Simulation and assessment of diamond mill grinding wheel topography

The topography of grinding wheel has a remarkable effect on grinding process. In this paper, the topographies of two mill grinding wheels with different grain sizes were measured by using an Olympus confocal scanning laser microscope. Kolmogorov–Smirnov normality tests were carried out to obtain distribution characteristics of abrasive grains. The test results indicate that the surface of grind wheel is of non-Gaussian nature. Consequently, a non-Gaussian statistical model was proposed to simulate the mill grinding wheel topography. Simultaneously, some parameters of “Birmingham 14” were introduced to assess the grinding wheel surface quantitatively. Simulated profile of the grinding wheel is found to correspond well in appearance with that of the actual grinding wheel.     

基于双目图像的砂轮地貌检测

砂轮地貌的准确检测可以反映砂轮磨粒的出露高度和分布情况等,对于揭示砂轮的磨削机理发挥重要的作用.鉴于传统的砂轮地貌检测方法存在种种缺陷,提出了一种基于双目图像的磨粒出露高度检测方法.该方法采用灰度模板匹配算法,通过优化模板尺寸进行图像匹配,可以估算出磨粒的出露高度.试验结果令人满意,磨粒出露高度估算误差小于5%.     

Modeling and simulation of grinding surface topography considering wheel vibration

Grinding is an important means of realizing precision and ultra-precision machining. Vibration caused by an unbalanced grinding wheel in grinding process has a significant impact on the quality of workpiece surface. However, the effect of wheel surface topography and/or the relative vibration between grinding wheel and workpiece are not considered in most researches. Taking the relative vibration between grinding wheel and workpiece into account, alongside the abrasive grain trajectory equation, a new analysis and simulation model for surface topography of the grinding process is established. The model for the topography of the grinding wheel surface is first studied, and subsequently, a new simulation model for surface topography of the grinding process is proposed. Case studies are performed at the end, and the influence of grinding wheel vibration amplitude, wheel grit number, as well as grinding parameters on the surface waviness and roughness is discussed. The simulation results could be used to optimize the actual grinding process to improve the ground surface quality or predict the surface topography by given grinding parameters.     

Reduced models of grinding wheel topography and material removal to simulate dynamical aspects in grinding

Increasing competition and short product life cycles make it necessary to optimize and evaluate the outcome of manufacturing processes. In tool grinding, models for the final workpiece geometry and cutting forces are of particular interest. To establish a valid general grinding model, we investigated the cutting process and the influence of local grinding wheel engagements on the material removal. We consequently developed models of material removal and grinding wheel topography, which capture the main correlations in grinding. In combination, temporal cutting forces and final workpiece geometry are predictable and are in excellent agreement with experimental data. The introduced models are valid for grinding in general, since they are solely based on the geometry and process parameters, and hence are applicable for manufacturing process optimization.     

Effects of dressed wheel topography on patterned surface textures and grinding force

The camshaft is a crucial component of an engine’s valve train. This paper devotes to the experimental studies of the performance of laser surface textured (LST) camshaft. The first part experiment was carried out on the block-on-ring tester to investigate the tribological behaviors of textured surface in line contact. The area density of the textured dimples was in the range 3–40% with depths 5–24 μm and diameter 70 μm. The friction coefficient and wear tracks were analyzed to confirm the optimum textured patterns. After that, the local LST cams (textured on the lifting region) were further tested in a single-cylinder diesel. It was found that after 300 h durability test at the rated speed and load, the total lifting loss of cams decreased nearly 34.4% in maximum. In addition, the performance of the engine was not affected evidently. The enhanced lubricity and local hardening were two mechanisms for highly promoting the anti-wear property of the LST cams.     

A precision grinding method for screw rotors using CBN grinding wheel

Aiming at the high precision machining of screw rotors, a new grinding method for screw rotors using cubic boron nitride (CBN) grinding wheel is presented in this paper. Small electroplated CBN grinding wheel is firstly used to grind screw rotors. The mathematical model for the axial profiles of CBN grinding wheel is developed based on gear engagement theory. Taking the backlash of screw rotors and the coating thickness of CBN layer into consideration, the modification of the base body of the wheel shape is introduced into the design of the CBN grinding wheel. Wire cut electrical discharge machining low speed (WEDM-LS) was used to machine the base body of the CBN grinding wheel. The formed turning tools of the base body of CBN grinding wheel using WEDM-LS and the wheel shapes of CBN grinding wheel using the formed turning tool were performed. The CBN grinding wheels for the screw rotors were made to verify the validity and effectiveness of the presented method. The electroplated CBN grinding wheels were used to machine the screw rotors, and the machining experiments were performed. The data obtained in the experiments reach the fifth class of Chinese Standard GB10095-88.     

Identification of grinding wheel wear using random process analysis

Profiles of grinding wheel surfaces have been analysed in terms of a random signal using virtually on-line instrumentation. By this method the contribution of the three acknowledged modes of grinding wheel wear, attritious, grit fracture, and bond-post fracture (or grit dislocation), to overall wheel wear can be readily identified.Results of tests under varying conditions of controlled force plunge cylindrical grinding are reported in detail.     

Measuring wear of the grinding wheel using machine vision

This paper proposes a new method for measuring grinding wheel contours using machine vision. The vision-aided measuring system comprises a CCD coupled with a telecentric lens, back lighting board and frame grabber. Measuring the image of the specimen with a grinded gap substitute directly captures the image of the actual grinding wheel. Using this method makes the 3 D of the topography of the grinding wheel into the 2 D of the contour of the grinding wheel. This method significantly simplifies grinding wheel wear measuring procedures compared with the traditional methods. Therefore, the presented paper provides a new method to improve efficiency and cost on measuring wear of the grinding wheel. The results show that this developed system achieves a repeatable accuracy of ±3 μm for the measurement of the grinding wheel contours.This paper has not been published elsewhere nor has it been submitted for publication elsewhere.     

Study on precision grinding of screw rotors using CBN wheel

With increasing demands for high-speed and high-precision machining technology, CBN shape grinding is an effective means in the field of precision machining for screw rotors. Aiming at the high precision machining of screw rotors, a mathematical model for the axial profiles of the CBN wheel for machining screw rotors is developed based on theory of gear engagement. Small electroplated CBN wheel is firstly used to grinding screw rotors. Taking the backlash of screw rotors and the coating thickness of CBN layer into consideration, the modification of the base body of the wheel shape is introduced into the design of CBN wheel. For reducing the tooth profile errors of screw rotors induced by mounting errors and wears of CBN wheel, a mathematical model of the error analyses is established and the influence curves of the profile errors affected by mounting errors and radius error of grinding wheel are proposed. The electroplated CBN wheels for the screw rotors are made to verify the validity and effectiveness of the presented method and the machining experiments were performed. Results of this study reveals that the method proposed in this paper can be used as the precision grinding of screw rotors.     

Three-dimension surface characterization of grinding wheel using white light interferometer

Wyko NT9300 white light interferometer was employed to measure the surface topography of 60# and 120# alumina grinding wheels. The correlation of wheel topography and its performance was characterized through the employment of three-dimensional (3D) surface characterization parameters. Eight parameters from the ??Birmingham set?? were used to characterize the performance of grinding wheels, in items of grit density, grit sharpness and chip space. The effect of sampling interval on the 3D surface parameters was analyzed and the optimal sampling interval was selected to calculate the 3D surface parameters of grinding wheels.     

Influence of straightening conditions for a grinding wheel on the acoustic-signal intensity

Russian Engineering Research -     

Evaluation of grinding wheel performance

Experiments were carried out on a horizontal surface grinding machine under dry plunge-cut conditions to evaluate grinding wheel performance in the grinding of steels of various hardnesses. It was found that an optimum wheel grade exists which gives the highest grinding ratio and this optimum grade is different for different materials. There is also an optimum grain size for a particular work material. However, this optimum grain size did not vary for the three materials tested. In all cases grain size 46 gave the best performance.     

Fluorescence lifetime imaging using a confocal laser scanning microscope

The implementation of a fast fluorescence life-time imaging method in a confocal laser scanning microscope is described. The set up utilizes a low-power continuous wave (CW) argon ion laser equipped with an electro-optic chopper producing nanosecond pulses with a repetition rate up to 25 MHz. A time-gated detection technique enables the measurement of the lifetime of a pixel in 40 μs. The first confocal fluorescence lifetime contrast images are presented. Application of fluorescence lifetime imaging in multilabelling experiments for discrimination between different labels with overlapping emission bands, for probing the local environment of a fluorescent molecule, and for quantitative fluorescence are discussed.     

Observation of the retina using the tandem scanning confocal microscope

A tandem scanning confocal microscope (TSCM) is currently being used to obtain high-resolution images of the human cornea in vivo. Advantages of confocal microscopy for in vivo imaging include optical sectioning and increased contrast through removal of scattered light. We have adapted the TSCM to view the retina in vivo by constructing an applanating lens and fitting the microscope with an imaging-intensifying camera of increased sensitivity. The microscope uses a spinning disc with 40,000 holes, each of 30 microns diameter, and a 100 W mercury arc lamp light source with a 455 nm long pass filter. The applanating lens is composed of three elements, two of which are movable for focusing. Images of a rabbit retina were obtained in vivo revealing the nerve fiber layer and blood vessels around the optic disc. The power density at the retina was calculated to be 3 mW/cm², which is well below the power levels of a direct or indirect ophthalmoscope. Magnification of the retinal image was approximately 60x and a 1 mm wide area of retina was in view. This prototype TSCM system demonstrates that images of a retina in vivo are obtainable with confocal microscopy and that the sharpness is comparable to standard fundus camera photography. Further modifications to improve the light level and alterations in the design of the objective should improve the quality of the images obtained and achieve the enhanced resolution of which, in theory, the confocal microscope is capable.     

Evaluation of grinding wheel loading phenomena by using acoustic emission signals

In the industrial manufacturing field, machining is a major process. Machining operations involve grinding, drilling, milling, turning, pressing, molding, and so on. Among these operations, grinding is the most precise and complicated process. The surface condition of the grinding wheel plays an important role in grinding performance, and the identification of grinding wheel loading phenomena during the grinding process is critical. Accordingly, this present study describes a measurement method based on the acoustic emission (AE) technique to characterize the loading phenomena of a Si₂O₃ grinding wheel for the grinding mass production process. The proposed measurement method combines the process-integrated measurement of AE signals, offline digital image processing, and surface roughness measurement of the ground workpieces for the evaluation of grinding wheel loading phenomena. The experimental results show that the proposed measurement method provides a quantitative index from the AE signals to evaluate the grinding wheel loading phenomena online for the grinding mass production process, and this quantitative index is determined via some experiments in advance in the same grinding environment to help the monitoring and controlling of the grinding process.     

Experimental study on ultrasonic-assisted grinding of micro-structured surface on silicon carbide using small diameter grinding wheel

Journal of Mechanical Science and Technology - As an effective machining method for hard and brittle materials, ultrasonic-assisted grinding (UAG) was employed to manufacture microstructures on SiC...