Appliance Design - November 2008 - (Page 16)

Metals & Metal Parts Cool Polymer’s metal alloy can be injection molded in a standard injection-molding machine. these parts were made with the metal injection molding process by Phillips Plastics. standard injection molding machine without any preprocessing steps and does not require special equipment. While metal molding methods are not as widespread as other processes, they are being used to make millions of parts in a variety of industries. Phillips Plastics, the Wisconsin based molding company with both magnesium and metal injection molding capabilities, has produced parts for appliances, consumer electronics, lawn and garden tools, medical devices, power tools, and military products, says Wade Cullen, plant manager for Phillips’ magnesium facility. The company has worked on a leaf blower for Toro, speech-generating devices for DynaVox Technologies, and housings for ruggedized military computers for VT Miltope, a Vision Technology Systems company. Some products used multiple technologies. For the computer, some components that needed to be the most durable were made using the metal injection molding process. Other computer components where weight and durability were paramount were made using the magnesium process. Magnesium’s lightweight and inherent shielding properties were the reasons that DynaVox turned to the material for its speech recognition systems. Another custom molder that uses both technologies is Advanced Forming Technologies of Firestone, Colo. Applications included the housing and components of a reciprocal saw, which is made from magnesium, and internal components of the saw, which were made with metal injection molded parts. Perhaps the biggest applications for the Thixomat process are in personal electronics such as a cell phones and cameras, says Steven LeBeau, president of Thixomat. One of its earliest applications was the Mitsubishi ultrathin Pedion subnotebook. The magnesium-encased computer had a total thickness of 18 mm and weighed less than 3 lbs. The versatility of applications is common to these three different methods. Despite their successes, one might ask why one would switch from the well-established methods for making three-dimensional metal parts. The answer varies by method, volume, part size, accuracy, and other factors. Matthew Bulger, plant manager for Netshape Technologies, Sellersburg, Ind., a company that specializes in metal injection molding, says that metal injection molding costs less than CNC machining, and produces better and more intricate feature detail, and thinner walls, than does die casting. He adds that this process is best for small parts with very complex shapes and thinner walls, which cannot be stamped, screw machined, or made with powdered metallurgy. The magnesium process also compares favorably to die-cast magnesium parts, creating parts that have tighter dimensional tolerances, and better tensile strength, yield strength, elongation at break, and density. The molding methods can create near net or net-shaped parts. But, other technologies can also do that. High-end CNC machines can also create very accurate, very intricate parts. In this case, the main advantage of molding complex parts is in the reduced processing costs; a CNC machine might be required to make many passes to create the part, says David Smith, plant manager for Advanced Forming Technologies, and still need to do some secondary machining operations. The design flexibility afforded by a molding program is also another benefit as compared to other methods. A rule of thumb is that if you can make a plastic part on an TYPICAL MECHANICAL PROPERTIES—THIXOMOLDING VS. DIE-CAST MG. AZ91D Property Ultimate Tensile Strength Yield Strength Elongation % Density Thixomolded 295 MPa [43.0 KSI] 184 MPa [26.0 KSI] 10% 98% Die Cast 230 MPa [33.0 KSI] 150 MPa [22.0 KSI] 3% 88% Parts made with traditional thermoplastic and Cool Polymer’s Xyloy metal alloy. 16 applianceDesIGN November 2008 a comparison of the mechanical properties of parts made through thixomolding as compared to die-cast magnesium AZ91D. Source: Advance Forming Technology www.applianceDesIGN.com http://www.appliancedesign.com

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Appliance Design - November 2008 Contents Editorial Shipments/Forecasts News Watch Metals & Metal Parts Gas Technology Displays Quality & Standards New Products Design Marts Association Report: AHAM Advertiser's Index

Appliance Design - November 2008

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