Direct metal laser sintering (DMLS), one of the laser powder bed additive manufacturing technologies produces solid metal parts from 3-D CAD data, layer by layer, by melting/sintering and bonding metal powders with a focused laser beam. In this processes isn't complete melting of powder particles in micro melt pools as well as selective laser melting (SLM) and electron beam melting (EBM). Thus some different stress conditions and defects occur depending on the temperature changes during manufacturing. In this study, this problems is investigated aspect cooling rate. Cooling rate affects the solidification process in the melting (sintering) process such as casting, welding, laser assisted processes. Therefore, it also affect part quality and properties. In the scope of study, it is tried to explain how occurring the internal stresses and distortions differ depending on the cooling rates of geometrically different parts in additive manufacturing. The residual stresses and deformations are analyzed by FEA to see relation with geometry (volume, area) to cooling rate for Ti6Al4V materials. Cube shaped samples at 20, 40, 60, 80 and 100 mm edge dimensions have analysed by using FEA. Besides 10mm cube sample is manufactured as solid and verified both as experimental and numerical. Based on the FEA results, cooling rate values are changed from 1.67 to 16.67. In conclusion, the reasons of the problems occurring during laser powder bed fusion are investigated in terms of the cooling rate in relation with the samples geometry.
On The Relation Between Cooling Rate and Parts Geometry in Powder Bed Fusion Additive Manufacturing
