Selective Laser Melting of Biocompatible Metals for Rapid Manufacturing of Medical Parts

In recent years, digitizing and automation have gained an important place in fabrication of medical parts. Rapid Manufacturing could be very suitable for medical applications due to their complex geometry, low volume and strong individualization. The presented study investigates the possibility to produce medical or dental parts by Selective Laser Melting (SLM). The SLMprocess is optimized and fully characterized for two biocompatible metal alloys: TiAl6V4 and CoCrMo. This paper reports on mechanical and chemical properties and discusses geometrical feasibility including accuracy and surface roughness. The potential of SLM as medical manufacturing technique is proved by a developed procedure to fabricate frameworks for complex dental prostheses.Mechanical Engineerin

Direct Selective Laser Sintering of Reaction Bonded Silicon Carbide

Three-dimensional reaction bonded silicon carbide (SiSiC or RBSC) parts have been produced by direct selective laser sintering (SLS). Unlike previously investigated processing routes, which make use of a sacrificial polymer binder to form green parts, the parts in this work are built by scanning subsequent layers composed of a mixture of silicon and silicon carbide powders. A fibre laser is used to selectively melt the silicon under an inert argon atmosphere, resulting in porous preforms of sufficient strength for further handling and processing. After impregnation with a graphite suspension and infiltration with liquid Si at 1450°C, highly dense reaction bonded silicon carbide parts are obtained.Mechanical Engineerin

Laser Penetration in a Powder Bed During Selective Laser Sintering of Metal Powders: Simulations Versus Experiments 453

To gain a better understanding and control of the Selective Laser Sintering (SLS) process, more fundamental and modeling work is needed. A simple analytical ray-tracing model has been developed to simulate the energy absorption and penetration in SLS. The model is applied to FeCu and WC-Co powder mixtures, irradiated by Nd-YAG or CO2 laser. It gives an evaluation of the total energy incoupling and optical penetration of the laser beam in a powder bed and an estimation of the sintering zone dimensions. Another model, which considers heat flow by conduction in the bed, has also been used to estimate the sintering dimensions of one laser track.This research is supported by the national fund IUAP/PAI P4/33.Mechanical Engineerin

Investigation on Occurrence of Elevated Edges in Selective Laser Melting

Selective laser melting (SLM) is a layer-wise material additive process for the direct fabrication of functional metallic parts. During the process, successive layers of metal powder are fully molten and consolidated on top of each other by the energy of a high intensity laser beam. The process is capable of producing almost fully dense three-dimensional parts having mechanical properties comparable to those of bulk materials. However, one of the problems encountered in SLM process is the occurrence of elevated ridges of the solidified material at the edges of the successive layers. Those ridges reduce the dimensional accuracy and topology of the top surface. The edge-effect problem is encountered not only in SLM, but also in other production techniques applying melting processes such as LENS® (The Laser Engineered Net Shaping) and EBM (Electron Beam Melting). In this study, the reasons for elevated edges and solutions to this problem are investigated and reported. Different scan strategies as well as different hatching and contour parameters are tested to reduce the edge-effect problem. Besides, the influence of applying laser re-melting in combination to selective laser melting has been investigated. It turns out that re-melting layers deposited by SLM improves the part density and surface roughness, but creates on its own elevated edges.Mechanical Engineerin

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

Survey of Materials and Material Issues in Rapid Manufacturing by SLS/SLM

The paper gives a survey of actual materials that can be processed by Selective Laser Sintering and Selective Laser Melting for rapid manufacturing purposes. It mainly focusses on polymers, but also surveys the various metals that can be processed. It describes the various binding mechanisms that can be invoked and the resulting material properties and structures that can be obtained. For polymers, distinction is made between semi-crystalline polymers, amorphous polymers, de-bindable polymers, reinforced polymers, elastomeric polymers, polymer blends and thermosetting polymers. For metals, it looks at single component metals, alloys and metal composites.status: publishe

CT Metrology for Engineering and Manufacture

X-ray Computed Tomography is a common technology in medical imaging and material analysis. Since a couple of years, new more powerful and more accurate CT devices have been developed suited for dimensional metrology applications in engineering and manufacturing. The paper will shortly introduce the principles of CT metrology and give examples of applications in engineering design and manufacturing. It will demonstrate how CT measurements can be used simultaneously for dimensional and material quality control of manufactured products. This technology opens a new area in production metrology as it is the only measuring technique allowing to measure the internal as well as the external geometry of a product without having to cut and destroy the component.status: publishe

New applications of physical and chemical processes for material accretion manufacturing

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Selective laser melting of biocompatible metals for rapid manufacturing of medical parts

Purpose This paper seeks to investigate the possibility of producing medical or dental parts by selective laser melting (SLM). Rapid Manufacturing could be very suitable for these applications due to their complex geometry, low volume and strong individualization. Design/methodology/approach The SLM-process has been optimized and fully characterized for two biocompatible metal alloys: Ti-6Al-4V and Co-Cr-Mo. Mechanical and chemical properties were tested and geometrical feasibility, including process accuracy and surface roughness, was discussed by benchmark studies. By developing a procedure to fabricate frameworks for complex dental prostheses, the potential of SLM as a medical manufacturing technique has been proved. Findings Optimized SLM parameters lead to part densities up to 99.98 percent for titanium. Strength and stiffness, corrosion behavior, and process accuracy fulfil requirements for medical or dental parts. Surface roughness analyses show some limitations of the SLM process. Dental frameworks can be produced efficiently and with high precision. Originality/value This study presents the state-of-the-art in SLM of biocompatible metals by thoroughly testing material and part properties. It shows opportunities for using SLM for medical or dental applications. © 2007, Emerald Group Publishing Limitedstatus: publishe