Key Engineering Materials Vols. 359-360

Abstract: PVD (Physical Vapour Deposition) multilayer coatings were extensively used in cutting tools because of their relatively high wear and corrosion resistance, adhesion strength, hot hardness, and low coefficient of friction. The object of this study is to measure flank wear of dry cutting drills of different PVD coatings, including TiN, TiCN, and TiAlN by using drilling force experiments and machine vision technique incorporated with image registration technique. To obtain an optimal combination of cutting parameters quickly, we applied Taguchi method to plan the drilling experiment. The experimental results show that coating layer is the most important control factor for cutting and the TiAlN-coating drills generate least wear and thus has the longest tool life.

Abstract: In grinding process, chatter vibrations known as self-excited vibrations, become increasingly problematic and must be avoided. Firstly, experimental measurements of chatter vibrations in a numerical control (NC) grinding machine tool are introduced for the case of a special alloy workpiece being carried on. Then, frequency spectra of chatter vibrations are analyzed. The wavelet package transform technique is used to describe original chatter signals in the term of scaled energy of frequency bands. At last, fractal dimensions of the reconstructed signals in consecutive frequency bands of chatter vibrations are calculated. These results are helpful for understanding of the nonlinearity of chatter vibrations.

Abstract: Aiming at different grinding surfaces of hardened bearing steel GCr15, this paper made experimental research on detection method of surface roughness based on image technique. Adopting cold light source and five kinds of LED light sources, such as low-angle light, collimated light and coaxial light, we analyzed image characteristics of grinding surface under different processing conditions and found that there was a good correlation between standard deviation of gray variance and roughness of grinding surface. In comparison with the results from traditional surface roughness measuring instrument, we gained the corresponding relation between different grinding surface roughness and standard deviation of image gray variance. It was proved by calculating that they have a good correlativity.

Abstract: In this paper, the 3D morphology of a grinding wheel was modeled by the depth from focus. Firstly, the picture information of different heights was extracted by the up-down moving of the microscope. The operator Laplacian was adopted to distinguish the distinct and fuzzy areas in a picture. Then, the distinct image and height information was obtained. The information of height was distorted due to the occurrence of noise. In order to reconstruct 3D surface, a method based on Min/Max curvature flow was developed to remove noises. In the end, an abrasive grain in the image of a grinding wheel was segmented by the Mumford-Shah model. The results could be further developed to evaluate the worn status of grinding wheels. Introduction The examination of the wear of abrasive grain in the grinding wheel is very important for evaluation of performance of diamond grinding wheel. The three-dimensional (3D) reconstruction of grinding wheel topography can provide more information about wear of abrasive grains than common ways such as observation by optical microscope. Nowadays, there have been many techniques to be considered to obtain 3D data, for example, profilometry, the scanning electron microscope (SEM), the scanning laser microscope (SLM), stereo vision and so on. SEM is a powerful measuring tool, but the time needed for sample coating process and chamber air pumping is considerable. SLM is promising tool for 3D shape modeling, but still expensive for most of users. Stereo vision is simple and quick method to obtain the height information, but only the height of points which match in two corresponding images could been obtained. In this paper, a new method based on depth from focus (DFF) [1] is presented for 3D modeling. Compared with SEM and SLM, it is easy and not very expensive equipments are needed. Meanwhile, it can provide more real 3D model than stereo vision method. In order to measure the abrasive grains, a segmentation Algorithms based on Mumford-Shah model [4] is introduced to divide the grains from image of grinding wheel.

Abstract: The topography of the grinding wheel has a profound effect in analysis and predicting the finished surface roughness. In this paper, the statistical analysis is applied to establish a distribution function of the grain protrusion heights, and the 3-D simulating topography of grinding wheel will be identified. Through experiments, the generated grinding wheel topography is effective in predicting the finished surface roughness.

Abstract: Evaluation and measurement of form errors distributed on 3D ground curved surface are proposed due to the difficulty of processing measured points of 3D ground curve surface in comparison with axisymmetric curved surface. First form curved surface grinding is conducted by arc-shaped diamond grinding wheel, second ground curved surface is measured by contact measurement to obtain 3D measuring data, next transfer mode from CNC grinding to measuring reference frames is established, then effective and applicable 3D compensation arithmetic for probe sphere error is introduced, finally 3D form errors are investigated in connection with reference frame transfer and probe sphere compensation. It is confirmed that form error PV of is improved form 203 m / 8 cm2 is obtained by using reference frame transfer and probe sphere compensation, enhancing measuring accuracy by about 29 %.

Abstract: Remote control and fault diagnosis of ultrahigh speeding grinding is studied, which is based on the theory of rough set. Knowledge acquisition and reduction rule of fault diagnosis, realization method of remote control for ultrahigh speed grinding are studied, diagnosis model is established. Based on the theoretical research and ultrahigh speed grinder with a linear speed of 250 m/s, the remote control and fault diagnosis system of ultrahigh speed grinding is developed. Results of the system running show that the environment is improved, the mental pressure of workers is relieved and the efficiency is improved. At the same time, it proves that the ability to diagnosis and the accuracy of diagnosis for the ultrahigh speed grinding are improved and the time for diagnosis is shortened by applying rough set.

Abstract: 3Dfractal dimension and 2D profile fractal dimension distribution of the surfaces made by brittle or ductile grinding are calculated. From the calculated results of 3D fractal dimension, it can be found that the microtopograhpy of ductile ground surface is more exquisite than brittle ground surface and 3D fractal dimension Ds has inverse relation with the roughness parameter Rq. Through the analysis of 2D profile fractal dimension distribution in different ground surfaces, it is revealed that the topography of ground surface is changed with grinding parameters such as ground surfaces may have weakly or strongly anisotropic even isotropic features when different grinding parameters are adopted. Using fractal method to analyze the topography of ground surface is helpful to understand the generating mechanism of surface topography.

Abstract: In order to improve form cutter accuracy in grinding process, a closed-loop control system was designed to accomplish adaptive control of constant force in grinding process. Since it is a complicated dynamic process with severe nonlinear and much stochastic disturbance, fuzzy adaptive controller was used which can adjust parameters online. By measuring grinding force, characteristic information of grinding process was acquired. Regulation factor of feed rate is determined by grinding force ratio, and force deviation and its change rate are used as evaluation indexes. Thus, adaptive control of constant force in grinding process is accomplished. Simulation and tool grinding test indicate that the system has high precision and stability, and reduces cutter error efficiently.

Abstract: This paper develops a novel five DOF hybrid polishing kinematics machine tool in order to obtain more stable machining result in the elastic polishing on the free-form surfaces. Because the machine tool is a complex multi-body system that comprises many close-loop structures, jointing clearance becomes the important influence factor to its moving stability. The unified rigid multi-body and flexible multi-body dynamics equation of for the parallel mechanism of hybrid polishing kinematics machine tool is respectively built, which considers the influence of joint with clearance and applies the kinematics model of Newton second state. The result of analysis shows that the moving stability of the hybrid polishing kinematics machine tool is reduced due to the existing jointing clearance. However, the interior flexibility of the mechanism can reduce the shock effect of collision in the part of motion pair. It can improve the working stability of mechanism.