Appliance Design - November 2008 - (Page 17)

Metals & Metal Parts THIXOMOLD VS. DIE-CAST PART COMPARISON Net EMI/RFI Material Tolerance Thin Wall Shape Shielding Properties Capabilities Capabilities Excellent Excellent Excellent Excellent Excellent Good Average Average Good Average Excellent Average Fair Average Fair Process Thixomold Die Cast Squeeze Cast Complexity Excellent Average Fair Comparing thixomolding to die cast parts by factors such as complexity and part cost on a 1-5 scale (1=poor, 5=excellent) Source: Advance Forming Technology injection-molding machine, that component could be converted to a molded metal part. Parts made from lighter materials such as magnesium are also being used as a replacement for plastic. One appliance manufacturer has switched from a plastic housing to metal because it is more durable. In this case, the metal’s mechanical properties outweighed the economic justifications for plastic. While plastic costs were lower in this case, the metal parts’ advantages in terms of strength, inherent EMI shielding, thermal resistance and conductivity combined to sway the manufacturer to change the material in its product. Choosing between the three methods can be a simple matter, or one with a great many variables. If a part must be made from stainless steel due to thermal issues or other factors, than metal injection molding is the only option among metal molding processes. The other two molding methods are limited in material selection: the Thixotropic technique only uses magnesium and Cool Polymer’s alloy is a zinc and aluminum blend. However, choices are not always so cut and dry. Cost is obviously a big concern and metal injection molding is generally more expensive than the other technologies. The cost of the metal powders, which can be as much as three times that of magnesium, as well as the metal injection molding process itself, can be cost prohibitive and typically requires higher volumes of parts to cover these extra costs. Material costs are one reason that smaller parts are best suited to the metal injection molding process. As the size of the part rises, so do the extra material costs, as well as the fewer parts per batch that can be processed. At Phillips, the largest metal injection molded part was only 150 grams. Compare this to the magnesium process, which might be as heavy as 10 www.applianceDesIGN.com AD01084AmerN.indd 1 applianceDesIGN November 2008 17 12/10/07 11:26:17 AM http://www.americannickeloid.com http://www.americannickeloid.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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