Research On Tool Electrode Wear Prediction Method In Shrouded Blisk EDM Die Sinking Machining

Shrouded blisk components are the most important parts of aerospace engines,and their manufacturing technology plays a vital role in engine efficiency and reliability.Due to its complex semi-closed space structure and highly twisted flow path,the EDM process with flexible tool electrode shape has become one of its most important machining methods.However,the inevitable tool electrode wear in EDM constrains the accuracy and efficiency of shrouded blisk machining.An effective wear prediction method can reasonably guide the replacement of the tool electrode,thereby achieving the balance between the electrode manufacturing cost and the workpiece processing efficiency under the premise of ensuring the machining accuracy of the workpiece.The current tool electrode wear simulation system is computationally inefficient and is only suitable for micro-sized electrodes.As the size of the tool electrode increases,the time cost of the simulation increases rapidly,even beyond the computing power of the normal computer,and cannot be applied to shrouded blisk,which have a normal-sized tool electrode with a multi-axis and rotation feed path.An "erosion model-electrostatic field model" decoupling architecture is proposed,aiming to reconstruct a new EDM tool electrode wear simulation system to solve the problems above.Firstly,the overall design of the tool electrode wear simulation system was conducted in the dissertation.A new simulation system architecture called "erosion model-electrostatic field model" decoupling architecture was proposed.In this architecture,the square uniform mesh was used for material erosion calculation;the triangular non-uniform mesh was used for electrostatic field calculation and discharge position determination.According to this,the two problems of the traditional system are solved.On the one hand,the computing power of the new system is no longer limited by the size of the tool electrode,and it can simulate the tool electrode wear with normal size.On the other hand,the new architecture completely decouples the internal functional modules of the simulation system,so that the feed motion of the tool electrode is no longer limited by other functional modules of the simulation system,and the rotation axis feed motion can be completed together with the line axis.Secondly,all the functional modules of the tool electrode wear simulation system were developed.Based on the "erosion model-electrostatic field model" decoupling architecture,a matched "dual mesh model decoupling" algorithm was developed.Based on the simulation system developed in this dissertation,it can be applied to the prediction of electrode wear of complex tools under normal size such as integral shrouded blisk.Thirdly,the problems of "mesh malformation" and "matrix in singular work precision" in finite element calculation were discussed,and the influence of electrode micro-edge shape and meshing state on finite element calculation was analyzed.The “edge fitting algorithm” was proposed,which eliminated the malformed meshes and optimized the convergence speed of the finite element numerical calculation.And increased computing efficiency of the simulation system by 60%.Lastly,the accuracy of the tool electrode wear simulation system was verified by the EDM experiment by using a square flat electrode and a 60° sharp electrode respectively.The tool electrode prediction of a shrouded blisk was completed.Compared with the experiment,an maximum prediction accuracy error of 8% was achieved,which occurred at the tip of the electrode with the smallest radius of curvature.