Papers by Author: Cheng Zu Ren

Abstract: The deflection of Aluminum alloy thin-wall workpiece caused by the milling force leads to additional machining errors and reduces machining accuracy. In this paper, a set of experiments of milling thin-wall workpiece were carried out to study the deflection of thin-wall workpiece. The workpieces, with different types of material and different thicknesses, were machined on CNC machining center. The deflections of workpiece were measured by a three-coordinate measuring machine. Effects of Aluminum alloy material and thickness on deflection are discussed based on the experimental data.

Abstract: The machining of ceramic balls is one of the main difficulties of the manufacture process of ceramic ball bearings. This paper introduces a new grinding technique for green ceramic balls, the twowheels grinding technique. The sphering mechanism for the green ceramic balls ground with the technique was analyzed in theory, and the influencing factors were studied by experiment. The experimental research presents that the spherical deviation of the ground green ceramic balls can be improved to 0.02mm.

Abstract: In the paper, the Molecular Dynamics (MD) simulation model and the Finite Element (FE) analysis model were combined together to study the mechanism of the Electrolytic In-process Dressing (ELID) grinding. A 3-D MD simulation model for grinding monocrystalline silicon was established to acquire grinding force and its change laws, and an interpolation multinomial of grinding force was established on the basis of MD simulation result. A FE model for abrasives and the passivation film was established to calculate displacement of abrasives in the passivation film. The grinding force and abrasives displacement were iterated between MD simulation model and FE analysis model to obtain the displacement variation of the abrasives in the passivation film. The simulation result shows that, the uniform height of the abrasives in the contour of the grinding wheel is improved owing to the existence of passivation film in ELID grinding, it is related to the thickness of the passivation film, and processing quality in ELID grinding could be enhanced through controlling of thickness of the passivation film.

Abstract: In order to implement dynamic compensation for the wheel vibration of surface grinding machine, a micropositioning table with high stiffness and response frequency is designed. The micropositioning table is driven by three piezoelectric actuators with stiffness of 400 N/μm. Three capacitive sensors are utilized to form feedback control and flexure hinges are used to guide the moving part and preload for the piezoelectric actuators. The kinetics of the micropositioning table has been analyzed to understand the relationship of the control voltage and the posture of the moving part. Due to the coupling characteristic of the system, the decoupling control method is introduced to improve the performance of the table. Experimental tests are carried out to investigate the performance of the micropositioning table.

Abstract: The state of the passivating film is a key factor affecting ELID grinding. In the paper the state of the passivating film on the grinding wheel surface was characterized by the loop current, the strategies actively controlling the film state, discontinuous in-process electrolyzing and intermittent grinding were put forward, and the ELID grinding tests under the conditions of actively controlling of the film state and the traditional dynamic balance of the film state were respectively performed and contrasted with each other. It is indicated that by real-time monitoring of the film state with the loop current, the film state variation could be controlled to a narrow scope with the strategies of discontinuous in-process electrolyzing and intermittent grinding, as a result the ELID grinding kept at a fine quality and a high efficiency.