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Combining die-casting and assembly technologies simplifies production, improves quality, and cuts costs.
Swaging, press fitting, crimping, and adhesive bonding are all well-known joining techniques. Zinc-alloy die casting has also earned a place on this list. Zinc alloys can join most materials including metals, plastics, ceramics, glass, paper, fibers, and elastomers. Zinc die casting can help reduce costs by eliminating individual components from subassemblies and is well suited for both joining parts and forming components in a single-step process called Injected Metal Assembly (IMA).
IMA simplifies component assembly by letting designers join components inside an assembly fixture tool that also serves as the casting die or mold. Components are aligned in the fixture then molten zinc alloy is injected into die cavities where it solidifies and shrinks, locking around the parts forming a strong, permanent joint. IMA produces a finished, ready-to-use assembly straight from the mold. Delicate comportents or those susceptible to distortion are good candidates for IMA, as no force is applied during the assembly process.
Components joined by traditional processes can likely be assembled more efficiently with die-casting technology. For example, in an automotive transmission shift assembly a fabricated eyelet crimped to a steel shaft is a simple mechanical operation. However, by die casting the eyelet shape in zinc alloy directly onto the shaft in one step, assembly becomes part of the manufacturing process.
Likewise, a two-piece cam and steel shaft asse bly can be redesigned so that instead of press fitting the prefabricated cam to the steel shaft, the zinc alloy is cast in the shape of the cam directly onto the steel shaft. The alloy's predicable shrinkage mechanically locks the die-cast cam onto the steel shaft. Another example is a recent redesign of a window regulator. Here a stamped steel cup, swaged to a spindle, is eliminated by die casting the cup onto the spindle. In both cases, the cast cam and cup do double duty - serving as an assembly component as well as a joint.
KEEPING TOLERANCES TIGHT
With IMA, part-to-part consistency of the die-cast joint over long production runs is also good and tolerances can be maintained to ±0.002 in. For example, maintaining concentricity on cups and shafts, such as those in cooling fans, can...