Meeting the Magnesium Challenge
Lightweight alloys make automotive LED lamp assemblies lighter and more cost effective. DENISE KAPEL, SENIOR EDITOR
A
s fuel costs rise and efficiency standards tighten, lightweight
alloys such as magnesium present new opportunities for metalcasters serving the automotive and trans- portation industries. Te Obama administration recently finalized standards requiring increased fuel economy equivalent to 54.5 mpg for cars and light-duty trucks by model year 2025. Te program includes incentives for automakers employing advanced technologies to improve vehicle characteristics such as weight. Michael Pickholz, CEO of tech-
nology development company Mag- Werks LED, Oxford, Mich., recently went looking for a metalcaster that could prototype lightweight, reli- able LED (light-emitting diode) lamps for automotive customer Sealink International, Largo, Fla. Jack Ziemba, owner and CEO of
30 | MODERN CASTING November 2012
Aristo-Cast Inc., an Almont, Mich., investment casting facility, had just the solution for him. Ziemba had developed a propri-
etary process for magnesium invest- ment casting in-house, which over- came the metal mold reaction that occurs with magnesium and the silica shell material and reliably achieved cast wall sections as thin as 0.02 inch (0.5 mm). Initially, Pickholz worked with Aristo-Cast on a 7-inch (17.8- cm) round, AZ91E magnesium alloy LED headlamp he had invented. Fol- lowing the success of that project, the companies collaborated on a proto- type for a fog lamp.
The Process “We tell [our customers], ‘Put
everything you want into your cast- ing, and we’ll tell you what we can and can’t do,’” said Paul Leonard, vice president, Aristo-Cast. “In this case, there were some very minor modifi- cations that had to be made, such as
some radii added.” “If we’re allowed to deviate from the design by adding a radius, it improves the whole operation and adds to the strength of the part,” Ziemba said. “On the exterior, if you have a sharp edge, it becomes a weak spot when you’re building the shell.” Oxygen in the shell also presented
a challenge. “Magnesium in a molten state is hungry for oxygen,” Ziemba said. “It will grab hold wherever it can, and that’s one of the things you want to keep from happening. Te fused silica shell is SiO2
come up with a method that would isolate the magnesium and stop it from grabbing the oxygen out of the shell, which would be detrimental to the surface finish.” Aristo-Cast exposes the shell
material to a proprietary treatment at the end of the process. “Every- thing up to that point is conven- tional gravity-pour investment
so we had to
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