Q.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.

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.

Effect of vibration frequency on biopsy needle insertion force

Needle insertion is critical in many clinical medicine procedures, such as biopsy, brachytherapy, and injection therapy. A platform with two degrees of freedom was set up to study the effect of vibration frequency on needle insertion force. The gel phantom deformation at the needle cutting edge and the Voigt model are utilized to develop a dynamic model to explain the relationship between the insertion force and needle-tip velocity. The accuracy of this model was verified by performing needle insertions into phantom gel. The effect of vibration on insertion force can be explained as the vibration increasing the needle-tip velocity and subsequently increasing the insertion force. In a series of needle insertion experiments with different vibration frequencies, the peak forces were selected for comparison to explore the effect of vibration frequency on needle insertion force. The experimental results indicate that the insertion force at 500Hz increases up to 17.9% compared with the force at 50Hz.

A new method for evaluating the normal rake angle and inclination angle on medical needles

Hollow needles are the most frequently used medical equipment. The design of a hollow needle that best enables medical procedures requires a better understanding of needle tip geometry. Calculating the cutting angles of a needle for a complex surface topology is difficult. This article proposes a new method based on non-Euclidean geometry for the analysis of biopsy needle tip. The method can be used to calculate the cutting angles on any pipe needle. To verify the validity of this method, the normal rake angle and inclination angle on four types of needles (bias bevel needle, cylinder surface needle, curved surface needle and Cournand-type needle) were investigated. It was found that calculation of the cutting angles was simple and convenient using this method, especially for the curved surface needles. Images of the cutting angles from the Cournand-type needles revealed that the smaller bevel angle ξ resulted in a higher normal rake angle α and inclination angle λ . As β increased, the range of the normal rake angle α became larger at first and then became smaller.

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.