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Less residual stresses in laser beam melting through a holistic approach including laser, scanning, material and machine parameters

Paper presented at Fraunhofer Direct Digital Manufacturing, March 12-13, 2014 Berlin; DDMC 2014
Reduzierung von Eigenspannungen im Laserstrahlschmelzen mittels eines ganzheitlichen Ansatzes einschließlich Laser-, Scan-, Material- und Maschinen-Parameter
 
: Müller, Bernhard; Töppel, Thomas; Kranz, Burkhard; Hoeren, Karlheinz P.J.; Grimm, Tobias; Witt, Gerd

2014, 8 pp.
Direct Digital Manufacturing Conference (DDMC) <2014, Berlin>
English
Presentation
Fraunhofer IWU ()
additive manufacturing; laser beam melting; selective laser melting; residual stress; distortion; simulation; FEA; scanning strategy; powder preheating; support structures

Abstract
With Additive Manufacturing by Laser Beam Melting (LBM), components are built up layer by layer directly on the basis of 3D CAD models. Using a focused laser beam, metal powder gets selectively melted and solidifies to a solid body. Depending on the material-specific thermal conductivity, the cooling rates reach speeds up to 3.5 x 106 K/s, leading to extremely high temperature gradients, resulting in thermally induced residual stresses. These high residual stresses often lead to undesirable part distortions or even component and process failures. As part of an ongoing research project, different laser, scanning, material and machine parameters are being investigated for an improved process reliability through reduction of internal stresses in Laser Beam Melting. Analysed parameters are scanning strategies, support structures, pre-heating of the powder via a novel radiation heating system and powder layer properties. The experimental studies are supported by LBM process simulations. The holistic approach to address all major parameters that have an influence on the residual stress behaviour of Laser Beam Melted parts is supposed to establish a significant optimisation step, lowering residual stresses in LBM parts substantially. Preliminary results of the research work are presented in this paper.

: http://publica.fraunhofer.de/documents/N-287085.html