Study On Process Of Overhanging Structure Based On Selective Laser Melting

Since selctive laser melting(SLM) can form the metal parts by metal powder and the metal parts are the final product which can be closed to 100% of the density without further machine processing.So SLM is called one of the most potential technologies in AM..The forming of the overhanging structure has been a difficult problem for this industry because of its defects such as warping, slag, collapse and so on.This paper mainly aimed at forming a overhanging structure, study the type and the added method of support structrue. For the complex structure support which is difficult to remove, this paper give a detailed description of forming it through process optimization method.The energy transfer in the process of selective laser melting is analyzed based on the forming mechanism, and the results show that the laser energy absorption of powder is only related to the laser wavelength and powder species.Besides the melt pool and heat distribution has a great influece on the deformation of parts. Start from Gaussian energy distribution model, the relationship between the laser melting depth and various laser processing parameters was obtained, and the conclusion is the laser energy density of selection has a great influence on laser melting depth.Then discuss the support types and the methods of adding support. For different overhanging structrue, it can flexibly select the type of support structure,set up the support density and contacted tooth type. Besides the calculation method of the critical angle which can form overhanging structure is analyzed by the theoretical formula.Again through designing experiment, analyze the influence of laser power, scanning direction of processing on the morphology and sample ball effect,then finding the selecting of the first layer’s process parameters has great influence on forming the overhanging structrue sample. With the layers increase, the influence on the dimensional accuracy is also getting smaller and smaller, and the selection of scanning method for successful forming the overhanging structure also has great significance. So it put forward that the overhanging structure can be forming without support by using layer changed process method. It is found that the density of the formed part can be improved while the dimension accuracy of Z is guaranteed.Finally, according to the research results, the porous lattice structure with overhanging structure is formed successfully. After measurement and experiment, compared with the processing overhanging structure of traditional fixed parameters, this processing method has greatly improved in the Z dimensional accuracy and density.