Papers by Keyword: CBN Grinding Wheel

Abstract: CBN wheel grinding performance on K9 glass is experimentally analyzed, which is using ultrasonic vibration assisted mechanical dressing, and dressing modes have different influences on grinding performance on the basis of the grinding surface morphology characteristics of K9 glass. The experimental results show that the CBN grinding wheel of vibration dressing mode has relatively large grinding ratio compared with ordinary dressing, and its microstructure on the grinding surface is strongly influenced by dressing modes and grinding speed.

Abstract: This study describes the theoretical basis of ultra-high-speed grinding. In addition, a new grinding machine tool whose maximum grinding speed can reach 450m/s has been recently developed, particularly, some of main components are basically discussed. Finally, this paper concludes with a presentation of current work and some future desirable plans in the area of ultra-high-speed grinding by means of the developed grinding machine tool.

Abstract: A set of precision vertical grinding experiment on WC-CO cemented tungsten carbide materials was carried out using cubic boron nitride (CBN) grinding wheel. Different grinding parameters such as rotation speeds of workpiece, feed rates and grinding depths were employed during precision vertical grinding. Surface roughness was measured for studying the grinding charateristics of WC-CO cemented tungsten carbide in this removal mode. Optimal grinding parameters were obtained by changing the process parameters. The research results have an important significance to improve grinding quality and efficiency for precision grinding cemented tungsten carbide materials.

Abstract: The grinding process is one of the most important finishing processes to obtain high surface quality. Nowadays, grinding is also considered as a high performance process with high material removal rates. Nevertheless, to avoid thermally-induced structural changes poses a major challenge for this manufacturing technology. Until now, the Finite Element Method (FEM) has been widely applied as a proper numerical technique to predict workpiece properties in machining processes. However, actual models in grinding are limited to conventional grinding processes with simple workpiece profiles and low table speeds. In this paper, finite element simulations are expanded to 3-dimensional (3D) models with temperature-dependent material properties and heat source profiles derived from experimental results, i.e. tangential forces. Both temperature simulation and measurement were conducted for deep grinding, pendulum grinding and speed stroke grinding in the table speed range of v_w = 12 m/min to 180 m/min and specific material removal rates of Q’_w = 40 mm³/mms. Overall, the simulation results show a good agreement with the measured temperature and surface integrity after grinding. This research indicates that a 3D FE model with temperature dependent material properties can predict realistic temperature fields in speed stroke grinding. Therefore, the experiment and measurement costs and time can be reduced by FEM simulation.

Abstract: The grinding process is one of the most important finishing processes in production industry. During the grinding process the workpiece is subjected to mechanical and thermal loads. They can induce thermal damages in terms of phase transformation due to critical temperature history. A holistic model helps to describe and predict the influence of these loads on the residual stresses in the surface layer. In this paper, a very promising approach using the Finite Element Method (FEM) to simulate the surface grinding process in terms of thermal and mechanical loads during grinding of hardened and tempered steels with vitrified bonded CBN grinding wheels is introduced. The investigations were conducted for deep, pendulum and speed stroke grinding. The change of workpiece material properties was modelled as a function of temperature and phase history. The results lead to the necessary time depending temperature distribution within the surface layer. Hence, the phase transformation can be calculated. The FEM software "Sysweld" was used to analyze the phase transformation kinetics. Hence, the size of the rehardened zone after grinding can be predicted. The evaluation of the FEM model with micrographs of ground workpiece specimens showed a strong correlation for different grinding parameters. Based on the understanding of mechanical and thermal loads as well as phase transformation kinetics in the surface layers the resulting residual stresses can be determined.

Abstract: Undeformed chip thickness is one of the most important parameters in grinding process, which is related to the entire abrasive grains in grinding simultaneously and changed periodically with time. Simplifying the geometric shape of abrasive grains ,the paper modifies the mathematic models of undeformed chip thickness by analytic method, establishes an universal calculation model of grinding force based on undeformed chip thickness, then optimizes the parameters of the model by restrictive random direction method according to the measuring experiments of the inter-grain spacing about CBN electroplated wheels and the grinding experiments of steel 55 during surface grinding, analyses the influence factors of the friction ratio on the grinding force. The results show that under the same grinding depth， both of the ratio and the grinding force will be decreased with the increase of velocity ratio VS/VW, but the ratio increases and the grinding force decreases with the increase of inter-grain spacing.

Abstract: The experimental research on CBN grinding wheel mechanical dressing assisted by ultrasonic vibration was carried out. Experimental results showed that ultrasonic vibration dressing is capable to improve surface topography and roundness of CBN wheel as other untraditional dressing methods. Compared with traditionally mechanical dressing, the counts of static effective grains of CBN grinding wheel dressed assisted by ultrasonic vibration increased clearly and it had clear relationship with the acoustic parameters and the dressing lead. The grains had a large protrusion height and kept good integrity after ultrasonic dressing. The technology of vibration dressing is able to prepare precisely the CBN grinding wheel.

Abstract: This paper presents a fractal analysis of the self-sharpening phenomenon of the grain cutting edges in cBN grinding. To clarify the self-sharpening mechanism due to the micro fracture of the cutting edges, the changes in three-dimensional profile of the cutting edges in the grinding process have been measured using a scanning electron microscope with four electron probes and evaluated on the basis of the fractal analysis. The fractal dimension for surface profile of the cutting edge formed by the micro fracture is higher than that of the cutting edge formed by the ductile attritious wear. Therefore, the complicated changes in shape of the cutting edge due to the self-sharpening can be evaluated quantitatively using the fractal dimension.

Abstract: In high and super-high speed grinding process, there is an airflow layer with high speed around the circle edge of the grinding wheel that hinders the grinding fluid into contact layer, namely, the air barrier effect. The speed of airflow layer is directly proportional to the square of the wheel speed. Quick-point grinding is a new type of high and super-high speed grinding process with a point contact zone and less grinding power. The edge effect of the air barrier is weakened because the thin CBN wheel is applied in the process. By the analysis of dynamic pressure and velocity distributions in the airflow layer around the wheel edge, the mathematic models of the flow and jet pressure of grinding fluid for effective supply in the process were established and the process of optimization calculation of the jet nozzle diameter for green manufacturing was also analyzed based on the thermodynamics and the technical character of quick-point grinding process. The quick-point grinding experiment for surface integrity influenced by grinding fluid supply parameters was performed.

Abstract: The balance precision of grinding wheel is a key technical parameter in ultra-high speed grinding process. The actual standard for the balance precision of rigid rotor is not fit for the thin ultra-high speed grinding system well. The unbalance factors affected on the ultra-high speed grinding wheel and its system were analyzed, and its effects on the machining quality in the process were also discussed. The theory and select principle of the balance precision for ultra-high speed grinding wheel system were studied. The test of dynamic performance was performed for the thin ultra-high speed CBN grinding wheel system whose structure was optimized. The groundwork to establish the standard of balance precision for thin ultra-high speed grinding system was offered.