyses were taking place for the one-piece design. Reducing the component to a single cast- ing would reduce part count ratio,
ONLINE RESOURCE
Take a look at more castings used in projector applications in the online gallery at
www.moderncasting.com
improve physical and mechani- cal properties, simplify inventory management and minimize required machining. “With the original design, not
only did you have a two-piece assembly, which is more expensive, but you also had the assembly com- ponent to it,” said Eric Voss, Chris- tie advanced product developer. Te two-piece assembly also could “result in potential final assembly issues on the production line.” By simplifying the assembly into a single diecast component, Christie and its supplier decreased shipping, tooling and machining costs while improving the casting design. Te
Sand cast aluminum or steel, the flat baseplate that forms the floor of the projector’s interior cavity supports the entire unit. February 2015 MODERN CASTING | 29
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