| Selective Laser Melting(SLM)is one of the most promising technologies in the field of additive manufacturing.The technology uses the layer-by-layer superposition principle of metal powders to achieve the manufacture of parts,with a wide range of materials and design flexibility.It has a wide range of application prospect in the field of manufacturing of high-precision,high-density,high-mechanical metal complex thin-walled structural parts.As the basis and carrier of SLM technology,the selective laser melting equipment has a great influence on the forming process of the SLM and the performance of the formed parts.Existing SLM molding equipments are limited by factors such as forming size,processing efficiency,forming accuracy,etc.,thus can't meet the needs of large-size,high-efficiency,and high-precision forming equipment in the fields of aerospace,biomedical,automotive,and mold.This paper aims to develop a large-size selective laser melting equipment,and analyzes the error and correction method of SLM forming equipment.The research content mainly includes the optical system design of multi-beam movable galvanometer platform,the optical distortion of galvanometer scanning,the geometric error analysis of forming equipment,and the integrated error correction.The main research contents and conclusions are as follows:(1)According to the performance parameters such as the processing size,forming accuracy and processing efficiency of the SLM forming equipment,the overall design of multi-beam galvanometric scanning optical system is performed,and the selection,assembly and commissioning of the main optical components are completed according to the overall design scheme.(2)The optical distortion error in galvanometric scanning system was studied.Two mathematical models were set up for the two different scanning modes of pre-objective and post-objective scanning system.Matlab simulation analysis of the relationship between the error of the pillow distortion,focus error and compound distortion and the characteristic parameters of optical system.For composite distortion,the study found that the distortion increases with the increase of the deflection angle of the galvanometer,when the deflection angle of galvanometer?_x(28)?_y(28)10~?,the degree of distortion in x direction?_x(28)1.65%,the degree of distortion in y direction?_y(28)1.86%;when the deflection angle of galvanometer?_x(28)?_y(28)20~?,_x?(28)1.862%,?_y(28)7.98%.(3)For the geometric error of SLM forming equipment,a geometric error model based on multi-body system was established.Combined with the projection model of scanning galvanometer,a comprehensive error model was obtained.The study found that the positioning error of specified axis in the linear displacement error of the galvanometer platform and the lifting platform is only related to the error of the integrated component in the axial component,and the effect of the magnitude of the positioning error on the axial component error of the integrated error is a linear accumulation effect;The research on the influence of angle error on the integrated error has found that the angle error of galvanometer platform has far more influence on the integrated error than lifting platform,and the angular error of galvanometer platform(35)?(y)-(35)?(y)plays a decisive role in y direction error of the integrated error,(35)?(y)-(35)?(y)plays a decisive role in x direction error.(4)For the comprehensive error of SLM forming equipment,a comprehensive correction model combine error compensation surface accurately mapped based on actual coordinate points and galvanic mirror deflection angles and grid look-up table correction was established.Compare the error values before and after correction,the error value is greatly reduced in the entire area after correction.In the entire scanning area,the maximum error in x direction is reduced from-1.6829mm before correction to-0.1163mm,and the maximum error in y direction is reduced by-1.9253mm before correction to 0.0973 mm. |
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