Awards have been announced in the North American Die Casting Association (NADCA) Die Casting Product Competition for the best examples of aluminum, zinc, and magnesium die cast components. Winners stretch the technological envelope, represent design ingenuity, and reduce part costs.
According to Dr. Stephen Midson, NADCA Director of Research and Technology, winners epitomize what today's product designers can achieve working closely with die casting engineers early in design planning.
The first-place winner for aluminum was a safety-critical replacement of a fabricated and welded steel stamped assembly. Other first place winners were die cast zinc and magnesium replacements for failed plastic injection molded components.
New Safety-Critical Al Application Cuts Weight 50%
The first-place award for aluminum was given to the safety-critical, front suspension cross member on one of Mazda's car models. The part was a 50 inch long squeeze casting produced from A356-T6 Al alloy.
It is the latest example of an automotive cross member being successfully cast in aluminum. According to the die caster, Hiroshima Aluminum Industries of Hiroshima, Japan such parts cast in either low pressure die castings or gravity can't match the properties of the squeeze cast part.
The part replaces a fabricated and welded assembly of many steel stampings. Weight of the new suspension component is 20 pounds less than the steel assembly, a 50 percent reduction. Its greater dimensional accuracy improves precision alignment, and suspension performance. Noise is reduced and shock absorbency, provided by aluminum, is improved. The design flexibility provided by die casting resulted in an optimum configuration with improved space utilization.
Net-Shape, Flash-Free Zn Out-performs Plastic
A zinc die cast housing for a power seat adjusting system designed by Rockwell International replaced a plastic injection molded housing. The housing castings, given the zinc first-place award in the competition, are part of the gear box assembly that drives a car seat fore and aft.
The original plastic housing could not hold the tight tolerances required. The worm gears and bearings could not he held precisely in position, which resulted in an unacceptable operating noise. Also, the flatness tolerance of the housing to the base plate could not contain the grease inside the gear box housing.
Aluminum and magnesium were ruled out because the required tolerances could not be held, and machining was too costly.
The die caster, Fishercast of Peterborough, Ontario used finite element analysis to identify stress points. This enabled Fishercast to strengthen the part in critical areas and remove excess material in noncritical areas for weight and cost reduction. This effort, and the inherent rigidity and strength of the zinc alloy used, Zamak 5, allowed the die castings to meet all loads encountered during critical crash tests.
Specifications called for very close linear, concentricity, and flatness tolerances. Angled core slides were used to cast two holes at a 15 angle, eliminating the need for any secondary machining on the holes. The parts were die cast to net shape, flash free, with no gate removal, trimming, deburring, or machining operations required.
Mg Chosen Over Plastic for 'Ruggedized' lap Top
The Itronix X-C 6000 notebook computer was redesigned as a higher-powered, lap-top 'ruggedized' for use by mobile workers in the field-on a performance-tuned wireless communications hardware platform. Faced with new requirements for RF shielding, better heat transfer for hotter processor chips, and the need for greater impact strength and rigidity, Itronix engineers explored die casting. The resulting magnesium die cast housing assembly, produced by Hartzell Manufacturing of St. Paul, MN won the magnesium first-place award.
The six parts of the die cast assembly -- housing, housing base, keyboard bezel, PC door, and front and rear display frame -- form the main structural chassis to which all primary electronics are attached. The AZ91D magnesium alloy used in the casting provided the higher level of RF shielding required. Also, its excellent heat transfer characteristics eliminated the need for custom heat sinks that plastic would have required.
The magnesium alloy also produced a stronger housing, which allowed a larger display screen with greater rigidity, yet thinner walls. And, it eliminated a wobbling plastic hinge problem.
Engineers initially questioned the corrosion resistance of magnesium, but the selection of AZ91D high-purity alloy eliminated this concern. While estimated magnesium part costs were higher at the outset, cost savings resulted from simplifying the design.
Despite magnesium weighing 1.5 times as much as plastic, the higher stiffness of the magnesium alloy, and the simplified design, yielded a final housing weighing 14 percent less than the plastic version. The judges also commented on the excellent fit and surface finish of the parts.
Second Place Awards
Five die castings won second-place awards in the NADCA competition: a child's bicycle and an automotive crankshaft in aluminum; a window operator gear and a handgun slide in zinc; and an in-line roller skate bracket in magnesium.
Innovative High-Volume Al Bike Frame
A new aluminum die cast frame for a Huffy 20 inch bicycle placed second in the aluminum competition. This was the first time a die cast frame has been used in a high-volume bicycle. It replaces conventional welded steel tubing and was inspired by the cast aluminum seat supports seen during a day at the Cincinnati Reds Riverfront Stadium.
This innovative design makes the strengthening, girder-like ribbing in the die cast frame an integral part of the bike's aesthetic appearance -- with recyclability an added bonus. This frame styling would have been impractical with steel weldment fabrication.
The frame is die cast in Al 383 alloy to net shape, with no machining required, by BTR Precision Die Casting of Russellville, KY. Finite element analysis during the structural design phase ensured that high strength was achieved at minimum frame weight and lowest part cost.
Al Crankshaft Beam Offers 45% Cost Reduction
An aluminum die cast crankshaft bearing beam for Ford Germany's new Zetec engine tied for second place in the contest's aluminum category.
A simultaneous engineering team at Morris Ashby Castings in Witham, county of Essex, England developed the final simplified component as an integrated one-piece die casting. The part connects five crankshaft bearing-caps to dual beam sections at a significant weight saving and a 45 percent reduction in cost over the alternative.
Vacuum die casting resulted in flatness tolerances that eliminated several machining steps, with enhanced stiffness that improved noise, vibration, and harshness performance.
Zinc Die Cast Gear Cuts Costs Over 50%
Hartzell Manufacturing was recognized with a second place prize for zinc as well as with their first place prize. Their second-place prize was awarded for a one-piece, zinc die cast gear for an Anderson window drive system. It replaces three pieces: a two-piece, machined brass helical gear assembly; a steel center bore insert; and a plastic washer.
The new Zamak 3 gear, a simplified design with diagonal teeth cast by Hartzell, utilized the strength and bearing properties of zinc and the production efficiency of die casting to reduce costs over 50 percent compared with the brass-steel-plastic assembly.
Zinc Handgun Slide Keys $750,000 Yearly Savings
A zinc die cast slide for a Smith & Wesson handgun is the company's first departure from conventional gun manufacturing. This critical part, which houses the barrel, extractor, and firing mechanism, tied for second place in the zinc competition.
Cast from Zamak 5 alloy to near-net-shape by Kennedy Die Castings of Worcester, MA, it replaces a slide precision-machined from solid bar stock -- at a savings estimated at $750,000 annually.
A concurrent engineering team from Smith & Wesson and Kennedy was formed early in product planning to ensure that demanding dimensional tolerances could be cast, and that safety and quality specifications would be integrated at every stage of the process. Zinc was the ideal material choice because of its overall physical and mechanical properties, long-term dimensional stability, stability during recoil, and its ability to be cast to the required tolerances.
Produced in a 4-slide die, the casting requires only minimal secondary machining of several holes.
Lighter, Stronger Roller Skate Bracket In Mg
The premium line of in-line roller skates from First Team Sports utilizes a new magnesium die cast brake bracket that houses the brake assembly. The part replaces an injection molded plastic bracket. The die cast part offers greater strength, stiffness and durability, and, surprisingly to some engineers, lighter weight and lower-cost multi-cavity tooling compared to plastic.
Awarded second place for magnesium, the part is produced by Del Mar Die Casting of Gardena, CA. Thin wall die casting technology allowed the weight reduction, while creating a stronger part. An excellent heat dissipater, the new magnesium bracket eliminates the hot-to-the-touch condition that existed during braking using with the plastic bracket.
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