Optimization Of Laser Selective Melting Forming Process For Metal Pendant Round Hole Structure

Selective laser melting(SLM)technology based on powder bed powdering,laser selective melting,and material layer by layer stack forming,can be used for direct rapid prototyping of special materials such as difficult-to-process metal materials and gradient-function composite materials,In the meantime,it has shown a huge manufacturing advantage in machining metal parts with complex geometric features.However,for the overhang features,there are still some problems of poor forming quality such as overhang surface collapse,sticky powder.In order to improve the SLM forming quality of the overhang structure,this paper takes the overhanging circular hole structure as the research object,taking Ti6Al4V as the experimental material.Firstly,the mechanism of the main defects in SLM forming overhang circular hole structure was analyzed.Then,the process experiment is designed to explore the influence of main process parameters on the forming quality of circular hole.Finally,the forming quality of circular hole is optimized through the optimization of solid part parameters and contour scan parameters of circular hole.The main contents of the research is as follows:(1)Based on the current research status and experimental experience of SLM,the forming characteristics of SLM for overhanging structure are analyzed.And the defect generating mechanism prone to occur during SLM processing and the common solutions are summarized.(2)Process experiments were designed to study the influence of the parameters such as the aperture of circular hole,laser power,scanning speed,scanning line angle and contour scanning times on the forming quality of overhanging circular hole,the dimensional accuracy and microscopic topography of different areas overhanging surfaces under different parameters were analyzed.(3)Under the premise of ensuring the mechanical properties of the formed part,fixed laser energy density is 26 J·mm-3,changed the laser power and the scanning speed of the solid part of the circular hole,analyzed the relationship of the solid part process parameters between the forming quality of the circular hole,obtained the optimal combination of the laser power and the scanning speed.(4)By changing the laser power of forming circular hole contour scanning,the influence of contour scanning parameters on the size precision of circular hole and the quality of hanging surface was studied.At the same time,through a single track experiment,analyzed the relationship between the stability of the forming pool and the forming quality of the overhang circular hole.(5)The combined model of horizontal overhang and curved surface overhang is designed.The influence of scanning line angle on overhanging surface under different laser power is verified by experiment.