Advances in Machining & Manufacturing Technology IX

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Authors: Xin Wei, Hui Yuan, Wei Xiong, Xiao Zhu Xie
Abstract: This paper studied the effects of the off-process conditioning parameters on the pad performances. The pad conditioning was evaluated based on the measurement of pad removal rate, the observation of the conditioned pad surface. The performances of conditioned pads were evaluated also by the material removal rate (MRR) and the surface roughness of polished wafers in the CMP experiments of LiTaO3 crystal wafers.
Authors: Bao Guo Zhu, Zhen Long Wang, Bao Xian Jia
Abstract: Developed with micro technology, the microelectrode is the key manufacture technique. The micro electrical machining, mainly including micro electrical discharge machining (EDM) and electrochemical machining (ECM), is one of the important technologies of microelectrode fabrication. Firstly, the microelectrode was fabricated with a counter block of EDM while the cylindrical tungsten electrode fed along radius and its axis. Then the fabrication technology of ECM was also introduced. The pulses power supply and the non-passivation electrolyte were used. The cylindrical tungsten electrode also can be served as the probe of the scanning probe microscopy, which fabricated by ECM. Through comparisons, the surface roughness, machining efficiency, and machining capability of the microelectrode fabricated by ECM are better than those of the microelectrode fabricated by EDM, but the shape and the microhardness are worse than those of the microelectrode fabricated by EDM. Both of them can fabricate the cylindrical tungsten microelectrodes with several micrometers diameter.
Authors: Zhen Long Wang, Wei Liang Zeng, Qiang Gao
Abstract: Micro electrical discharge machining (EDM) with block electro discharge grinding (BEDG), is explored and assessed as a method for developing micro electrode, for wire electro discharge grinding (WEDG) has shortcoming of low working efficiency, especially in the case of micro machining. For fabricating micro electrode by BEDG, mechanics of initial clamping errors are analyzed, the technology of electrode movement is proposed to compensate the clamping errors and control the finish size of micro electrodes. On the basis of a great deal of experiments, the effect of working voltage on machining efficiency has been found out and been analyzed theoretically, threshold value of working voltage is determined to be about 30V.As shown by result with the technology, at a high machining speed, the minimum diameter of micro electrodes reaches 3*m, its slenderness ratio is more than 5.
Authors: Pai Shan Pa
Abstract: A most effective design system and an advantage of low cost equipment using synchronous processes of electrochemical finishing and burnishing for a freeform surface following turning machining is investigated. The proposed design process uses a feeding finish-tool instead of the mate electrode as in conventional ECM. Hence higher electrical current is not required when the effective design electrode is used to reduce the response area. Through simple equipment attachment, electrochemical finishing can follow the traditional turning on the same machine. The controlled factors include the chemical composition and concentration of the electrolyte, die material, and rotational speed of workpiece. The design finish-tool is primarily discussed among the factors affecting the synchronous processes of electrochemical finishing and burnishing. The experimental parameters are initial gap width, flow rate of electrolyte, current rating, feed rate of finish tool, pulsed period, and the evaluation of different process features. The use of large electrolytic flow rate is advantageous to the finish effect. High rotational speed of the finish tool produces better finish. The finish effect is better with longer off-time because discharge of finish dregs becomes easier. Higher current rating with quicker feed rate of finish tool effectively reaches the fast improvement of the surface roughness of the workpiece is recommend in current study. The effective design finish-tool with an electrode of a globe-form and a burnishing tool of a pin-form have an optimal value for higher current density and provides larger discharge space, which produces a smoother surface. The synchronous processes of electrochemical finishing and burnishing just needs only a short time to make the workpiece smooth and bright and saves the need for the precise process of traditional machining is recommended for the finish process of the freeform surface.
Authors: Yong Feng Guo, Guan Qun Deng, Ji Cheng Bai, Ze Sheng Lu
Abstract: Advanced engineering ceramics are more and more widely employed in modern industries because of their excellent mechanical properties such as high hardness, high compressive strength, high chemical and abrasive resistance. These properties limited the machining to the insulated ceramics. This paper investigates the electrical discharge machining (EDM) of ZrO2-based ceramics by assisting electrode method. The theory of assisting electrode method is introduced. The machining phenomena under different electrical parameters were studied. The material removal mechanisms change with the increase in the power of single pulse. Some work-pieces have been machined successful through the assisting electrode method.
Authors: Xiao Hai Li, Zhen Long Wang, Jun Fa Wang, Xin Rong Wang
Abstract: A new process of fabricating microstructures through micro electrochemical milling (micro EC milling) is proposed. By utilizing side wall of simple micro tool electrode rotating at high speed like micro mechanical milling and controlling the movement track on NC three-axis feed worktable, microstructures with high precision can be milled by micro-ECM under high-frequency short-pulse current. Micro EC milling can greatly improve the machining status in the tiny machining gap and thus make machining stable by simple rotary column electrode. The influence factors on the accuracy of micro-EC milling were investigated through process experiments, such as feed speed, machining voltage and kind of electrolyte. The process of the NC generating micro-ECM integrating CAD/CAM technology is studied. G code for machining complex microstructures can be generated by the universal CAD/CAM of traditional milling based on UG software. Last, Microstructures with complex shape were milled by this process, for example the micro bend beam with width of about 50μm, and its aspect ratio is about 6.
Authors: Ying Xue Yao, Li Qun Li, Jian Jun Xi
Abstract: The effect of technological parameters on MAO ceramic coating were investigated through the technique of micro-arc oxidation (MAO) on TC4 titanium alloy and. Microstructure and morphology of coatings were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The result shows that electric parameters and compositions of the electrolyte have notable effects on the growth of MAO ceramic coatings. The cathodic and anodic voltage rise gradually with the oxidation time increasing. The growth rate of ceramic coating is fast at the beginning, and then turns slowly. The ceramic coatings can be divided into three layers from interior to exterior, such as the transition layer, the dense layer and the porous layer. The coating is mainly composed of rutile and anatase and combined with the substrate firmly. The ceramic coating’s composition in inner and outer layers appears quite different. The ceramic coating on titanium alloy is of excellent performance on anti-attrition and anti-corrosion.
Authors: Hong Bin Liu, Da Ping Wan, De Jin Hu
Abstract: The processing parameters of laser texturing are linked with the wear property of roller surface based on the relationship between the fractal parameters and surface roughness. The influence of laser power density, scanning speed and pulse width on the roughness is analyzed though experiments. The effect of fractal parameters on the wear rate of the roller is analyzed with fractal geometry model for wear prediction. Condition of achieving engineering surface with optimal fractal dimension is presented and the expression of the optimal fractal dimension is derived. It shows that the roughness of laser textured surface and normalized wear rate are mainly determined by laser power density and fractal dimension, respectively. Moreover, to get the textured surface with smallest nominal wear rate, processing parameters of laser texturing, especially the laser power density, should be controlled properly besides the material properties of the roller. The result will provide guidance for the processing.
Authors: Li Jun Yang, Yang Wang
Abstract: Laser forming of metal sheet is a forming technology of sheet without a die that the sheet is deformed by internal thermal stress induced by partially irradiation of a laser beam. In this paper, the bending behavior of common stainless steel 1Cr18Ni9 sheet is studied after being irradiated by straight line with a Nd:YAG pulsed laser beam. The aim of the investigation is to find out the relationship of the physical behaviors of heat affected zone (HAZ) with the pulse parameters of the laser. Through the analysis of the fundamental theory of pulsed laser affected, this paper shows the affected characteristics of metal sheet with pulsed laser forming. The results show that the microstructure of HAZ of pulsed laser scanned is layered, and the micro-hardness is improved than that in matrix. The microstructures show that the deformed grain structure is inhomogeneous, that caused the grain sizes and grain orientations in HAZ to become different. By qualitative analysis of experimental result, the conclusion obtained may provide basis for theoretical investigation and possible industrial application of laser forming process in the future.
Authors: Xia Ji, Jian Zhong Zhou, Hua Feng Guo, Da Peng Xu
Abstract: This paper presents an experimental investigation on the metal components fabricated by laser cladding. In the present study, two process of laser cladding were conducted, that is pre-placed powder cladding and coaxial powder-feed cladding. The effect of processing parameters was studied and optimum set of parameters for the superior surface quality was established by employing the orthogonal design. The fabricated components were subjected to metallographic examinations and micro-hardness measurement. Results indicated that the microstructure of coaxial cladding components was finer than pre-placed powder cladding components. The micro-hardness of the fabricated specimen along and vertical the scanning direction were measured using a HVS-1000 micro-hardness tester with a 200 g applied load. Analysis of the physical properties provided further evidence of differences in micro-hardness produced by different process conditions, and the average micro-hardness value of pre-placed power cladding layer was lower than the coaxial powder-feed cladding layer.

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