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housings to be produced annually is not typically a high enough production for many diecasters to consider the job. “Mercury is more of a low volume shop than many die casters, due to the volumes we cast for ourselves for our marine product lines,” Olson said. “Te lower volumes are more of our niche, and we don’t shy away from the most difficult of parts as is evident with our marine product as well.”


Complexities and Design Plans


Te difficulty in casting Fisker’s A close-up of the transmission housing shows the many complexities in the diecast part.


process, customers should weigh their tooling payback based on anticipated volume to determine the worth of the diecasting process. High production parts will even out the high cost of tooling, saving money in the long run. When launching a new product, a company may start a component as


a sand casting, if initial production is on the low side. When production ramps up, it generally becomes more cost-effective to switch to the diecasting process. While Fisker has high production


plans for its Karma, the company’s anticipated 12,000 main transmission


transmission housing lay in the ma- chining, cross-drilling and leak-free requirements of the part. “Some die casters look at a part like that and see horror in front of them,” Olson said. “Tick walls and a lot of machining and cross-drilling presents difficulties, plus there’s po- rosity in the high pressure die casting process which we experienced and had to work through.” Mercury utilized flow simulation


software that showed the company where they would need part geometry changes for castability and filling pur- poses along with facilitation for gating. Mercury Marine also needed to in- corporate gate sawing into its tooling plans due to its gating design. Datum schemes, or machining locators, were designed and put into place, as well. Te company cast the hous- ing using its own, proprietary alloy (XK360 or 362.0), a high-strength ductile aluminum alloy close to A360. Tis particular alloy was chosen for its increased corrosion resistance and mechanical properties. After six months, Mercury Marine


was producing HPDC transmission housings for Fisker’s Karma. Te fin- ished die casting weighs in at just under 55 lbs., measuring 15 x 13 x 14.25 in. “We expedited the tooling de- sign and procurement process to less than six months as timing was of the utmost importance. Tis was achieved by using our internal tooling division, Capitol Engineering out of Brookfield, Wis.,” Olson said. “I would say, if you are going to start from scratch with a fresh design, you should plan on nine months, at least.” 


36 | METAL CASTING DESIGN & PURCHASING | Nov/Dec 2012


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