Why Is Everyone Talking About Magnesium Thixomolding?

 Parkway also offers tight tolerance injection molding of plastics (Magnesium Thixomolding)..

The thixotropic molding of magnesium is a hybrid process that combines lightening-fast shots of die casting with the reciprocating screw of plastic injection molding - but so far, plastic molders have embraced it, while die casters are holding off, industry officials say (Magnesium Thixomolding). ``The majority of our current licensees are injection molding companies,'' said Stephen Le, Beau, vice president of sales and marketing at Thixomat Inc.

Winning converts Injection molding of magnesium has won converts thanks to two strong trends in electronics - smaller is better, and the integration of metal with plastic assemblies done by a single company. Magnesium parts, such as a cell phone housing or a body for an ultrathin laptop computer, can be molded thinner than plastic parts.

But the metal/plastics integration trend is driving magnesium around the world - and beyond just electronics, into automotive, recreation, power tools and other markets, experts said. ``It was the one-stop-shopping concept that really got us into this,'' said Ed Estergaard, vice president of manufacturing at Phillips Plastics Corp. Phillips, one of the U.S.

In the 1970s, researchers had developed a way to mix up molten metal to break up the dendrites, or crystalline structures, that form as metal cools. Dow got involved in the late 1970s. Dow technicians figured an injection molding machine was a good way to mix up magnesium and form it into parts.

For several hours, he heard about plastics technologies. Magnesium Thixomolding. But, Decker recalled, he was a metals guy. ``I said, `This doesn't fit me very well. Do you have anything in metals?' '' Decker recalled. Geyzer called in Connie Balacz, supervisor of the magnesium research. ``I immediately bought into it,'' Decker said.

Magnesium Thixomolding

Now chairman of the board, Decker is amazed at Thixomolding today. ``It's larger, bigger commercially than I ever envisaged,'' he said. Of course, back in 1988, nobody could have predicted the portable electronics revolution. ``But the second surprise was, we didn't expect the strong interest from the plastics industry,'' he said.

Traditional die casting uses a large pot of molten metal to feed the machine, which can be hazardous to workers and creates sludge or foundry dross as waste. Thixomolding, by contrast, uses chips of magnesium similar to plastic pellets. All the heating and melting is done in the barrel, totally enclosed and air-tight to keep oxygen away from the magnesium, which can catch on fire in its molten state.

Instead of cooling, the mold is heated to about 400° F to delay the metal's setup time and fill the part. Most parts have to go through a secondary process to remove the runner and burrs, although machinery companies are developing hot-runner systems. To plastics people, even the word ``magnesium'' sounds strange.

Magnesium Thixomolding

So why are plastics companies checking out Thixomolding while die casters are slow to react? For a plastics molder, the investment decision can be justified by winning new business through offering both metal and plastic fabricating. Le, Beau spelled it out: ``The cleanest business model is to take a current injection molding operation and add four or five or six machines on the end of the factory line.

And do it yourself. Then you've got control on design and tolerances and tools and everything, all under one roof.'' In Toronto, several licensees cautioned that it's not as easy as plugging in the press and starting to mold. They recommended hiring at least one qualified metallurgist. And there will be setbacks.