Effect and control of hatch length on material properties in the direct metal laser sintering process

As one of the advanced rapid prototyping and manufacturing processes, the direct metal laser sintering (DMLS) process gives designers the possibility of building parts of almost any complexity in a wide range of metal materials. In DMLS, the sintered material is anisotropic and heterogeneous, affecting the quality and performance of the built parts. This paper presents a study that focuses on these two material characteristics and proposes a method to control them. Firstly, a series of experiments have been designed and conducted to study the influence of material anisotropy and heterogeneity on the built part strength. The heterogeneity was analysed and the microstructural changes due to different hatch line lengths were observed using scanning electron microscopy. The relationship between the hatch line length and the part quality is derived on the basis of experimental data collected and an appropriate statistical analysis applied. A genetic algorithm method is also proposed to optimize the hatch direction for obtaining more homogeneous sintered material properties. The experimental results verify that the negative effect of varying hatch lines in the early sintering process can be controlled effectively.