Research On Forming Control Of CNC Plasma Additive Manufacturing Of Honeycomb Structural Parts

Honeycomb structure has excellent mechanical properties and used in aerospace,rail transit widely.The traditional manufacturing method has many complicated processes,long manufacturing cycle,high dependence on equipment,and is difficult to meet the needs of social and economic development.Plasma arc additive manufacturing technology can not only simplify the process,shorten the cycle,reduce the cost,reduce the dependence of equipment,but also ensure the quality of the components.The representative cell of honeycomb structure was established to represent the geometric characteristics and all features of honeycomb structure.The honeycomb structure was simplified as a diagram by using the relevant theory of graph theory,and show that it doesn't conform to the characteristics of Euler diagram,and can't cover all the additive manufacturing path with one weld.Therefore,three path schemes were proposed according to the two path planning principles.and the advantages of each scheme were unified,determine the "gap and form" path to manufacturing the features in the same layer.Aiming at the technical difficulties of "segment lap" and "arc lap" in the path,two control strategies of "inverted trapezoid reciprocating" and "rotation compensation arc extinguishing" were proposed respectively to improve morphology between different layers.The final path of plasma additive manufacturing for honeycomb structure was obtained by synthesizing the "gap and form" path and two control strategies.In order to further explore the influence of droplet transfer on the forming morphology and solidification process in the add manufacturing,the model of droplet transfer in add manufacturing was established by using COMSOL,and the formation,falling,spreading and solidification of independent droplet were studied.On this basis,the "fixed-point stacking in the layer" and "remelting stacking between layers" were explored research.The influence of two drops in a single layer weld,the solidification process of the single layer weld,the remelting effect of the droplet on the front layer weld and the solidification process of the remelting weld were analyzed.According to the section shape and geometrical,obtained the rules of solidification and remelting solidification.The results of the model in good agreement with the experimentalresults,which provides a theoretical basis for the study of the forming process and solidification mechanism of plasma arc add manufacturing.The temperature field model of the first layer of additive manufacturing of honeycomb structure was established,using cell activation in COMSOL to deal with the deposit material.The double ellipsoid heat source was improved to "double ellipsoid compound moving heat source",so that it can not only translate but also rotate around its axis.The results show that the temperature distribution of the arc forming section is "Mango shaped";the weld pool area of the “arc-line” forming section increases first and then decreases,the temperature distribution returns to "ellipse" later;the angle direction of the front and rear weld formation affects the temperature rise speed and heat accumulation;the temperature distribution of single line forming section is greatly affected by the higher residual temperature of front weld,makes double high temperature area;The heat dissipation is the main component in gap forming section,the trend of temperature distribution is almost invariant.The numerical control plasma additive manufacturing system was built,and orthogonal experiment was used to obtain the range of parameters suitable for additive manufacturing.The effectiveness of two control strategies and the feasibility of path planning were tested.Finally,honeycomb structure with good shape and quality by numerical control plasma additive manufacturing was obtained.