Casting Study: Drive Beck

The drive deck for Cherokee’s 5-1/4 in. WORM optical drive utilises a ZA-12 graphite permanent mould casting. From the start, graphite permanent mould was the process of choice because of its economical tooling cost, good dimensional control and low-volume economies. In this case annual requirements run between 2,000 and 3,000 units. ZA-12 and graphite permanent mould casting satisfy two important manufacturing process requirements— stiffness and minimal machining. Previous experience with aluminium investment casting did not produce the required stiffness. ZA-12’s high zinc content provides the deck with excellent sound and vibration dampening characteristics. The deck is cast square along all planes. The whole process is controlled to the point where the decks are ready for finish matching right out of the mould, eliminating preparatory machining. Three as-cast pads on the deck’s underside serve as machining locator points.