Casting Study: Capstan Retainer

Precision and strength are important design considerations for the minicartridge tape drive, and the capstan retainer is a good example. This part is actually two separate components cast together–a Torx head screw with an integral retainer sleeve. To produce the capstan retainer, a two-step “intercasting” process is utilized, which reduced costs by combining four parts of a prototype (screw, washer, arm, and sleeve) into a single component ready for assembly. In this process, the screw is cast in the first of two cavities. The threaded subcomponent is then indexed over to the second cavity, and the wing is cast around it. Because the inner threaded portion can rotate within the outer part, the intercasting process effectively acts as both a casting and automated assembly process.