Cheng Zu Ren

A Study on the Mechanism of the Electrolytic In-Process Dressing (ELID) Grinding Using Molecular Dynamics (MD) & Finite Element (FE)

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.

Experimental Investigation on Honing of Small Holes

As a special kind of grinding, honing is a typical low speed precision machining process, which is of low grinding speed, little grinding heat and little thermal-residual deformation of workpiece, suitable for precision machining of holes in the precision couples of internal-combustion engine. Experimental investigation on effects of process parameters on honing efficiency of small holes was put forward in this paper to obtain economical machining efficiency. Circumferential speed, reciprocate speed and working pressure of honing stone are the key factors which affect the machining efficiency and quality of honing. Taking it as a case study the honing of the small middle hole of the valve seat of balancing valve couples of internal combustion engines, honing experiments were carried out in this paper to investigate the relationships of material removing rate in rough honing versus circumferential speed, reciprocate speed and working pressure in honing of small holes. The results show that in honing of small holes the material removal rate in rough honing increases with circumferential speed, reciprocate speed and reticulate cross-angle increasing but decreases when the two speeds exceed certain critical values, and the surface quality in finishing honing is improved by increasing circumferential speed.

Research on Intelligent CNC Platform Based on Hierarchical and Distributed Architecture for Grinding Machine

Grinding is a complex process and grinding automation based on CNC technology is developing forward flexibility, intelligence and integration. A CNC system for grinding machine is gradually becoming a complex controlling platform with all kinds of advanced functional units and interfaces. The trend of unlimitedly increasing functional modules and peripheral interfaces causes two unfavorable results. One is that more and more system resources are occupied, which weakens the ability of CNC system in real-time task controlling and rapid events responding. The other one is that the whole system is gradually falling into some chaotic and unstable expanding status. So it is necessary to add reasonable decentralization tactics to the architecture of integrated CNC system for a balance status of necessary functions and optimized performance. This paper aims at the establishment of an intelligent CNC platform for grinding machine, and brings forward the conceptions of hierarchical platform, decentralized control, sharable resources and disassembling tasks to realize the simultaneous satisfactions of completed functions, reliable performance and simple interactivity of an intelligent CNC system platform for grinding machine. Introduction Grinding is a complex process infected by all kinds of dynamic field machining conditions and grinding automation based on CNC technology is developing forward flexibility, intelligence and integration. CNC system for grinding machine is gradually becoming a complex controlling platform with all kinds of advanced functional units and interfaces [1]. Although there are many advantages about system integration such as united management, improved controlling ability, abundant interfaces and so on, the trend of unlimited increasing functional modules and peripheral interfaces causes two unfavorable results. One is that more and more system resources are occupied by the burdened process for coordinating and managing a great deal of task groups, which weakens the ability of CNC system in real-time task controlling and rapid events responding. When a system is assigned to strict real-time controlling tasks, any minor delay can cause unpredicted consequence or malfunction. The other one is that the whole system is gradually falling into some chaotic and unstable expanding status, that is, the scale and complexity are unexpectedly increased as the enriching process of new functional modules being integrated into the system, which makes the system more and more inflexible or overstaffed both in operating methods and peripheral interfaces [2]. This paper aims at the establishment of an intelligent CNC platform for grinding machine, and brings forward the conceptions of hierarchical platform, decentralized control, sharable resources and disassembling tasks to realize the simultaneous satisfactions of completed functions, reliable performance and simple interactivity of an intelligent CNC system platform for grinding machine. Dynamic and Floating Hierarchical Structure of CNC Platform Hierarchical system architecture is a well-chosen design scheme to resolve the complexity of highly-integrated CNC platform. But most of the current researches or applications on hierarchical system architecture are limited to the software fields, which can only solve the problem of complicated process controlling algorithm and massive information management, but can do little to Key Engineering Materials Online: 2004-03-15 ISSN: 1662-9795, Vols. 259-260, pp 715-719 doi:10.4028/www.scientific.net/KEM.259-260.715

Application of Complex Shifted Morlet Wavelet in Vibration Monitoring of Spindle Bearing of Crank Shaft Grinder

Grinder is one of key equipments in machining of crank shaft of automobile motor. So its vibration monitoring and fault diagnosis plays an important role in guaranteeing product quality and productivity. This paper builds an on-line vibration monitoring system for spindle bearings in which the complex shifted Morlet wavelet is adopted to realize the envelop demodulation and feature extraction so as to identify the type of fault. The main advantage of this method is that the center frequency and bandwidth are obtained not by user according to experience value manually, but by calculating for vibration signal. Therefore, it is very suitable for on-line monitoring and automatic fault diagnosis. The analysis of typical fault signal of rolling elements bearing shows that it can diagnose the fault accurately. Introduction The fault diagnosis of crank shaft grinder is critical for guaranteeing product quality and productivity and bearing fault is one of commonly encountered faults in grinder. Therefore, fault identification of rolling elements bearing has been the subject of extensive research. Different methods are used for detection of bearing defects, such as the shock pulse; envelop demodulation and acoustic emission method [1], etc. Among those, envelop demodulation based methods offer more reliable diagnosis potential, since they are based on more solid physical background. The traditional Hilbert transform is well established [2]. However, a major disadvantage of this method is that the selection of parameters is based on experience of the end user. So the complex shifted Morlet wavelet based demodulation is adopted in this paper to realize fault diagnosis of rolling elements bearing automatically. By analyzing of inner, outer race and roller fault signal, it will be concluded that this method can realize the auto-diagnosis of rolling elements bearing accurately. This paper is organized as follows. In section 1, a review of constant wavelet transform of discrete signal is given and the complex shifted Morlet wavelet is introduced in section 2. In section 3, the auto-envelop demodulation based on complex shifted Morlet wavelet is proposed to realize feature extraction of signal and the corresponding algorithm is given .In section 4, A monitoring system based on method proposed above is built to detect fault of rolling element bearing of grinder. By analyzing for signal sampled from grinder, the correctness of this method is testified. In section 5, the conclusions are given. Review of CWT of Discrete Signal Suppose that all constant signal x (t) satisfy the condition [3]

Electrolytic In-Process Dressing (ELID) and Super-Precision Grinding for the Ring Raceway of Ball Bearings

Electrolytic In-process Dressing (ELID) grinding technique is a newly developed technique based on electro-chemical machining and electrolytic grinding. The technology provides in-process dressing to super-abrasive wheels during grinding process to achieve a mirror surface in high efficiency and low cost especially on hard and brittle materials such as ceramics and hard alloys. ELID promotes the applications of hard and brittle materials in the new and high-tech fields. This paper describes the essential elements of ELID grinding system, the principle of ELID grinding and its applications. The feasibility of applying ELID to ultra-precision grinding for the ring raceway of ball bearings is discussed.

Shaping of Green Ceramic Balls and Precision Lapping of Ceramic Balls for Ceramic Ball Bearings

Ceramic balls are the key parts of ceramic ball bearings. The manufacturing quality and the cost of ceramic balls affect the performances and applications of ceramic ball bearings. In this paper, the machining efficiency, precision, surface quality and costs of ceramic balls are considered synthetically, the importance of the shaping process for green balls before sintering and the lapping process after sintering is discussed systematically, and several methods of shaping and lapping are compared. Introduction Ceramic ball bearings are new bearings with good performances. With the development of modern mechanical, aeronautic and astronautic industry, and the breakthrough of materials science, the ball bearings made from silicon nitride are widely used for high speed, high temperature, vacuum, radiation, running dry and strong erosion conditions because of their high-temperature resistance, erosion resistance, low expansion coefficient, low density, high hardness, etc. Ceramic ball is one of the key parts of ceramic ball bearing, and the performance and the cost of the ceramic balls are affected directly by the machining accuracy and efficiency of ceramic balls. But until now, in researching on the machining for ceramic balls, the lapping after sintering was paid great attention to, and the importance of the shaping process for green balls before sintering was ignored. In this paper, the shaping process for green balls before sintering and the lapping process after sintering are discussed systematically on account of the machining efficiency and quality. Importance of Shaping Process Machining Cost. The machining cost is one of the most important factors that determine the machining process is good or bad. The machining efficiency of ceramic balls is very low because the hardness of engineering ceramic materials is very high, and the materials are difficult to be machined, being a main reason that why the cost of ceramic balls is so high. Because of their high hardness, the efficiency of various machining methods for ceramic balls after sintering including newly developed one is not high. Before sintering, the ultra-fine power prepared for ceramic balls is compressed to shape green ceramic balls. The green ceramic balls have two important characteristics: (a) In actual process, the shape of molded green ceramic balls is irregular due to the limit of the technical conditions, and the spherical deviations and dimensional uniformity are bad. (b) Since the mechanical strength of green ceramic balls is very low, their machining efficiency can be very high. It can achieve twice the result with half the effect that the green ceramic balls have been shaped with machining because of their high machining efficiency. By shaping of green balls, the proper shape accuracy and dimension accuracy and dimensional uniformity of green balls can be achieved and the machining allowance of sintered balls can be reduced obviously, saving lots of human and material resources. This is very important to reduce the production cost. Key Engineering Materials Online: 2004-03-15 ISSN: 1662-9795, Vols. 259-260, pp 471-475 doi:10.4028/www.scientific.net/KEM.259-260.471

Three-Dimensional Simulation of Wheel Topography

Simulation of wheel surface topography is one key aspect of modeling the grinding process. A three-dimensional wheel topography model not only makes the simulated wheel topography more close to the real situation, but also benefits evaluation of wheel machinability and wears condition. This paper presents a physical model for simulation of three-dimensional wheel surface topography. Wheel structural components, grain shape, angle distribution of cutting edges, and the binding materials are considered in the model. Feasibility of the model is indicated by the simulation examples.

Numerical Simulation for Peripheral Milling of Aero-Aluminum Alloy Based on 3D FE Model

In this paper, an advanced 3D FE model was established using ABAQUS Explicit to simulate the process of milling aluminum-alloy 7075-T7451. Taking the end edge and the side edge of single flute into consideration, the model simulated the interaction between the spiral flute and wokpiece at full depth of cut. In addition, by defining automatic element deletion criterion and locally refining mesh, this model realized chip separating from workpiece without defining of cutting layer. The simulation results were compared with experimental data to verify the correctness of the simulation model.

The Experimental Investigation of Stone Wear in Honing

Honing is a finishing method by means of rotary motion and alternate motion between the honing stones assembled on the honing head and the workpiece. In honing process, the honing stone status is varying all the time and plays important role in cutting property. This paper analyzes the wear mechanism and the cutting property by cylindrical honing experiments. The wear mechanism is analyzed by the topography obtained by a microscope and the cutting property was investigated by two factors: material removal rate and honing force.

Study of Force Measurement in Honing

Honing is an abrasive machining process that produces a precision surface on a workpiece and widely used in manufacturing engine cylinder walls, compressor bodies, valve bodies, bearings, hydraulic cylinders and so on. Investigation and acquisition of the honing force could be used to investigate the honing mechanism and optimize the processing parameter. But it is difficult to measure the force during the honing process because of the limited honing structure. This paper presents a measuring system for honing force. It introduces the measure theory and the measure system. The whole measuring system is validated by experiment.