Materials perspective of polymers for additive manufacturing with selective laser sintering
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Inspire AG, irpd – Institute for Rapid Product Development, CH-9014 St. Gallen, Switzerland
Konrad Wegener Department of Mechanical and Process Engineering, Swiss Institute of Technology, CH-8093 Zürich, Switzerland (Received 4 April 2014; accepted 6 June 2014)
The fundamental factors of polymer powders, their importance for successful selective laser sintering (SLS) processing, and the outstanding position of polyamide 12 (PA12) powders in this connection are presented. Considering key factors, the combination of intrinsic and extrinsic properties necessary to generate a powder likely for SLS application is emphasized. Only a specific combination of indicated points leads to success. This is one reason for fewer materials commercially available to date for SLS application. PA12 and some dry blends based on PA12 are today the materials that are used to generate almost all commercial SLS parts. The specific performance of particular PA12 for SLS processing is unmatched from other polymers so far. Reasons are the precise molecular control of SLS polymers for thermal behavior (enlargement of sintering window) and the open chain structure. This is for generation of sufficient mechanical properties and to induce interlayer bonding of successively sintered layers to reduce anisotropic parts.
I. INTRODUCTION
Additive manufacturing (AM) is a general expression for several computer-based methods to transform CAD data into physical objects. Joining materials based on a ‘layerwise’ approach is the common denominator for different AM-techniques.1 AM is opposite to subtractive technologies, e.g., traditional machining like drilling, milling, or grinding, where the material is removed from a preform to achieve a desired shape. This is expressed also in the recently published definition of the first basic ASTM standard for the new AM-Technology (ASTM F2792): “Additive manufacturing (AM) – Processes of joining materials to make objects from 3D model data, usually layer upon layer, as opposed to subtractive manufacturing fabrication methodologies.” Selective laser sintering (SLS) of polymer powders is one component of the ‘layer upon layer’ based additive production techniques, occasionally considered as part of the next industrial revolution.2 Space-resolved solidification of polymer powders with high-energy laser opens countless opportunities to produce customized parts with great freedom of complexity.3 However, there are still some drawbacks obstructing a broader acceptance of SLS in many industries. One important issue is the limited number of available polymer powders
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2014.138 J. Mater. Res., Vol. 29, No. 17, Sep 14, 2014
http://journals.cambridge.org
II. POLYMER PROPERTIES FOR SLS PROCESS
To understand the primary factors influencing the material characteristics a careful consideration of the most important parameters on SLS powder is beneficial. Figure 1 outlines five main factors in this association: powder and particle as wel
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