Appliance Design - October 2008 - (Page 13)

PROTOTYPING An ABS-like m aterial from 3D Systems. selective laser sintering (SLS), which uses powdered polymers and powdered metals; Objet Geometries’ PolyJet system that uses jetted photopolymers; and Z Corp. 3DP technology, which uses an adhesive to selectively bind polymer powders. Each prototyping method has its own pluses and minuses. Stereolithography has a quality surface, but is typically not good for products that require long-term durability. FDM and laser sintering systems are better for durable, manufactured parts, but part accuracy isn’t as high as an SL system. A Z Corp. 3DP machine is fast, clean, and colorful, but parts can suffer from reduced durability and accuracy. However, the new materials that have hit the market have blurred these general lines, with improvements reducing some of the minuses of some, while playing up the strengths of others. Stereolithography Stereolithography has been one of the more popular of the rapid prototyping methods, as it was first on the scene. With SL, prototypes are built by tracing a laser beam over a vat of liquid photopolymer. As the laser beam touches the material, the polymer immediately begins to solidify. After a layer is traced, it is lowered and covered with more liquid and the laser is traced back over the new layer of material to create the part’s second layer. In this way, successive layers of the photocurable resin are built up into a multidimensional part. The SL method tends to create parts with a good surface finish and fine detail, but they typically require a post-curing operation to complete the chemical process. Without this secondary curing, the chemical reaction that solidifies the material can continue, causing property changes to the material. Parts can warp and become brittle, and the useful lifetime of parts made from these types of resins are limited. A drill housing made with 3D System’s ABSlike Accura 55 material. A power saw prototype made with Dimension 3D Printing’s ABS material. www.applianceDESIGN.com But new materials have been made available that solve some of these issues. DSM Somos, of Elgin, Ill., has developed several new SL materials including the DMXSL 100. Brian Bauman, technical service and product manager, says the material was designed to bridge the gap between prototyping and manufacturing. It delivers the accuracy of stereolithography with sintered-like durability and is targeted to applications that previously would have required SLS or FDM prototyping. It has impact strength of 0.8 J/ cm, and a flexural modulus ranging from 2,000 to 2,400 megapascals (MPa). The DMXSL 100 has the stiffness of standard ABS-type resins, but with more than twice the impact strength, plus up to 20 percent elongation at break, he says. Bauman says that to track durability, impact testing was conducted over a three-month period at temperatures of 30 DegC, 54 DegC, and 85 DegC. Prior to test, impact resistance was 0.8 j/cm, and after 3 months of impact testing, the results ranged from 0.49 j/cm for applianceDESIGN October 2008 13 http://www.applianceDESIGN.com

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Appliance Design - October 2008 Contents Editorial Shipments/Forecasts News Watch Prototyping - Materials Play the Part Prototyping - Mix & Match Motors Electronics Coatings Design Marts Association Report: AHRI Advertiser's Index

Appliance Design - October 2008

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