Temperature Field Simulation And Experiment On Small Hole Edm Drilling Of Composite Material ZrO₂/Cu

With the mature understanding of EDM mechanism gradually, it found that tool electrode materials have a significant impact on the EDM processing technique. Especially in recent years, as studies of materials spring up, various kinds of materials are used as tool electrodes. Researches on composite electrode come into being as the times require.At present, there are still some problems in the small hole EDM processing.Due to poor thermal resistance and low melting point of the copper material, the loss of common copper electrodes is large relatively in processing. Besides, with the increase of the depth of processing, accumulation of electrical erosion particles and undischarged ones in interelectrode gap lead to occurrence of the secondary discharge and tool electrode tip discharge easily. These problems not only reduce efficiency, but also increase the tool electrode wear itself and affect the shape precision of workpiece.Aiming at the defects of common copper electrode, this thesis proposes anew composite electrode with zirconia coating in the outer surface of the copper matrix by thermal spray technology through the summary of previous research results. The main property of the zirconia material is conductive in high temperature, but insulated under low temperature. By using this type composite electrode for machining of holes, realizing the purposes of reducing tool electrode loss and improving the precision of the hole shape.The main research contents are as follows:（1） This thesis makes an analysis of the zirconia coating characteristics theoretically, especially the reason of this semiconductor material property----conductive in high temperature but insulated under low temperature.（2） This thesis simulates EDM single pulse discharge temperature field distribution which occurs between the copper matrix and the zirconia coating by finite element analysis software ANSYS11.0, and verifies the temperature near the discharge point can reach up to the zirconia coating conductive temperature.This simulation provides the theoretical basis for the following experiments.（3） This thesis implements the comparative tests using ZrO₂/Cu composite electrodes and copper electrodes, and makes a comparative analysis of EDM process parameters such as processing speed, relative electrode wear rate,diameter expansion rate, taper etc. The results indicate that taper is reduced by10% maximally by ZrO₂/Cu composite electrode, compared with ordinary copper electrode, and boss height at the bottom of the blind hole decreases by42% dramatically when composite electrode is used to machine blind hole. Theshape accuracy of hole is improved and the surface roughness was improved slightly. Last comparison is made between Zr O₂/Cu composite electrode and Al2O3/Cu composite electrode.This thesis presents a new direction on composite electrode coating material zirconia semi-conductive coating, conductive in high temperature and insulated in low temperature, different from previous scholars researches conductive coating and insulated coating. In the future research, the materials of composite electrode coating can choose those semiconductor materials which not only have some ability of anti electric erosion, but also have the property of being conductive in high temperature and insulated under low temperature, in order to decrease the tool electrode wear loss and improve shape accuracy of small hole.