Te Karma was Fisker’s first endeavor in the automo- tive market. It’s a plug-in, hybrid luxury sports sedan that was first unveiled in 2008 at the North American Inter- national Auto Show held in Detroit. Tough the company had plans to have it in produc- tion in late 2009, the car was not delivered to retail custom- ers until late 2011. According to Fisker reports, 2,000 cars were delivered in the U.S. and Europe as of October 2012.
According to the U.S.
Shown is the tooling design outcome of a high pressure die cast tool with four hydraulic slides in a die orientation optimized based on multiple flow simulations.
Environmental Protec- tion Agency (EPA), the Karma’s range, with a full tank of gas and fully charged battery, is 230 miles. EPA rates its com- bined city and highway fuel economy equivalent to 52 miles per gallon. The car also includes a solar panel on its roof to assist in both climate control of the interior and charging its battery.
Why Die Casting A number of factors ultimately
lead to the choice of a die cast- ing. Production volume, however, was key. The diecasting process offers the ability to produce higher quantities of parts per hour, which ultimately is more cost-effective. While Fisker has high production
plans for its Karma, the company’s anticipated 12,000 main transmission 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
transmission housing lay in the machining, cross-drilling and leak- free requirements of the part. “Die casters look at a part like that and see horror in front of them,” Olson said. “Thick walls and a lot of machining and cross- drilling presents difficulties, plus there’s porosity in the high pressure die casting process which we expe- rienced and had to work through.” Mercury utilized flow simulation
software that showed the company where they would need part geom- etry changes for castability and filling purposes along with facilita- tion for gating. Mercury Marine also
26 | MODERN CASTING February 2013
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