Papers by Keyword: Curve Grinding

Abstract: The grind test is detected curve of the grinding surface roughness of thin in use of three-dimensional contour in this paper, major influence factor in the accuracy of surface roughness is proposed in the analysis based on grinding surface roughness.Trend of the grinding surface roughness is simulated in Matlab. It is expected that best surface roughness can be obtained by selecting the appropriate cutting speed and feed rate for the material pair of workpiece and cutting tool.

Abstract: The curve NC grinding methods in presnet are analyzed. On the basis of this, a new curve NC grinding method―region contact grinding (RCG) method is proposed. With this method, the contact point between grinding wheel and workpiece can be controlled in the given contact zone. The problom of grinding wheel's distortion which is produced by contact point excessively deviating from symmetrical central plane of grinding wheel can be overcome. In order to the grinding mode, a new interpolation algorithm―region equiangular linear interpolation (RELI) is proposed. Namely, in terms of the convex-concave property of processing curve, some grinding regions are divided. In each grinding region, the grinding wheel's swing angle within each interpolation cycle is evenly distributed. Thereby, in the process of grinding a convex-concave curve, grinding wheel's contact points totally locate in the range of contact zone angle.

Abstract: This paper deals with an on-line mismachining error measurement for curve grinding based on digital image processing. Using CCD camera, the contour of the workpiece’s finished surface is captured and the image is preprocessed for denoising and edge detecting. The worktable is guided by the image of the finished workpiece to follow the path of the finished contour and then the real curve of the finished workpiece is measured by fitting a curve according to the moving path of the worktable. Finally, the machining error is obtained by comparing the measured curve with the theoretical curve of the workpiece. This method is applied to a CNC curve grinding machine MD9040. A measurement experiment is given. The experiment results show that the measurement method offers high detection precision and can be used in wide fields, especially for measuring the parts with complex curve.

Abstract: Image analysis was used to evaluate the curve grinding process. The measurement system organization and its principle of operation were introduced. Some key technologies that influence the system precision were also studied in details. Real-time image of work piece and wheel grinding can be gathered while using CCD camera. For image de-noising, a kind of wavelet threshold function was presented to calculate the new wavelet coefficients. Local threshold algorithm was used to compute different scale threshold, another threshold is suggested when MSE is minimum. Image signals are reconstructed through invert discrete wavelet transformation with the new wavelet coefficients. For the purpose of increasing the measurement precision, a closed mathematical model of sub-pixel edge detection operator was founded according to the gray moment operator’s invariant characteristics and Tabatabai’s first three sample gray moments. An application of system validity and the comparison results of work piece were also given. From experiments it can be said that the proposed method in this paper is effective, and its detection precision and results are reasonable.

Abstract: In traditional NC curve grinding, the grinding wheel’s rotary surface is generally not on the grinding point’s normal direction, which will bring the distortion of grinding wheel and decrease the machining precision. This paper presents a new technology, which is called the non-interference normal tracking for NC curve grinding process. By controlling the worktable to rotate in the x-y plane, the superposition between the rotary surface of the grinding wheel and the normal vector of the workpiece’s contour is realized, and the interference between the wheel’s body and the workpiece could be avoided at the same time. A mathematic model is established and an algorithm to calculate the worktable’s rotary angle is proposed. Finally, the algorithm is applied in a new-type digital curve grinder successfully. The results show that the method is reliable and effective.

Abstract: This paper presents a new technology, which is the normal tracing, for NC point-grinding of the curve. The development of the technology is based on the simultaneous three-axis machining. By controlling the superposition between the rotary surface of the grinding wheel and the normal vector of the curve, point contact between them is realized. So grinding just like turning, the abrasive machining of the complex curve is easy to be realized. The main advantage of the technology is the fact that it can not only reduce the deformation of the grinding wheel and simplify the NC programming, but also improve surface quality and profile accuracy. This paper builds the mathematic model of the normal tracing by analyzing the geometric property and the kinematic relationship between the wheel and the work piece. Then the control algorithm of the normal tracing is given and used in a new-type digital curve grinder successfully, MD9040 developed by ourselves.

Abstract: An on-line image measurement system for curve grinding was schemed out according to the working process. Because of interaction between detection precision and field of view, it is difficult to realize high detection precision at a large field of view. In order to settle this problem, a detection method based on circular tolerance zone was presented according to grinding process and wheel shape. Real-time images of work piece can be gathered while using synchronal control and outer trigger technology. Using curve fitting method, the work piece image edge can be located to sub-pixel values. Experiments show that the proposed method in this paper is effective, and its detection precision and results are reasonable.

Abstract: A CCD on-line image measurement system for curve grinding was schemed out according to the working process. Real-time images of work piece and wheel grinding can be gathered while using synchronal control and outer trigger technology. For the purpose of increasing the measurement precision, we presented a new method for locating edges in digital images to sub-pixel values based on local interpolation and spline fitting. An application of its validity and the comparison results of grinding wheel wear are also given. Experiments show that the proposed method in this paper is effective, and its detection precision and results are reasonable.