| With the development of aerospace,defense industry,bioengineering technology and modern medicine,the demand for precision three-dimensional micro parts with characteristic size ranging from micron to millimeter,various materials,and high shape precision and good surface quality is becoming more and more urgent.The micro parts are mainly fabricated by micromachining technology,while the sizes for micro cutting tools,micro abrasive tools and microelectrodes involved in micromachining are generally below 1mm,and the smaller the size is,the more difficult the preparation is.Therefore,the successful preparation of micro cutting tools,micro abrasive tools and microelectrodes is very important for micromachining technology to realize the fabrication of micro parts and micro structures such as microgrooves and micro pores,etc.The multiple cutting and taper cutting technology of the low speed wire electrical discharge machining(LS-WEDM)make it can realize high precision and high quality machining of parts with up and down abnormalities and complex ruled surfaces,but,it can not manufacture parts with incomplete penetration surface or partial micro rotating structure.In order to make full use of the advantages of LS-WEDM machine tool,a rotary device is set up,and the LS-WEDM machine tool is firstly used to successfully fabricate micro cutting tools,micro grinding tools and microelectrodes,and solving difficulties of micro tools preparation in micromachining.In order to fully understand the technology and mechanism of the LS-WEDT process,the fundamental problems and practical applications of the LS-WEDT are studied by means of finite element simulation,geometric modeling and experiment.It is mainly reflected in the following aspects:(1)The material removal mechanism of the low speed wire electrical discharge turning machining(LS-WEDT)is discussed,and the generating principle of machined surface is analyzed,and formulas of residual height and residual area for machined surfaces are derived.A theoretical model of surface roughness for LS-WEDT is established from the geometric perspective,and the theoretical model is modified according to actual processing conditions and then verified by experiments.(2)The influence of main processing parameters on discharge crater size is obtained by the single pulse discharge temperature field simulation analysis of the LS-WEDT process.Then,on the basis of MATLAB,the surface morphology of LS-WEDT is simulated with different machining parameters and different processes,and then verified by experiments.(3)The surface integrity of the LS-WEDT is studied,and the influence of processing parameters on surface quality and subsurface damage is obtained.The surface characteristics of TC4 plane and rotary workpiece are comparatively analyzed,including surface morphology,discharge crater,debris,surface oxidation and alloying,hardness,remelting thickness,micro pores and micro crack distribution,and the relationship between surface characteristics change and the introduction of rotational motion is explored.(4)The cylindrical micro grinding tool substrate is fabricated by LS-WEDT method,and the prediction empirical formulas for erosion depth and diameter under different processes are obtained.Combining with the electroplating process,the diamond micro grinding tool with the diameter of 107.42?m,length of 1300?m and the mean absolute deviation of diameter of 0.637?m.Meanwhile,the complex spirals microelectrode with the length of about 1450?m,diameter of about 150?m,pitch length of 496.393?m and thread angle of 39.29 degrees also can be prepared by the LS-WEDT,more importantly,the pitch length,thread number,and thread angle of spirals microelectrodes can be controlled flexibly in LS-WEDT.In addition,the tapered cutting technology of LS-WEDT process is used to efficiently fabricate the conical surface microelectrode with the tip diameter of about 2.79?m and length of 326.64?m.(5)The simulation of micro milling.cutter fabricated by LS-WEDT method is realized by MATLAB,which realize the visual prediction predictability of the micro milling cutter and provide the theoretical basis for the parameter selection of practical processing.Various kinds of hard metal spirals micro milling cutter is fabricated by LS-WEDT including the single spiral micro milling cutter with the diameter of about 112?m,and the three spirals micro milling cutter with the diameter of about 175?m and the length of about 1300?m,the variable helical angle micro milling cutter and the six spirals milling cutter.Meanwhile,various special-shaped micro milling cutters are also manufactured by LS-WEDT including the taper micro milling cutter,the corrugated micro milling cutter,the ball head and the ellipsoid micro milling cutter,so solving actual difficulty of the fabrication of micro milling cutters.Besides,using the prepared cemented carbide micro milling cutter to carry out the microgroove milling and side milling experiments of DD5 single crystal nickel base superalloy,and evaluating the milling performance of micro milling cutter prepared by LS-WEDT method by analyzing the surface quality,burr,milling force and the cutting tool wear.The LS-WEDT proposed in this paper is used to successfully fabricate many kinds of spirals and special-shaped micro milling cutters,cylindrical micro grinding tools with high dimensional accuracy and spirals microelectrodes with complex structures,which broadens the application range of wire electrical discharge machining technology and provides new methods and ways for the preparation of micro tools. |
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