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Short communication Characterization of an aluminum fi lled polyamide powder for applications in selective laser sintering Alida Mazzoli Giacomo Moriconi Marco Giuseppe Pauri Department of Materials and Environment Engineering and Physics FIMET Faculty of Engineering Technical University of Marche Via Brecce Bianche 60131 Ancona Italy Received 31 May 2005 accepted 23 November 2005 Available online 18 January 2006 Abstract Solid free form fabrication SFF techniques use layer based manufacturing to create physical objects directly from computer gener ated models Using an additive approach to manufacture shapes SFF systems join liquid powder or sheet materials Selective laser sin tering SLS is a SFF technique by which parts are built layer by layer off ering the key advantage of the direct manufacturing of functional parts In SLS a laser beam is traced over the surface of a tightly compacted powder made of thermoplastic material In this paper is characterized a new aluminum fi lled polyamide powder developed for applications in SLS This material is promising for many applications that require a metallic look of the part good fi nishing properties high stiff ness and higher part quality 2005 Elsevier Ltd All rights reserved 1 Introduction Solid free form fabrication SFF refers to the physical modelling of a design using a special class of machine tech nology SFF systems quickly produce models and proto typepartsfrom3 Dcomputer aideddesign CAD models 3 D digitizing systems acquired data computer ized tomography CT and magnetic resonance imaging MRI scan data The physical object is manufactured layer by layer transforming the three dimensional prob lem in a bidimensional one SFF systems join liquid pow der or sheet materials to manufacture the physical object Layer by layer SFF machines fabricate plastic wood ceramic metal and composite parts using thin horizontal cross sections of the computer designed model In contrast to traditional machining methods i e com puter numerically controlled machines CNC the major ity of SFF systems fabricate parts using an additive procedure ratherthanmaterialremoval subtractive approach Therefore this type of fabrication is uncon strained by the limitations attributed to conventional machining approaches In fact there are no problems of tool clash and any geometrical shape can essentially be reproduced to a high degree of accuracy in the order of the tenth or hundredth of millimetre on the basis of the selected material 1 2 Most of the SFF techniques can pro duce high quality three dimensional parts with varying degrees of complexity size and shape by means of various photochemical laser sintering guided deposition extrusion layering or sculpting processes SFF parts were fi rstly used as visual aids but with the development of new materials it is now possible to make for example investment casting patterns casting cores and moulds functional prototypes and mould inserts for injection The selective laser sintering SLS process is one of the most eff ective and versatile SFF techniques available today 3 Developed by Carl Deckard for his master thesis at the University of Texas SLS was patented in 1989 SLS is a technique by which objects are built layer by layer from CAD data fi les exported in the industry standard exchange fi le format STL Stereolithography format STL is a boundary representation that consists of a simple list of tri angular facets 4 The basic material developed for SLS 0261 3069 see front matter 2005 Elsevier Ltd All rights reserved doi 10 1016 j matdes 2005 11 021 Corresponding author Tel 39 071 2204290 fax 39 071 2204729 E mail address a mazzoli univpm it A Mazzoli Materials and Design 28 2007 993 1000 Materials September 2003 p 363 70 Fig 9 X ray image portion of cranial bone tissue right and AC sintered sample left Fig 8 Compression upper and bending lower test of the sintered DF black and AC grey specimens On the right the two samples DF a and AC b before and after compression and bending A Mazzoli et al Materials and Design 28 2007 993 1000999 2 Mazzoli A Moriconi G Germani M Infl uence of diff erent manufac turing techniques and materials on the accuracy of anatomical SFF models derived from CT data In Proceedings of the BIOMED 3 conference Innsbruck February 2005 p 64 9 3 Pham DT Gault RS A comparison of rapid prototyping technologies Int J Mach Tools Manu 1998 38 1257 87 4 Stereolithography interface specifi cation Company Literature 3D System Inc 1988 5 Kruth JP Wang X Laoui T Froyen L Lasers and materials for selective laser sintering Assembly Autom 2003 23 4 357 71 6 DuraFormTMmater