Layer Manufacturing (LM) technologies like Selective Laser Sintering (SLS) were developed in the late 80's as techniques for Rapid Prototyping (RP). Today, SLS-as well as its derived technology Selective Laser Melting (SLM)-is used as well for prototyping, tooling and manufacturing purposes. This widening of applications is caused mainly by the possibility to process a large variety of materials, resulting in a broad range of physical and mechanical properties. This paper presents a survey of the various binding mechanisms in SLS and SLM, which are responsible for the broad range of materials and applications. Basic binding mechanisms involve solid state sintering, chemically induced binding, liquid phase sintering, partial melting and full melting. Many subcategories can be distinguished based on the type of structural or binder powder composition: single component powder grains (single material or alloy), composite powder grains, mixtures of different powder grains, distinct binder material (sacrificial or permanent), etc. The paper will explain how these binding mechanisms apply for sintering various types of materials: plastics, metal, ceramics and composites (e.g. glass reinforced polymers, cermets, hardmetals, etc.). It gives a survey of research done at the University of Leuven, Belgium, as well as at other European and non-European organizations.

Selective laser melting (SLM) is driven by the need to process near full density objects with mechanical properties comparable to those of bulk materials. During the process the powder particles are completely molten by the laser beam. The resulting high density allows avoiding lengthy post-processing as required with selective laser sintering (SLS) of metal powders. Unlike SLS, SLM is more difficult to control. Because of the large energy input of the laser beam and the complete melting of particles problems like balling, residual stresses and deformation occur. This paper will describe SLM applied to a mixture of different types of particles (Fe, Ni, Cu and Fe 3 P) specially developed for SLM. The different appearing phenomenons are discussed and the process optimization is described. The latter includes an appropriate process parameter adjustment and the application of special scanning strategies. Resulting parts are characterized by their microstructure, density and mechanical properties.

Additive manufacturing is a very promising technique for the production of complex multipinhole collimators and may also be used for producing other complex collimators. The cost of this technique is only related to the amount of powder needed and the time it takes to have the collimator built. The timeframe from design to collimator production is significantly reduced.

The paper describes a new powder composition specially developed for selective laser sintering (SLS). The aim is to obtain a ferro powder that can be sintered without need for a (sacrificial) polymer binder and that results in quasi dense parts that do not need any post-processing like furnace sintering, infiltration or HIP. The powder is a mixture of different types of particles (Fe, Cu, Ni and Fe 3 P). The composition and mixture ratio are justified by using phase diagrams. The powder has been tested using an own developed Nd:YAG SLS machine. The influence of process parameters (laser power, scan velocity, scan spacing and scan strategy) and the microstructural characteristics have been investigated. Attention is devoted to the binding mechanism (liquid phase sintering, through melting) and to the quality of resulting parts (density, balling effect, …).

PurposeTo find the suitable parameters for selective laser sintering (SLS) of selected ferro‐based powders. These parameters will help to create products having appreciable strength shown by the highest density and good surface property.Design/methodology/approachDesign of experiment (L9 Taguchi design) has been used to obtain the parameters in the minimum possible number of experiments. For finding the range of various parameters selected such as scan speed, scan spacing and layer thickness, some preliminary experiments have been performed. In order to carry out varied characterization for a given type of experiment, a number of samples have been made.FindingsAn attempt has been made to observe the correlation between applied laser energy and the properties of the laser‐sintered parts. Taguchi design has been useful and has given the optimized parameters. It has also been found that the infiltration increases the strength of the part substantially compared with the property of end‐used sintered product.Research limitations/implicationsThe present set of experiments was limited by the range of supplied laser energy to the powder system, as the laser power could not be increased.Originality/valueThere is a need to search for alternative powders for manufacturing parts through SLS, which can alleviate the need to depend on customized powders, as these customized powders are limited to be used only with prescribed commercial SLS machines for their best performance. This drawback restricts their general use independent of any particular machine and it is, therefore, required to develop know‐how of powders and related process parameters for SLS. The present work is an effort in this direction in which laser sintering of a specially developed iron‐based powder mixture (Fe, Ni, Cu and Fe3P) has been tested on an SLS machine.