Research On The Wire Filled Rapid Prototyping Process Based On Micro-plasma Arc

Micro-plasma arc rapid prototyping (MPA-RP), using plasma arc less than30A asheat source and welding wire as fill material, achieve the goal of metal forming directlybased on the principles of layer by layer accumulating. In this paper, in order tooptimize forming process and improve accuracy, the layer dimension predicting modelswere set up and the pass forming process based on the one dimension was studied andoptimized. Finally, The path road on the purpose of least shaping by the way ofnumerical simulation was optimized to ensure the forming quality and precision.First of all, a micro-plasma rapid prototyping platform was designed and realized.The whole system consists of four parts: three-dimensional moving device, weldingdevice, liner structured light sensor and the relating software. Making sure the matchingrelations and ranges of wire feeding speed v2, current I and arc moving speed v1. Also,the temperature between layers during the multilayer forming was determined as100℃.The traditional quadratic regression method was used to establish the predictingmodel of layer size for the multilayer forming with the above three process parametersand the number of levels n. Using the statistical tests to make sure the effective ofpredicting model. Based on the upon studies, The multilayer forming tests with thesame width and changing process parameters was finished. The Experiment showed thatthe maximum deviation was7%which occurred in the first layer. Model predicting fitsthe actual size favourably.A single layer multi-pass model was set to analyze The influence of aspect ratio λand distance l on the overlapping ratio η and forming quality. Both theories and lapexperiments showed that the higher aspect ratio λ was better for improving the moldingquality, also, the surface flatness improved largely when λ was higher than4. Theimpact of λ on forming was due to both different heating regions and different states ofmelted metal filling. When the ratio λ increased, both the changing surface tension andthe heating regions can lead to the improvement of surface flatness.In order to optimize the forming path road and reduce the shaping deformation, theinfluence of stacking direction between layers and passes on the inner temperature,residual stress distribution and buckling deformation was studied by the MSC.Marcsoftware. When forming in different paths, different kinds of heating character wouldlead to the different residual stress distribution. That’s the reason why it showeddifferent kinds of shapes at last. The research showed that alternating direction wasbetter than the same direction in layers and passes.Finally, combined with the actual forming process, both multilayer stacking andmulti pass stacking experiment was finished. It shows that the optimized forming path combining with the actual forming process reduced the forming shaping and ensured theaccuracy dramatically.