Studies On Overhanging Structure And Porous Structure During Selective Laser Melting

Selective laser melting(SLM)is a new laser rapid manufacture technology to directly fabricate any complex shape metal functional parts.The high energy laser beam acts on small area of powder bed which results in excessive or insufficient local energy input.In this study,a three-dimensional temperature field finite element model of 316 L processed by SLM was developed.The effects of energy control on the molding of overhanging structures and porous structures were studied systematically.The input and output of energy per unit volume were controlled by adjusting process parameters.A discussion of overhanging structure fabrication and the design and technical process of controllable porous structure were performed.This paper gives a deep and detailed study on the fabrication of overhanging structure and controllable porous structure using 316 L stainless steel during selective laser melting.The main research contents as follows:1.A three-dimensional temperature field finite element model of 316 L processed by SLM was developed.The thermophysical parameters of 316 L stainless steel at different states were distinguished.Phase change and the absorption and release of latent heat were considered.Point and single scan simulations were finished with the model.The effects of laser power,exposure time and point distance on melting pool dimensions were studied.To conclude,the temperature field model close to actual situation and have a certain reference value for determining the optimized process parameters.2.Research on the SLM fabrication process of overhanging structure was studied.The hanging dross and burnt metal defects occur frequently during overhanging structure fabrication,which deteriorate the quality of part.In order to improve the fabrication quality of overhanging structure,the effect of tilting angle on quality was studied.The hanging dross and burnt metal defects were eliminated by controlling the input and output of energy.Dense overhanging structure was obtained by remelting the part.3.Research on the SLM fabrication process of controllable porous structure was studied.A controllable porous structure was designed based on SLM.The formability of controllable porous structure was studied.Controllable porous structure was fabricated by using optimized scanning strategy and processing parameters.A design method of porous structure with complex surface was proposed and a corresponding part was designed and fabricated.4.Support with controllable porous structure was designed.Modeling method of complex overhanging surface was processed.Overhanging structure and surface with largetilting angle were fabricated by using controllable porous structure.