Process Optimization Of Thin Wall And Overhang Structure In Selective Laser Melting

Selective laser melting(SLM)technology is a new rapid prototyping manufacturing technology developed based on the concept of additive manufacturing(AM).The limitations of existing designs in traditional manufacturing technology are overcome,and metal parts of various complex shapes can be directly formed.Thin-walled structures and overhanging structures are the basic elements in complex structures.The forming quality of the two structures directly affects the forming quality of complex structures.Therefore,the research on forming these two structures by SLM technology is very necessary.At present,in the process of forming thin-walled and overhanging structural parts using SLM technology,the parts are prone to warp and deformation due to the structural wall thickness and small inclination angle,which affects the quality of the parts.Therefore,it is necessary to optimize the SLM processing technology for forming thin-walled and overhanging structures.In this paper,the combination of finite element simulation and experiment is used to analyze the SLM forming process of thin-walled structures and overhanging structures,and the above problems are studied and summarized as follows:Firstly,ANSYS finite element simulation software is used to establish the finite element model of thin-walled structure and overhanging structure.The Gaussian heat source model is used to simulate the heat source during the machining process,and the temperature fields of the SLM machining process of the two structures are simulated separately.The information of the molten pool size and temperature distribution of the thin-walled structure under different process parameters is obtained,and the variation of temperature with path and time is discussed.The temperature distribution under different scanning strategies is obtained,and the temperature variation of the marked positions is analyzed.Secondly,combined with the finite element simulation results,the Central Composite Design(CCD)method is adopted to optimize the process parameters of the SLM forming thin-wall structure.The effects of laser power,exposure time and point distance on the forming quality of thin-walled structures are studied.The prediction model of SLM forming thin-walled structure about surface roughness,forming thickness and reliable forming height is established.According to the test results,a regression equation is obtained and its significance is tested.Through parameter optimization analysis,the best experimental conditions that meet the optimization criteria are obtained.The causes of common defects in SLM formed thin-walled structures are analyzed.Finally,based on simulation analysis,three different scanning strategies are used to form the overhang structure.The effects of different scanning times and distances on the surface morphology and roughness of the overhang structure under three scanning strategies are studied.The defects such as warpage,spheroidization and sticky powder during processing are analyzed.The result shows that the quality of the overhang sample can be improved by using the filled contour scanning strategy,and the overall forming quality is significantly better than the other two.It can be formed below the overhang critical angle,and the overall roughness value is small.The research of this subject lays a foundation for the production and application of SLM technology.