Taguchi optimization of the surface finish obtained by laser ablation on selective laser molten steel parts

Laser ablation consists in laser-material interaction which causes the vaporization of material from the work-piece being machined. It is proper for difficult-to-machine materials, like carbides, ceramics and hardened steels and it is very flexible at micro-fabrication of moulds and other micro-system devices. The material is ablated by a laser beam through a layer-by-layer mechanism. Some recent studies investigated into the possibility to use this process to improve surface quality of selective laser molten steel parts. The selective laser melting (SLM) process is a layered additive manufacturing technique for the direct fabrication of functional parts by fusing together metal powder particles. The focus of this study was to perform a Taguchi statistical analysis of laser ablation main process parameters in order to s elect those which reduce the surface roughness of selective laser molten parts. Taguchi proposed a quadratic loss function as the objective function for optimizing a product or process design. The laser speed, power, focus and the number of removed layer were studied through a reduced experimental plan. Some significant evidences were found on the sensitiveness of the process to those parameters so optimal strings of laser parameters were selected versus the number of removed layer.