DETROIT – The developer of a unique – but not new – metal injection-molding technique says it hopes the process will increase the automotive industry’s use of magnesium-alloy components.
Called thixomolding, the process is similar to conventional die casting in that the molten material is shot into a mold. But the similarity ends there.
Steve LeBeau of Thixomat Inc. in Ann Arbor, MI, says at the Society of Automotive Engineers World Congress here that thixomolding offers numerous process advantages over die casting, while also producing magnesium-alloy components that display better tensile and yield-strength values over die-cast pieces.
Thixomolding is a “much cleaner (more efficient) system,” says LeBeau.
Corp.’s ’05 Chevrolet Corvette convertible uses several magnesium-alloy interior pieces made by a licensee of the thixomolding process, the most visible piece being the convertible-top release handle. A GM engineer also co-authored the technical paper presented by LeBeau to detail thixomolding’s advantages.
Thixomolding, says LeBeau, was invented at the Massachusetts Institute of Technology in the late 1970s. The process has been adopted widely in the Asia/Pacific region – it was used to make 60 million parts there last year for the telecommunications sector (camcorder faceplates and the like). But it isn’t in wide use in North America, even by the automotive industry, which seems constantly to be on the lookout for methods to incorporate more lightweight magnesium.
Thixomolding takes magnesium-alloy granules and produces a finished, net-shape component in a single step. The metal granules are fed from a hopper into a chute containing a screw that shears the crystalline structure of the metal into new shapes that more easily adapt to heating and injection.
LeBeau says thixomolding produces components with desirable thin-walled structures and intricate details. He says the process also allows manufacturers to freelance with raw-material compositions to “optimize the properties for the (component) application.”
He also says the process eventually will permit the formulation of highly optimized alloys that use a dozen or more constituents instead of the relatively few found in most of today’s automotive alloys.