Research On Forming Squarely Thin-walled Parts By Accurately Hybrid Laser Formation

The forming process of Direct Rapid Manufacturing of metal parts by laser is based on layered manufacturing, so the quality of forming parts’ surface and side surface is poor.Although the problem that the direct forming parts are not smooth has been solved by the hybrid forming process of “laser cladding + mechanical milling”, there are still problems of manufacture difficulty, low efficiency and waste of material. To solve above problems,the substractive manufacturing of laser milling is combined with the addtive manufacturing of laser cladding, and the accurately hybrid laser formation was proposed. 3D measurement system is used to collect and process the data of cladding parts’ salient points,then the results is fed to milling system to achieve accurate milling and closed-loop control of parts’ topography, and finally the rapid, efficient and accurate formation of metal parts is realized. The main contents are as follows:(1) The mechanism of laser milling on cladding parts was studied respecting to the characteristics of single track and multi-layer cladding parts’ geometry and material. The finishing effect of laser milling on cambered surface was analyzed from the aspects of the relationship between laser power density and laser irradiation’ position and the removal model of laser milling on cambered surface. Besides, the laser edge cutting model of cladding parts’ was also established.(2) Laser milling experiments on the surface and side of the single track and three layers’ Fe313 cladding parts were respectively carried out using pulsed fiber laser.Influential laws of dot spacing, power, pulse width and defocusing amount on the cladding parts’ surface roughness, deepness(width), and surface morphology was studied by single factor experiment. Besides, the range analysis of orthogonal experiment was adopted to analyze the influence level of different laser milling parameters on the cladding parts’ 3D roughness and deepness(width). It turned out that dot spacing plays the most important role both on surface deepness and side surface’s roughness, and power plays the most importantrole on side surface’s width. Further more, the laser milling parameters were optimized by the comprehensive balancing.(3) The data visualized processing software was further developed to CSV2DXF2.0based on surfaces’ salient points processing of 3D measurement system, which added the function of side surface’s data visualized processing. The function of surface’s data visualized processing was also kept in this software, so the 3D accurate milling of cladding parts and the closed-loop of forming parts was realized.(4) The squarely thin-walled part was formed sectionally. The salient areas were milled accurately by 3D measurement system and optimum milling parameters. After the milling was finished, the process of cladding-milling was repeated, and lastly the squarely thin-walled part with high surface quality was formed. The laser milling area’s microstructure of the formed part was refined obviously. The hardness in this area was increased, which means that laser milling is with the effect of re-melting and hardening.The hardness of hybrid forming part is higher than the direct forming part on the whole,which is particularly apparent in the area of microstructure refinement.Above researches show that the closed-loop control of forming parts’ 3D topography was realized by the technology of accurately hybrid laser formation, and the squarely thin-walled part with high surface quality was formed combined with the optimum milling parameters. Compared with other DRM, the work efficiency was increased, and the waste of materials and the production cost were reduced.