J.H. Zhang

Ultrasonic vibration electrical discharge machining in gas

Abstract A new method of ultrasonic vibration electrical discharge machining (UEDM) in gas is proposed in this paper. It is shown that electrical discharge machining (EDM) with ultrasonic aid can be achieved well in a gas medium. The tool electrode is formed into a thin-walled pipe, and a high pressure gas medium is supplied through it. During machining, ultrasonic vibration of the workpiece can improve the machining process. Molten workpiece material can be ejected from the base body of the workpiece with the aid of ultrasonic vibration and be removed/flushed out of the working gap without becoming reattached to the electrode. Selecting #45 steel and copper as the workpiece material and electrode material, respectively, experiments have been carried out, the results showing that UEDM is a method with a high material removal rate (MRR). The greatest advantages of this technique are lower pollution and a low electrode wear ratio.

Adaptive fuzzy control system of a servomechanism for electro-discharge machining combined with ultrasonic vibration

Abstract For electro-discharge machining (EDM), only when in the optimum state can the highest material removal rate be realized. In the practical machining process, the timely elevation of the tool electrode, which ordinarily occupies quite a lot of time, is needed to eliminate chipping. In this paper, an adaptive fuzzy control system of a servomechanism for EDM combined with ultrasonic vibration is studied. This control system can adjust the discharge pulse parameters in a timely manner, and also the gap between the tool electrode and the workpiece material, therefore, the machining state can be optimal, by which the EDM combined with ultrasonic vibration is improved and the machining efficiency is increased. In addition, a stimulation program is designed by means of Microsoft Visual Basic software.

Surface integrity and modification of electro-discharge machined alumina-based ceramic composite

Abstract Increasingly more applications require ceramic parts or components with good surface integrity. This paper attempts to study the surface integrity of electro-discharge machined engineering ceramics and their surface modification by ultrasonic polishing. Flexural strength is used for evaluating the effect of the two machining processes on the surfaces of the machined specimens. The distributions of the strength data are further analyzed by the Weibull statistical method to give quantitative measures of the surface integrity of the machined specimens.

Study on the diamond tool drilling of engineering ceramics

Abstract A method for drilling holes in engineering ceramics by using a diamond tool has been developed. In this method, a drilling tool rotates with fixed abrasives. The machining mechanism of drilling based on the fracture mechanics concept is analyzed, and a new theoretical model of the material removal rate is proposed. According to this model, the material removal rate increases in accordance with the increase of the static load applied, the rotational speed of the drilling tool, and the grain size of the abrasive. Selecting 99.5% Al2O3 ceramics as the workpiece material, experiments have been carried out. The results show that diamond drilling is an effective method for machining engineering ceramics.

Study on normal grinding force in ultrasonic aided grinding of sintered Nd-Fe-B permanent magnet

Sintered Nd-Fe-B magnet is the third generation rare earth permanent magnetic material. Contrasted with traditional grinding, the experiment of radial ultrasonic vibration aided grinding of sintered Nd-Fe-B permanent magnetic material was conducted. The effect on normal grinding force of grinding parameters was analysed respectively in the two grinding processes. Experimental results indicate, the radial vibration of workpiece reduced the normal grinding force to 1/3–1/4 of that in the traditional grinding and the discontinuous grinding mechanism caused by ultrasonic vibration is the main factor reducing the normal grinding force. In reducing the normal grinding force effectively, the process of radial ultrasonic vibration aided grinding is especially suitable for profile machining of sintered Nd-Fe-B permanent magnet. The radial ultrasonic vibration improved the stability of grinding and in the precondition of high machining efficiency, avoided edge collapse to a certain extent, assured the integrality of machining surface.

Numerical control system for the ultrasonic vibration assisted electrical discharge machine tool

A numerical control system for the ultrasonic vibration assisted electrical discharge machine tool is developed, based on the Windows 98 operating system, industrial PC, PMAC-1 four axes controller and servo-motor. Compared with the traditional control system, it provides better man-machine interaction and integration. The design based on modules makes it flexible and easier for the user to operate.