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.
``The majority of our current licensees are injection molding companies,'' said Stephen LeBeau, vice president of sales and marketing at Thixomat Inc.
The company in Ann Arbor, Mich., is the leading proponent of injection molding magnesium alloys - the company's patented technology is called Thixomolding.
Although Dow Chemical Co. and the Massachusetts Institute of Technology developed thixotropic molding in the 1970s, commercialization did not happen until the 1990s. Japan Steel Works Ltd. became the first licensee in 1995, seven years after Thixomat was founded. Husky Injection Molding Systems Inc. followed in 1999. Today, they are the only two Thixomat machinery licensees.
Interest continues to grow. Some 170 people attended the International Thixomolding Magnesium Conference, held May 23-24 in Toronto, right after the World Magnesium Conference in Montreal. The meetings, like the magnesium molding industry itself, drew a diverse range of metallurgists, plastics processors and end users.
In addition to the machinery licensees, there currently are 40 magnesium molders running about 240 machines in eight countries. Six of the processor licensees are North American: five of them in the United States and one in Canada.
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. The parts are very rigid and light. LeBeau called magnesium ``the lightest structural metal in the world.''
Another big selling point: Unlike plastics, magnesium dissipates heat quickly, a growing issue as electronic products shrink.
Because of the explosion in ever-smaller, lighter consumer electronics, most Thixomat licensees are in the Asian electronics hot-bed countries of Japan, Taiwan and China. Japan has 130 presses running, more than half the worldwide total.
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. pioneers, got into magnesium molding in 1999, as the only molder to buy one of Husky's prototype machines. The Hudson, Wis.-based custom injection molder also bought three JSWs.
Phillips' core technology is plastics molding, but the company also was doing metal powder injection molding and ceramic molding.
According to Estergaard, a demanding job led Phillips into magnesium. The project involved a housing and other components for a hand-held bar-code reader. It's the kind of product used by delivery drivers, so it's subject to abuse. The customer said it had to survive a 7-foot test drop onto a cement floor. Light and tough, magnesium proved to be the answer.
Phillips has pushed Thixomolding far beyond portable electronics. At the Toronto conference, the company showed a magnesium snowboard binding and a fishing reel. One envelope-pushing part on display was a one-piece front module for Buell Motorcycles of East Troy, Wis. The part holds headlamps, the instrument panel, electrical components and fairing.
A new Thixomat licensee, BMI-Parkway LLC, was born last year in Erlanger, Ky., driven by electronics' demand for materials integration.
``We see it as a great solution to a certain market niche,'' President Alan Ridilla said during the Thixomolding Magnesium Conference. That niche comprises parts demanding shielding, high strength and good transfer of heat.
BMI-Parkway is a joint venture between Parkway Products Inc., a plastics and rubber processor and metal stamper based in Florence, Ky., and BMI of Palatine, Ill., which makes electronic shielding products.
How Thixomat began
Thixomat almost did not happen. Founder Raymond Decker was a former vice president of technology at a large nickel producer who then became head of research at Michigan Technological University. A University of Michigan graduate with an advanced degree in metallurgy, he moved back to Ann Arbor, Mich., and set up a venture capital company to look for business opportunities.
MIT had developed a way to apply a shearing force to magnesium. 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.
Chips of magnesium are fed into an injection press and warmed by heater bands into a thixotropic, or semisolid, state. Unlike in plastic molding, the screw does not melt the raw material, it just conveys it forward and breaks up the jagged dendrites into round shapes that can be pushed into the mold easily.
``Dow actually developed the technology,'' LeBeau said. ``They spent about $8 [million] to $10 million over about 10 years working on it.''
In 1988, Dow decided to sell off a range of noncore technology.
Decker traveled to Dow in Midland, Mich., and met with Arnold Geyzer, who was in charge of the spinoffs. For several hours, he heard about plastics technologies. 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.
Thixomat was born when Decker was joined by initial investors Dave Dawson and Bob Carnhan.
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.
Decker thought die casters would flock to Thixomolding. 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. Employees use special protective suits when working around the molding area or changing screws.
But it's not exactly like injection molding of plastics, either. One easy-to-see difference is the requirement that molds have to be sprayed with a release agent in between each shot, so the solid magnesium does not fuse itself to the mold. Thixomolding also runs at much higher temperatures - up to 1,200° F - and injection speeds can reach 3,000 millimeters per second. Speakers at the conference described injection as a ``rocket blast'' that slams the metal into the mold. 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. It is mined as ore - increasingly from China - and can be made from salt water.
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.
LeBeau 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. You make magnesium parts on the end of the line and bring those parts right to the assembly area and add mag[nesium] and plastic into assembly. 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.
``It's a classic early-stage technology that you've got to work your way through,'' said Ridilla of BMI-Parkway.
Automotive offers the promise of huge volumes and larger parts.
``Everybody in the magnesium industry is speaking about the automotive industry and all the good the automotive industry can do for magnesium,'' said Claude Winandy, who edits the weekly online newsletter Light Metals News from Denmark.
But there are several roadblocks. Magnesium is a new material for carmakers, and at about 7 pounds per car, is miles behind traditional materials.
``Aluminum and steel, they have muscle,'' Winandy said. As for magnesium, ``This is a small industry. The car industry is a large industry and they are used to working with other large industries, like aluminum and steel.''
In the Detroit area, car engineers drive to work past billboards proclaiming the benefits of steel, aluminum and plastics. The magnesium industry can't afford that. ``We're 1,700 times smaller than steel,'' said Gerald Zebrowski, president of the International Magnesium Association in McLean, Va.
Instead, Thixomat and the IMA work on design manuals and a materials database. They hold workshops.
Despite the underdog role, magnesium has a history in cars. The Volkswagen Beetle in the 1970s used a whopping 44 pounds of magnesium, mainly for its air-cooled engines. (VW switched to aluminum when it went to water-cooled engines.) More recently, the Dodge Viper uses 42 pounds of magnesium for parts like the instrument-panel support beams, and the dash panel.
Winandy thinks sales of magnesium will grow more than 50 percent in automotive by 2010, spurred by the drive to reduce weight in cars.
``Large, thin-walled, multifunction components: That's where you can find your opportunities in the auto industry,'' he said. Potential applications include valve covers, steering wheels, transmission and gearbox housings, and interior door panels.
Chinese producers are driving the price of magnesium down from its current level of about $1.40 a pound, according to speakers. ``This makes it more competitive with steel and aluminum,'' Winandy said. But he said magnesium producers may have to sign long-term contracts to give automakers the pricing stability they crave.