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Lightweight alloys make automotive LED lamp assemblies lighter and more cost effective.


s fuel costs rise and effi ciency standards tighten, lightweight alloys such as magnesium present new opportunities for casting designers and buyers serv- ing the automotive and transportation industries. In August, the Obama administration fi nalized standards requiring increased fuel economy to the equivalent of 54.5 mpg for cars and light-duty trucks by model year 2025. T e program includes incentives for automakers employing advanced technologies to improve vehicle characteristics including weight. Michael Pickholz, CEO of technology devel-

opment company MagWerks LED, Oxford, Mich., recently went looking for a metalcaster that could prototype lightweight, reliable LED (light-emitting diode) lamps for automotive customer Sealink International, Largo, Fla. Jack Ziemba, owner and CEO of Aristo-Cast Inc., an Almont, Mich., investment casting facil- ity, had just the solution for him. Ziemba had developed a proprietary process for magnesium investment casting

in-house, which overcame 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. Following the success of that project, the companies collaborated on a prototype for a fog lamp.

The Process “We tell [our customers], ‘Put everything you want into your casting, and we’ll tell you

what we can and can’t do,’” said Aristo-Cast Vice President Paul Leonard. “In this case, there were some very minor modifi cations that had to be made, such as some radii added.” Ziemba noted that fi llets, the rounding-out of internal corners of the pattern, and

radii, added to round-out the external edges, are extremely important in investment casting. Adding a radius enhances the metalcaster’s ability to build the optimal shell. “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 exteri-


or, if you have a sharp edge, it becomes a weak spot when you’re building the shell.” Another noteworthy character- istic of magnesium is its low density. “You don’t get much of an advantage from the head pressure [exerted by the column of molten magnesium].” Oxygen in the shell also presented

a method that would isolate the mag- nesium and stop it from grabbing the oxygen out of the shell, which would be detrimental to the surface fi nish.” Aristo-Cast exposes the shell mate-

rial to a proprietary treatment at the end of the process. “Everything up to that point is conventional gravity-pour investment casting shell build,” Ziemba explained. Aristo-Cast’s process also prevents the magnesium from igniting due to the presence of oxygen.

Magnesium’s Advantage While traditional incandescent au-

tomotive lamps are housed in injection- molded plastic, high-powered LED lamps require a metal heat sink, as they

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. T e fused silica shell is SiO2

so we had to come up with

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