E-shots Web Exclusive: Low Porosity is a plus
November 1, 2003
"Things are going pretty well now," says T.K. Lee, senior sales engineer for Yamazen Inc. (Cypress, CA). "Several customers around the world are looking into what we have to offer. Of the major Mg molders here in the U.S., two are very interested in our Mg-Plus molding system."
Sodick supplies the solid rod-shaped Mg alloy used in its Mg-Plus series of two-stage hybrid molding systems. The barstock is pushed through a zoned heating cylinder that softens the rod in the middle zone and melts it at its far end.
The melting cylinder is sealed off from any possible oxidation problems by the molten portion of the Mg rod. Melt is fed into a second cylinder, where a plunger injects it into the mold. (See "A Mg Molding Dream Come True," November 2002 IMM, pp. 64-65 for an initial report.)
Sodick’s Mg billets were recently tested for porosity by one of the largest North American TXM molders, who wishes to remain anonymous. Its barstock was found to exhibit very low porosity.
"Sodick’s test part and billet are excellent due to the lowest porosity level, refined microstructure, and constitutional homogeneity," researchers at the TXM molder concluded.
MELT VS. SLURRY
In tests conducted at various lengths along the flow path of test parts, very few pores were observed, except in overflows. Chemical analysis and tests on filling speed, packing pressures, and nozzle cavity thermal control are pending.
So far, Sodick has sold four machines, ranging from 80 to 180 metric tons. All were sold in Japan. Mg-Plus presses are available in four models from 80 to 260 metric tons.
"We have found that our process can produce very thin-wall parts at very good yield," says Lee. "I think that has a lot to do with the fact that we’re shooting molten Mg, rather than Mg slush, like the thixotropic molding process.
"The melt temperature of AZ91-D Mg is 650C. The thixotropic process calls for melt temperatures of only 630C. Our machine goes up to 700C."
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