Eric Boillat

On the effect of scanning strategies in the selective laser melting process

In the selective laser melting process, one has to strike a balance between power and scan speed. When a small scan speed is used, thermal gradients are important and local solidification can lead to cracks. On the other hand, when high speed is used, the power has to be huge and phenomena due to heat transfer, like delamination or balling, arise. In this paper, we study different possible scanning strategies and we indicate those that lead to homogeneous heating of the part until its melting point. The results are compared to numerical simulations.

Study of the inter-particle necks in selective laser sintering

Purpose – Since pulsed lasers are mainly used in selective laser sintering (SLS) – contrarily to selective laser melting (SLM) – only the exterior of the powder particles is molten while their core stays solid. The purpose of this paper is to investigate the binding mechanism between two particles of titanium powder.Design/methodology/approach – A dedicated experimental setup is used to isolate the particles. They are then irradiated by the laser. SEM micrographs are taken at each step and image analysis is performed. The obtained results are compared with the predictions of a thermal model allowing for the incorporation of the latent heat of fusion and for a realistic surrounding. The absorbed laser intensity is modeled by means of the Mie theory.Findings – The growing of the interparticular necks and the volume of liquid formed for different repetition rates are measured and compared with numerical simulations. A good agreement is found. A new method to easily find the absorption coefficient of the lase...