A television powerhouse tunes in to TXMA television powerhouse tunes in to TXM

By: Carl Kirkland

Yukio Nishikawa is the senior staff engineer in the materials and processing R&D group of the corporate production engineering division at Matsushita Electric Industrial Co. Ltd. of Osaka, Japan, better known in the U.S. as National/Panasonic. Though he admits that much work lies ahead in improving the productivity of the process, he is confident that magnesium TXM has a bright future in the markets Matsushita serves.

In fact, he and his colleagues have produced a 36-inch magnesium TV cabinet on a Model JLM1600-IU850, a 1600-metric-ton JSW TXM machine, the world's largest, which is in their lab.

Unlike a similarly sized plastic TV frame, the magnesium cabinet is strong enough to support the weight of the entire TV—90 kg—all on its own. What's more, it is inherently EMI shielded, thermally conductive, and doesn't need to be painted. Nishikawa also reports that Matsushita has built a new captive and custom TXM plant near Tokyo.

Environmental concerns in the Japanese electronic home appliance market are one of the major reasons why Nishikawa says Matsushita is tuning in to TXM. Stringent new laws proposed in April 2000 are now in full effect in Japan. They stress the source reduction, reuse, and recycling of home appliances such as TVs, washing machines, air conditioners, and refrigerators. Consumers now bear the recycling costs for these items.

Nishikawa says the recycling ratio of plastics is only about 20 percent today. What is not recycled is burned in Japan, which reportedly releases environmentally harmful dioxins.

"From a hardware supplier's perspective, newer products must be smaller, thinner, and lighter; they must be mobile and safe; and they must be more ecologically friendly," he says.

Greener Than Plastics

Matsushita's production engineering lab has been actively investigating magnesium as an alternative to plastics since 1996. It has researched the diecasting of magnesium, as well as TXM. Nishikawa says Matsushita has found that TXM has a number of important advantages over diecasting.

He says TXM is safer and cleaner because it's a more closed process. There's no generation of ozone-depleting gases that some say are produced during die-casting. And he says the semisolid nature of the melt in the TXM process produces higher-quality finished products.

TXM products are lightweight and rigid. The superior heat conductivity of magnesium enables Matsushita to eliminate the radiation apertures on its products, a plus in big TVs. Magnesium, which is available in abundance, is inherently EMI shielded—EMI radiation is considered to be a serious health risk in Japan. And, as far as the environment goes, Nishikawa says Mg products have an 80-plus percent recycling ratio.

TXM products have a high-quality appearance and feel. The cost of the parts is going to be equivalent to plastic parts, according to Nishikawa, and large quantities can be delivered quickly and easily—100,000 pieces/month. Also, Mg parts will have a comfortably short development cycle. Adding up all these pluses, Nishikawa expects that the market for magnesium TXM parts could grow by more than 200 percent per year. Still, he says there is much development work that needs to be done, particularly in manufacturing.

Manufacturing R&D

"TXM has a small material cost ratio," he says. "There needs to be fewer postmolding processes involved to reduce WIP and inventory. Cycle times have to be reduced, as do the amount of labor involved and the capital equipment costs."

Nishikawa and his associates have discovered that control over solidification time, injection time, and flow have the most significant impact on part quality. Mold temperature, injection velocity, and mold design have been found to be extremely influential factors in controlling the molding process. Control over all of these variables is key to improving TXM productivity at Matsushita.

Nishikawa also has found it best to use water as a modeling material when running flow analyses since he says magnesium, like water, splashes into a mold cavity.

He has found there to be no differences whatsoever when running either new or recycled magnesium chips in regard to the molding process, part mechanical properties, or part corrosion resistance. AZ91D magnesium alloy is most used at Matsushita. However, there are economical concerns in other areas when it comes to taking advantage of magnesium's recyclability, especially the costs involved in recovery of painted parts.