Image processing of the grinding wheel surface

Identifying the situation of grinding wheel wear and loading is a very important issue for high-efficiency grinding operations. This paper presents a new method that detects and identifies the chip loading and cutting edge wear of a grinding wheel using the image processing toolbox of the MATLAB package. The different optical characters of the metal chips and the abrasive grains are analysed. The Sobel operator is adopted to make the edge detections. A sensitivity threshold based on the global condition is used to lower the noise. Image dilation and erosion processes are used to ensure that the edge of each loaded chip is covered by a continuous section. The ratios of chips are calculated and displayed to monitor the wheel surface working status.     

Image processing of grinding wheel surface

Identifying the situation of grinding wheel wear and loading is a very important issue for high efficiency grinding operations. This paper presents a new method that detects and identifies the chip loading and cutting edge wear of a grinding wheel using the image processing toolbox of MATLAB. The different optical characters of the metal chips and the abrasive grains are analysed. The Sobel operator is adopted to make edge detection. A sensitivity threshold based on the global condition is used to decrease the noise. Image dilation and erosion processes are used to ensure the edge of each loaded chip is covered by a continuous section. The ratios of chips are calculated and displayed to monitor the wheel surface working status.     

金刚石砂轮表面形貌测量系统

为了实现对金刚石砂轮表面形貌的非接触精密测量,开发了基于干涉原理的金刚石砂轮表面形貌专用测量系统,研究了该系统的测量原理和关键技术。根据垂直扫描白光干涉显微测量原理以及被测对象的特征,提出了适用于砂轮测量的方法,研究了系统的自动扫描范围、垂直方向的扫描方法、单次测量三维表面的恢复算法和磨粒的识别算法。结合自行设计的夹具搭建了砂轮测量系统,并对多次测量拼接算法进行了实验分析。实验结果表明:基于区域重合大小(重合度为30%~50%)的拼接算法获得的拼接前后重合区域的相关系数均大于0.8,拼接后重合区域的高度差均小于0.4μm。得到的结果显示所搭建的系统可以恢复砂轮的形貌,其测量范围和精度满足砂轮磨粒评定和分析的要求。     

圆锥滚子外径表面磨削时导轮制导面的改进

采用无心磨削方式加工圆锥滚子时,导轮制导面形状呈锥形,会与滚子外圆产生干涉,深入探讨了产生此现象的原因,提出了解决方法,给出了计算公式。     

Form-truing error compensation of diamond grinding wheel in CNC envelope grinding of free-form surface

In computer numerical control (CNC) grinding of free-form surface, an ideal arc profile of trued diamond grinding wheel is generally employed to plan 3D tool paths, whereas its form-truing errors greatly influence the ground form accuracy. A form-truing error compensation approach is proposed by using an approached wheel arc profile to replace the previously designed ideal one. The objective is to directly compensate the trued wheel arc-profile errors. It may avoid the time consumption of traditional approach that compensates the measured coordinate point errors of workpiece to an iterative grinding operation. First, the 3D tool path surface was constructed to plan the 3D tool paths. Second, the CNC arc truing of grinding wheel was conducted to analyze the form-truing error distribution relative to the applied wheel arc profile. Then, the form-truing error compensation was carried out in CNC envelope grinding. Finally, the iterative closest point (ICP) algorithm was used to match the measured coordinate points of workpiece to ideal free-form surface. It is shown that the 3D tool path surface constructed is practicable to plan arbitrary 3D tool paths for the form-truing error compensation. The ICP matching may be used to investigate 3D ground form error distribution. It is confirmed that the form-truing error compensation can directly improve the 3D ground form accuracy. It may decrease the 3D ground form error by about 20% when the 2D form-truing error is reduced by about 58% using the same truing conditions for CNC grinding.     

Application of self-inhaling internal cooling wheel in vertical surface grinding

There is less research on vertical sculptured grinding technology. Especially in high vertical surface grinding process with the cup abrasive wheel, the thermal damage is prone to happen and undermine the grinding surface integrity. This problem limits to improve the grinding efficiency and the grinding ratio greatly. Through the analysis of vertical surface grinding process and features in depth, this paper revealed the inherent mechanism of higher grinding temperature in the process of vertical sculptured grinding using the cup wheel. Based on the previous research achievements, the grinding experiments on TC4 （Ti-6A1-4V） and GH4169 are carried out utilizing the self-inhaling internal cooling wheel. The experimental results show that the self-inhaling internal cooling wheel can efficiently reduce the grinding surface temperature. Moreover, the inherent mechanism of reducing the grinding temperature using the internal cooling method is revealed. Meanwhile, under the same grinding conditions, the grinding ratio during the experiments on GH4169 using self-inhaling internal cooling method is about 3 times as high as using conventional external cooling method. And the grinding forces can be reduced by about 20%. This research revealed the inherent mechanism of higher grinding temperature in the process of vertical sculptured grinding using the cup wheel, which provides theoretical basis for the design and application of self-inhaling internal cooling wheel. At the same time, an efficient and non-invasive surface grinding method of TC4 and GH4169 is presented.     

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.     

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.     

Design and validation of a grinding wheel optical scanner system to repeatedly measure and characterize wheel surface topography

This paper describes the design and validation of an upgraded grinding wheel scanner system that controls the position of a Nanovea CHR-150 Axial Chromatism sensor along the x- and y-directions of the wheel surface to measure and characterize wheel surface topography. The scanner features a novel homing system that enables the wheel to be removed from the scanner, used on a grinding machine and then re-mounted and re-homed so that the same location on the wheel surface can be repeatedly measured and monitored. The average standard deviation for homing was 27.6 μm and 19.3 μm in the x- and y-directions, respectively, which is more than adequate for typical area scans of 25 mm². After homing, the scanner was able to repeatedly measure features that were similar in size to an abrasive grain (∼200 μm diameter) with an average error of 9.3 μm and 5.9 μm in the x- and y-directions, respectively. The resulting topography measurements were compared with Scanning Electron Microscope images to demonstrate the accuracy of the scanner. A custom particle filter was developed to process the resulting data and a novel analysis technique involving the rate of change of measured area was proposed as a method for establishing the reference wheel surface from which desired wheel topography results can be reported such as the number of cutting edges, cutting edge width and cutting edge area as a function of radial depth.     

Recognition of diamond grains on surface of fine diamond grinding wheel

The accurate evaluation of grinding wheel surface topography, which is necessary for the investigation of the grinding principle, optimism, modeling, and simulation of a grinding process, significantly depends on the accurate recognition of abrasive grains from the measured wheel surface. A detailed analysis of the grain size distribution characteristics and grain profile wavelength of the fine diamond grinding wheel used for ultra-precision grinding is presented. The requirements of the spatial sampling interval and sampling area for instruments to measure the surface topography of a diamond grinding wheel are discussed. To recognize diamond grains, digital filtering is used to eliminate the high frequency disturbance from the measured 3D digital surface of the grinding wheel, the geometric features of diamond grains are then extracted from the filtered 3D digital surface, and a method based on the grain profile frequency characteristics, diamond grain curvature, and distance between two adjacent diamond grains is proposed. A 3D surface profiler based on scanning white light interferometry is used to measure the 3D surface topography of a #3000 mesh resin bonded diamond grinding wheel, and the diamond grains are then recognized from the 3D digital surface. The experimental result shows that the proposed method is reasonable and effective. __________ Translated from Journal of Dalian University of Technology, 2007, 47(3): 358–362 [译自: 大连理工大学学报]     

Recognition of diamond grains on surface of fine diamond grinding wheel

The accurate evaluation of grinding wheel surface topography, which is necessary for the investigation of the grinding principle, optimism, modeling, and simulation of a grinding process, significantly depends on the accurate recognition of abrasive grains from the measured wheel surface. A detailed analysis of the grain size distribution characteristics and grain profile wavelength of the fine diamond grinding wheel used for ultra-precision grinding is presented. The requirements of the spatial sampling interval and sampling area for instruments to measure the surface topography of a diamond grinding wheel are discussed. To recognize diamond grains, digital filtering is used to eliminate the high frequency disturbance from the measured 3D digital surface of the grinding wheel, the geometric features of diamond grains are then extracted from the filtered 3D digital surface, and a method based on the grain profile frequency characteristics, diamond grain curvature, and distance between two adjacent diamond grains is proposed. A 3D surface profiler based on scanning white light interferometry is used to measure the 3D surface topography of a #3000 mesh resin bonded diamond grinding wheel, and the diamond grains are then recognized from the 3D digital surface. The experimental result shows that the proposed method is reasonable and effective.     

Identification of a model of grinding wheel life by the group method of data handling

A mathematical model for grinding wheel redress life is identified by the polynomial theory of complex systems. Wheel speed, feed, grain size and grade are chosen as the independent variables from among the factors considered to have an effect on wheel wear through the identification of the model. The model obtained enables the redress life to be predicted for all combinations of grinding wheel, work material and grinding conditions, and serves as an aid in the optimization of the grinding process.     

An active manufacturing method of surface micro structure based on ordered grinding wheel and ultrasonic-assisted grinding

At present, many studies have shown that crosshatch micro structures can effectively improve surface performance. This paper presents a method for manufacturing micro structure based on ultrasonic-assisted grinding (UAG) and ordered grinding wheel. Firstly, the parameters of ordered grinding wheel and the surface characteristic parameters in relation to working performance are proposed. According to the kinematics of grinding, the governing equation between the surface characteristic parameters and the machining parameters is established. Based on the proposed characteristic parameters, the pattern parameters and machining parameters are inversely solved by the governing equation. The crosshatch micro structure manufacturing based on ordered grinding wheel and ultrasonic-assisted grinding is achieved, and because the fabrication technology of the grinding wheel is not mature, its correctness and feasibility are preliminary verified by the numerical simulation method and grinding experiment. The paper method is original for the active manufacturing of the crosshatch micro structure and is of reference value for the micro structure active manufacturing.     

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...     

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.