The surface grinding of the critical parts is the most important operation, which largely determines the product surface properties and its quality. In the context of automated production, efficient monitoring of this operation is a critically important task. In this work, we propose a new approach to monitoring of grinding: to simulate the processes of generating vibro-acoustic signals during grinding, to divide the working grains of the grinding wheel into sharp grains and low cutting ability ones. This division allows qualitatively predicting changes in the nature of vibro-acoustic signals accompanying grinding in different operational conditions, such as dry grinding and grinding with coolants, and the wear of the grinding wheel. The conclusions obtained based on the phenomenological modeling are confirmed by experimental studies showing that the vibration signal parameters adequately reflect the current state of the technological process and the wear of the grinding wheel. In this work, a new indicator for monitoring the grinding operation of products with high requirements to the quality of the machined surface was identified and evaluated. The proposed approach is shown to yield a more informative diagnostic indicator for finishing process compared to measurements of cutting forces, which are insufficiently efficient in the case of finishing operations with minimum allowance. The indicator was found to be efficient in the case of grinding of surfaces with roughness smaller than 0.4 μmm. The relevance of this indicator has been evaluated and proven in rigid grinding wheel-part-reference system, the use of which minimizes the probability of error.
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.
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.
Today, industry is accelerating the use of laser technologies. Laser technologies are one of the areas of material machining with high-energy energy flows. This actualizes monitoring of the performance of laser technologies, because it creates the preconditions for similar research in other areas. In this article, we present the results of experiments that make it possible to determine relationships between the vibroacoustic signals accompanying the action of laser pulses on a workpiece, and the intensity and duration of individual pulses. Analysis of experimental data has lead to identification of the main mechanisms of the formation of wave processes in the workpiece exposed to laser pulses and became the foundation for assessing the role of sublimation processes. The results obtained in this work can be used to develop monitoring system of laser processing for use in automated control systems.
The rapid development of new technologies employing laser, electron beam, electroerosion and other processes as the working ones requires new approaches to developing systems controlling operations being performed. However, these processes do not lend themselves to visual observation and do not allow the introduction of any sensors into the working process zone, which suggests that vibroacoustic diagnostics methods should be used. The article discusses obtaining information from a vacuum chamber under electron-beam action on thin films of reinforcing coatings. It is shown that the parameters of vibroacoustic signals accompanying the formation of new structures can be recorded with the help of flexible waveguides in the form of a wire drawn from a vacuum chamber to a plate with an accelerometer. The article presents and discusses monitoring the formation of intermetallic compounds under the influence of a pulsed electron beam on an aluminum plate covered with a thin film of a heat-resistant nickel alloy.
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