Research On Process Strategy Planning Method Of Laser Powder Bed Fusion Based On Multi-feature Recognitio

Laser Powder bed Fusion(LPBF),as one of the representative technologies in the field of metal additive manufacturing,provides a strong support for the direct manufacturing of complex metal parts in aviation,aerospace,medical and other fields.Reasonable and effective planning of laser scanning path is the key to ensure LPBF technology to achieve high quality forming.However,the existing LPBF processes almost adopt limited and fixed general process strategy,and it is difficult to consider the influence of structural characteristics on forming quality.It is an important measure to improve the forming quality of parts to realize the adaptive planning of process strategy by combining the significant structural characteristics of 3D model: overhang,thin wall,sharp corner,etc.This paper mainly studies the adaptive planning method of process strategy based on multi-feature recognition of 3D model.Combining algorithm development,numerical simulation and experimental analysis,the intelligent planning of laser scanning path based on feature constraint is realized.The main research work and achievements are as follows:(1)In view of the limitations of existing LPBF process path planning methods,which can not fully consider the influence of part structural characteristics on forming quality,a laser scanning path zoning method based on multi-feature recognition was proposed.By developing hanging feature recognition and thin-wall feature recognition algorithms,the 3D part model features structure area automatic identification,extraction and region segmentation was realized,in combination with commonly used method of path planning(parallel scanning,snake scanning,island scanning,etc.)to build the drive characteristics of the laser scanning path points regional planning model.(2)In order to analyze the influence of laser scanning path on forming quality of LPBF,thermal-mechanical coupled finite element analysis method was studied,and the numerical simulation of temperature field and stress field was carried out.By constructing the heat transfer control equation,Gaussian heat source,boundary conditions and material properties,the melting behavior of laser heat source,the evolution law of laser heat source on time,the change of stress field and the distribution of residual stress during the forming process were simulated and analyzed.(3)Numerical simulation and forming experiment were used to analyze the influence of different scanning strategies on forming quality of overhanging characteristic structures.The simulation results show that the deformation and residual stress are optimal when the scanning line strategy is parallel to the overhanging edge and there is only one scan line.Compared with the general scanning strategy,the deformation and residual stress can be reduced by 54% and 73% respectively.The forming test results show that this algorithm can effectively reduce the roughness of the overhanging surface and the residual stress of the overhanging structure.(4)The influence of different scanning strategies on forming quality of thin-walled characteristic structures was analyzed by combining numerical simulation and forming test.The simulation results show that when the scanning strategy with the longest dimension direction of the thin wall is 45° and the rotation between layers is 90°,the stress distribution is better.Compared with other scanning strategies,the directional stress along the long direction of the thin wall and the directional stress along the long direction of the vertical thin wall can be reduced by 10% and 4% at most.The results of forming experiments show that the roughness of feature boundary can be improved by zonal scanning path planning,but it can be reduced by changing the offset distance of feature boundary.