Optimization of Scan Strategies in Selective Laser Melting of Aluminum Parts With Downfacing Areas

Selective laser melting (SLM) is an additive manufacturing technique in which metal products are manufactured in a layer-by-layer manner. One of the main advantages of SLM is the large geometrical design freedom. Because of the layered build, parts with inner cavities can be produced. However, complex structures, such as downfacing areas, influence the process behavior significantly. The downfacing areas can be either horizontal or inclined structures. The first part of this work describes the process parameter optimization for noncomplex, upfacing structures to obtain relative densities above 99%. In the second part of this research, parameters are optimized for downfacing areas, both horizontal and inclined. The experimental results are compared to simulations of a thermal model, which calculates the melt pool dimensions based on the material properties (such as thermal conductivity) and process parameters (such as laser power and scan speed). The simulations show a great similarity between the thermal model and the actual process

Melt Pool System Identification and Feedback Control for Selective Laser Melting

Observation of the melt pool, formed during a normal Selective Laser Melting (SLM) build process, shows a non-uniform melt pool intensity distribution throughout one layer and scan track. The associated variation of the melt pool intensity can cause unwanted defects (e.g. pores). The change in melt pool intensity and possible defects cannot only be observed within one layer but will propagate itself throughout all the layers. To counteract the change in melt pool characteristics, a system identification was performed on the melt pool intensity, during several layers, in function of the laser power. The system identification provides a mathematical model of the melt pool intensity that was used for the development of a feedback controller. The benefit of the feedback controller was simulated.status: publishe

Production of AlSi10Mg parts with downfacing areas by Selective Laser Melting

status: accepte

Dimensional accuracy of internal channels in SLM produced parts

status: accepte

Optimisation of Scan Strategies in Selective Laser Melting of Aluminium Parts With Downfacing Areas

Selective Laser Melting (SLM) is an additive manufacturing technique in which metal products are manufactured in a layer-by-layer manner. One of the main advantages of SLM in the large geometrical design freedom. Because of the layered build, parts with inner cavities can be produced. However, complex structures, such as downfacing areas, influence the process behavior significantly. The downfacing areas can be either horizontal or inclined structures. The first part of this work describes the process parameter optimization for noncomplex, upfacing structures to obtain relative densities above 99%. In the second part of this research, parameters are optimized for downfacing areas, both horizontal and inclined. The experimental results are compared to simulations of a thermal model, which calculates the melt pool dimensions based on the material properties (such as thermal conductivity) and process parameters (such as laser power and scan speed). The simulations show a great similarity between the thermal model and the actual process.status: publishe

Processing AlSi10Mg by Selective Laser Melting: Parameter optimization and material characterization

AlSi10Mg is a typical casting alloy which is, due to its high strength/density ratio and thermal properties, highly demanded in aerospace and automotive industries [1]. The alloy combination of aluminium, silicon and magnesium results in a significant increase in strength and hardness which might even reach 300 MPa and 100 HBS, respectively, by applying a proper heat treatment [2]. Selective Laser Melting (SLM) of AlSi10Mg, may be interesting to open new application areas such as heat sinks with complicated geometry [3], and therefore is taken under investigation in this study. The process optimization of SLM for this alloy is not straightforward due to high reflectivity and conductivity of the material. In this study, the main goal is to optimize the process parameters, namely scan speed, scan spacing and laser power, to achieve almost full density and good surface quality taking productivity as a key issue. A relative density up to 99% is achieved with an average roughness (Ra) of about 20 µm measured on horizontal top surfaces while the scanning productivity is about 4.4 mm3 /s. The reasons spherical and irregular porosity formed are investigated. Moreover, microstructural analysis of the SLM samples is conducted.peerreview_statement: The publishing and review policy for this title is described in its Aims & Scope. aims_and_scope_url: http://www.tandfonline.com/action/journalInformation?show=aimsScope&journalCode=ymst20status: publishe

Mechanical properties of AlSi10Mg produced by Selective Laser Melting

Selective Laser Melting (SLM) is an Additive Manufacturing (AM) technique in which a part is built up in a layer- by-layer manner by melting the top surface layer of a powder bed with a high intensity laser according to sliced 3D CAD data. In this work, mechanical properties like tensile strength, elongation, Young's modulus, impact toughness and hardness are investigated for SLM-produced AlSi10Mg parts, and compared to conventionally cast AlSi10Mg parts. It is shown that AlSi10Mg parts with mechanical properties comparable or even exceeding to those of conventionally cast AlSi10Mg can be produced by SLM.status: publishe

A holistic approach for μEDM milling on SLMed steel

Maraging steel mould insert blanks have been produced selective laser melting (SLM) and then they are further processed by micro electrical discharge machining μEDM) to generate the desired features. In order to reach high efficiency manufacturing of micro features, a holistic approach with this micro-sparking technique is pursued at University of Leuven. Accordingly various upgrading has been carried out on a commercial SARIX® machine, including monitoring and controlling of the stability of the sparking process (gap variation and energy distribution etc.), wear compensation of the tool-electrode, and on-machine metrology. Preliminary experiments have been carried out with promising results in terms of production time and shape accuracy.status: publishe

Fine-structured aluminium products with controllable texture by Selective Laser Melting of pre-alloyed AlSi10Mg powder

This study shows that AlSi10Mg parts with an extremely fine microstructure and a controllable texture can be obtained through Selective Laser Melting (SLM). Selective Laser Melting creates complex functional products by selectively melting powder particles of a powder bed layer after layer using a high energy laser beam. The high energy density applied to the material and the additive character of the process results in a unique material structure. To investigate this material structure, cube-shaped SLM parts were made using different scanning strategies and investigated by microscopy, X-ray diffraction and electron backscattered diffraction. The experimental results show that the high thermal gradients occurring during SLM lead to a very fine microstructure with submicron sized cells. Consequently, the AlSi10Mg SLM products have a high hardness of 127 ± 3 Hv0.5 even without the application of a precipitation hardening treatment. Furthermore, due to the unique solidification conditions and the additive character of the process, a morphological and crystallographic texture is present in the SLM parts. Thanks to the knowledge gathered in this article on how this texture is formed and how it depends on the process parameters, this texture can be controlled. A strong fibrous texture can be altered into a weak cube texture along the building and scanning directions when a rotation of 90° of the scanning vectors within or between the layers is applied.status: publishe