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“When the castings are used as a


structural part, they must carry the load during a crash event,” Conklin said. “High pressure vacuum diecast- ing gives three times the ductility of conventional diecasting, which opens up a new market.” Making the parts in a vacuum gives


producers the ability to heat treat with- out causing blistering or trapped gas. Tese castings achieve an average of 15% elongation versus 3% elongation in conventional diecast aluminum parts. Traditionally, high pressure vacuum


diecasting has been limited to niche vehicles, but its capability to produce parts meeting crush-zone requirements has drawn interest from car manufac- turers, particularly after the MMLV program resulted in a vehicle that reduced weight by nearly 25% while still passing critical frontal safety tests. OEM interest in structural die cast-


ings for high volume vehicle segments has led to increased vacuum diecasting capacity in the marketplace. In August, Magna announced plans to build a new aluminum casting facility in Birming- ham, Ala., at their KAMTEK facility. KAMTEK will produce lightweight


Most of the MMLV aluminum castings are joined to steel materials using self-piercing rivets and a structural adhesive/sealant.


structural parts based on customer demand from North American and foreign domestic OEMs. “We are seeing more and more


requests from customers to use this technology for high volume vehicle platforms,” Skszek said. The die castings included in the


MMLV concept car are left and right front shock towers, left and right hinge pillars, left and right kick down rails and left and right rear mid-rail castings. According to Magna, the shock


tower is the most common high pres- sure vacuum diecast body application. It combines a number of steel parts into a single aluminum component that weights 40% less. Te cast aluminum shock tower reduced the weight from 7.5 lbs. for the baseline to 4.6 lbs. Te kick down rail, which is located


below the hinge pillar, had the highest performance requirement of the castings. As a chassis reinforcement in the front of the vehicle, it had to show that in a crash, it would not exceed the intrusion speci- fication into the passenger compartment foot well area. Te high pressure vacuum diecasting process allows the casting to be heat treated for stiffness, leading to increased torque load capacity and torsional rigidity to the MMLV body structure. FEA analysis showed the cast kick down rail resulted in better intrusion characteristics in the vehicle compared to the baseline design. Te cast aluminum kick down rail


combines five steel stampings lowered the weight from 13 lbs. to 10 lbs. Te hinge pillar casting integrates


five steel stampings and is about 35% lighter than the baseline, reducing weight from 9.8 lbs. to 7.4 lbs. Finally, the mid-rail casting design integrates 12 rear shock tower and rail compo- nents into a single casting for a weight reduction from 12.5 lbs. to 9.2 lbs.


Joining Metals


One of the biggest challenges in designing a multi-material structure


Aluminum castings make up 13% of the MMLV body-in-white design.


30 | MODERN CASTING September 2015


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