Casting Study: Trim Frame

The instrument incorporates two frames, one for the front panel and another in the rear. Originally the frames were designed as welded aluminium extrusions. In search of alternative methods, the manufacturer looked to zinc graphite permanent mould casting with its low tooling costs and economical low-volume production. The graphite permanent mould process provides the instrument frame with a 125 RMS finish and a total flatness tolerance of less than 0.015 in. As a one-piece, net shape component, the cutting and welding operations are eliminated, and machining is limited to tapping and threading. Overall, tolerances are tighter and scrap is reduced. Redesigning the frames resulted in a 35 percent cost reduction.