The continuously growing demand for high-precision complex-shaped parts combined with limited capabilities of conventional machining methods in their production have opened up high prospects for the use of Wire Electrical Discharge Machining (WEDM). The machining of ceramic composites with WEDM is an important area of highprecision machining. However, the high electrical resistance of such composites is a big problem, due to which WEDM of poorly conducting and semi-conducting materials cannot be monitored and controlled in the same way as that of electrically conductive materials. In particular, the adaptive control of the feed rate using monitoring of electrical parameters is no longer possible after the electrical conductivity of the workpiece material decreases to the level of semiconductors. This means that the development of monitoring and control principles and instruments for WEDM of semiconductor materials is critically important. In this work, after experimentally studying the physico-mechanical nature of EDM of semiconducting materials such as ceramic composites, recommendations for selecting the control criteria based on the vibroacoustic (VA) signal were developed. VA signals of the WEDM of semiconducting composite ceramics TiC+Al2O3 were measured to develop a more reliable method of preventing short circuits and wire electrode breakage than the conventional monitoring of voltage and amperage. We show that that the developed method is more efficient in detecting short circuits than conventional monitoring scheme and can thus be used as a foundation for the development of new adaptive control schemes of WEDM of semiconductor materials.
Rationalizing energy consumption in the Electrical Discharge Machining (EDM) efficiently saves energy and improves machining quality. Since the conventional methods for estimating useful EDM energy are based on theoretical heat transfer studies or empirical assessments of processing conditions, the development of an industrially applicable method for assessing useful energy is an important problem. Here we show that the performance of the EDM process is directly related to acoustic emission (AE). The effectiveness of the proposed method has been evaluated in experiments. As part of the execution of the experiment, AlCuMg1 workpiece was machined using a copper electrode with different duty cycles with pulse widths varying from 10% to 80%. For comparative analysis, the root-mean-square vibroacoustic signal in the range of 1-10 kHz and the root-mean-square of the discharge current were used. It was found that the amplitude of the vibroacoustic (VA) signal monotonically increases with the increasing EDM performance. The properties of the VA signal allows using the VA monitoring to assess the performance of EDM, i.e., to determine the fraction of energy spent on removing the workpiece material. The advantage of the proposed method of monitoring is that the control of useful energy is carried out using accelerometers installed on the parts of the technological system on the workpiece side. The distance from accelerometers to the workpiece being processed can be quite large that is convenient for performing experiments. In particular, in the high frequencies range, the obtained results are protected from mechanical interference coming from drives, hydraulic units and wire rewinding mechanisms. Such VA signals are shown to be important indicators of EDM efficiency because they are observed only if the energy fluxes reach the workpiece surface. This provides a more reliable indication of raising concentrations of electroerosion products that prevents short circuits and breakage of wire electrodes.
This paper discusses a new complex approach and an example of its practical application to solve the problem of improving the precision ceramics products and parts operational performance (ensuring high operational stability). The proposed approach consists of forming micro-texture in a ceramic product surface layer through vacuum-plasma deposition of conductive nanocomposite coatings based on a multicomponent thermally stable nitrides Ti-Al-Cr system as an auxiliary electrode in electrical discharge machining such as forming a specific microtexture in the surface layer, e.g., a combination of cavities, grooves, etc. This approach considerably improves the ceramic product surface layer characteristics, reduces contact surfaces' "ceramic product – counter face" adhesion and friction intensity, and ensures increased wear resistance and ceramic product operability.
Nowadays additive manufacturing becomes more and more popular. It depends on the results of last
achievements in developing of the new constructions for modern machine tools. One of the most developed AM
technology is SLM or SLS. About twenty years ago the technology of rapid prototyping started to grow up from
building prototypes and developed to real functional item production. Especially this becomes more important in
producing medical implants in the full accordance with individual digital 3D-model from metallic powder as
Ti6Al4V or CoCr. The additive technology gives the possibility to reduce additional steps in implants production
process as work preparation process, forwarding a work piece from one shop to another one, post treatment etc.
This approach is very topical to production of tooth, knee and coxal implants. This idea is realized in the
commercial SLM machines as EOS M280, SLM Solutions 125HL (Germany), Phenix systems PXS/PXM Dental
(France) (fig. 1).
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