Reasearch On Wire And Arc Additive Manufacturing Process Of Supportless Overhang Structure

GMAW-based(GWAW,gas metal arc welding)wire and arc additive manufacturing technology has a series of advantages,such as compact structure,uniform chemical composition,high deposition efficiency and low production cost.It is widely used in additive manufacturing and repair of large-scale metal parts.Overhang structure is a very common component of complex parts.In non-metallic additive manufacturing,the forming of overhang structure is often realized by adding support.The design and manufacturing of support have been relatively mature,while the support of metal additive manufacturing is still in the preliminary research stage and faces many difficulties and challenges.Therefore,it is of great significance to study influencing factors of forming of the supportless overhang structure,to explore the maximum inclined angle of good forming of the overhang structure and to realize self-support of the steep inclined overhang structure.In order to solve a series of technological problems in the manufacturing process of supportless overhang structure,and to obtain a more universal process specification and processing strategy,this paper studied the overhang structure by means of molten pool observation,theoretical analysis and a series of technological experiments,so as to achieve a good forming of multi-angle inclined overhang structure and deposit a typical part of overhang structure.Firstly,the robotic GMA-based additive manufacturing experiment system is established.The forming quality of single deposition pass under different process parameters is studied,and the initial range of process parameters is obtained,and the matching formula between deposition current and deposition voltage is determined.The liquid molten pool in the deposition process of overhang structure is observed by the vision sensing system,and the flow phenomenon of molten pool is analyzed preliminarily.The multi-layer single-pass deposition model of supportless overhang structure is established,and the concepts of overhang angle as well as inclination angle of the welding torch are introduced,and the forming standard of overhang structure is established.The force analysis of the molten pool provides theoretical guidance for the selection of the inclined angle of the welding torch under the condition of small heat input.Under the condition of line energy 450 J/mm,when the overhang angle is 30 °,the inclined angle should be 41.41 °;when the overhang angle is 45 °,the inclined angle should be 61.25 °;when the overhang angle is 60 °,the inclined angle should be 80.04 °.Taking the 45 degree inclined overhang structure as the research object,the effects of deposition current,travel speed and the inclination angle of welding torch on the forming of the overhang structure are explored.According to the orthogonal experiment,the process parameters of the inclined overhang structure with different overhang angle are determined,and the processing strategy of the inclined structure with different overhang angle is proposed.The multi-layer single-pass inclined structure of 30 degree,45 degree and 60 degree is deposited respectively.The bridging experiment by horizontal overhang structure is designed and completed.Finally,the propeller model is selected as the typical part.According to the characteristics of the model,the surface slicing and dimensional path planning are carried out,and the robot program is generated.The propeller manufactured by GMA-based additive manufacturing has good forming quality and no obvious molten pool flow,and the effective thickness is above 5mm,which verifies the applicability of the process specification and processing strategy.