Research And Realization Of Forming Profile Accuracy Law Of MAG Deposition

Metal additive manufacturing technology is characterized by a high degree of automation,strong maneuverability and good forming quality.It was widely used in the fabrication and repair of customized metal components.Compared with laser beam and electron beam,arc welding has the advantages of low cost and high forming efficiency in metal additive manufacturing.In this thesis,the forming size and morphology features of metal active gas arc welding(MAG)in additive manufacturing were studied.With the aim of improving the accuracy of forming profiles,necessary size changing rules and outline geometrical models for MAG additive manufacturing were provided.First,the exploration experiment of single-layer single-bead deposition morphology under different parameter was carried out,and the range of process parameters with good forming morphology was obtained.Between the interval,use circumscribed central composite design method to establish the process parameters and the bead height and bead width of the response surface model,it studies the welding speed,arc voltage and wire feed rate on the influence of bead height and bead width,and further analyze the influence of the interaction of process parameters on bead height and bead width,to get optimum process parameters combination for different sizes of forming to provide the basis.Secondly,the forming morphology of single-layer single-bead deposition is studied.Based on experiment,the geometric model of single-layer single-bead deposition is determined by equal volume method,and verified by measurement.In order to improve the surface planeness of single-layer multi-bead deposition.the present overlapping model are summarized and analyzed.In view of the automatic shrinkage characteristics of molten metal under the action of liquid-gas surface tension in the deposition process,a parabolic overlapping model is proposed,and the critical center distance of two adjacent forming profiles is calculated.The overlapping profiles with different center distances are analyzed,and the reliability of the overlapping profiles is verified by measuring and comparing.Then,aiming at the characteristics of high forming of arc-starting end and low forming of arc-extinguishing end,the depositing mode of staggered distribution of arc-starting end and arc-extinguishing end was determined.In order to reduce the influence of accumulated error of multi-layer deposit height on the side-wall forming morphology,A prediction model of multi-layer and single-channel deposited layer height based on radial basis function neural network is established.The predicted results can be used as the important basis for optimize the welding torch lifting height between the layers.Finally,a geometric model of multi-layer multi-bead deposition is established based on single-layer multi-bead deposition in the center distance of critical value.Under the condition of constant parameters,the main reasons of unsatisfactory forming morphology were analyzed,and the optimization strategy was put forward.The reliability of the geometric model and the optimization strategy is verified by the experiment on the cuboid model.