Arc error separation and compensation technology of rectangular aspheric surface

To study the effect of the wheel-arc error on large-scale rectangular axisymmetric aspheric machining, the grating parallel grinding method is adopted and the mathematical model of wheel-arc error separation is built. The factors that affect the surface accuracy are analyzed and it is found that the wheel-arc error is the most sensitive in the factors. According to the grinding and measurement method, the wheel-arc error is separated. Using the new wheel-arc radius modified by separated wheel-arc error and the new compensation data subtracted from wheel-arc error, the separating error compensation grinding is carried out and proves effective. The experimental results show that the aspheric surface error decreases by 14% and 35% after separating error compensation grinding in rough and fine grinding conditions. The error model can separate the wheel-arc error effectively and the accuracy of the aspheric surface is improved

The Technique of Online Measurement and Data Processing for Aspheric Machining

Conference Name:International Conference on Manufacturing Science and Engineering (ICMSE 2009). Conference Address: Zhuhai, PEOPLES R CHINA. Time:DEC 26-28, 2009.In the traditional precision machining, it is easy to introduce positioning error because of the separation of the machining and the measurement. In order to solve this problem, an online measurement technique for aspheric grinding has been put forward. It measured the workpiece with sensor which was fixed to the high-precision machine tool. It processed data with the algorithm of Two-dimensional weighted average filtering and curve fitting based on Gauss-Newton and Levenberg-Marquardt least-square method. The experimental results indicated that the fitting residual error was less than 3 x 10(-6) mm. In the grinding process, the measurement error was of the order of the magnitude of 10(-3) mm. It can be concluded that the technique measures the surface exactly, and improves the machining accuracy effectively by providing accurate data for compensation

Dynamic removal function modeling of bonnet tool polishing on optics elements

The dwell time function of the bonnet tool polishing on optics elements is achieved based on static removal function in recent studies. But the polishing tool keeps moving during the process, it's necessary to do the research on dynamic removal function. The static and dynamic contact zone is acquired through finite element simulation analysis, and so is the contact pressure. Both of the contact zones are circle and the size of them are almost the same. The peak point of the dynamic contact pressure has an offset contrary to the direction of the tool movement compared to the static contact pressure. The dynamic contact pressure distribution function is deduced by using the least square method based on the theory that the static pressure distribution function is a modified Gaussian function. The device which can extract both the dynamic and static contact zone is set up to capture them on the condition of different offset. Then the simulation results are verified. The dynamic removal function is deduced and numerical simulated based on the forward simulation and experiment results. The removal rate of the dynamic removal function is smaller than the static removal function and its nadir has a deflection compared to the latter. ? 2013 Journal of Mechanical Engineering

Precision model and analysis of large axisymmetric aspheric grinding

The general error model of high precision surface grinder is presented by using rigid body kinematics theory and coordinate transformation. To meet the machining requirement of large axisymmetry aspheric lens, the grating parallel grinding method is adopted. Considering high precision surface grinder structure and the main error factors affect the machining accuracy of large aspheric, a large axisymmetric aspheric error model is proposed, which can be used to predict surface accuracy and compensation grinding. The main error factors are discussed and it is shown that the straightness error, positioning error and arc radii error are main errors that effect surface error distribution, meanwhile, surface error value is the mixed result of each individual error. The experiments are carried out and in agreement with the theoretical results. The grinding experiment shows that the model can well predict surface accuracy and surface accuracy is improved after compensation grinding. ? 2013 Journal of Mechanical Engineering

Control techniques of bonnet polishing for free-form optical lenses with precession

Control techniques of bonnet polishing free-form optical lenses with 'precession' is studied, according to the processing characters of free-form optical lenses, to figure out the rotating angles of two virtual axes of bonnet tool, which lead to the controllability of spin axis of bonnet tool. The spin axis of bonnet tool is taken as the object, due to the difference of the local normal of each polishing point and the angle between the spin axis of bonnet tool and local normal is keeping constant in polishing process, a method about how to set up basic coordinate and corresponding coordinate of polishing point is proposed, aiming to get the positions of spin axis of bonnet tool in polishing process, by which a movement model can be obtained by combining with rotating coordinate transformation; Then control algorithm is added to the movement model, and rotating angles of two virtual axes of bonnet tool when polishing each point on free-form optical lenses are calculated. At the end, simulations in polishing different directions of free-form optical lens in Matlab are carried out, to get the curves of precession control and the simulated precession angles, the results reveal that the movement model and control algorithm presented are both correct. ? 2013 Journal of Mechanical Engineering

Carbon Peak and Carbon Neutrality Path for China’s Power Industry

The low-carbon transformation of power sector is significant for achieving the goal of carbon peak and carbon neutrality in China. Based on the evaluation of power carbon budget, three power transformation scenarios of deep low-carbon, zero carbon, and negative carbon were built, the key boundary conditions such as power consumption demand were studied, and a path planning optimization model was established in the paper. Using the GESP-V software package for optimized analysis, the low-carbon transformation paths were determined for power structure, power carbon emissions, and power supply costs under different scenarios. The major issues that are critical for the low-carbon transformation of the power system were discussed, including coal power development, renewable energy development and utilization, diversified supply of clean energy, and electric power balance. Several suggestions were further proposed. Specifically, the top-level design should be strengthened to steadily plan the transformation pace, major low-carbon technologies should be developed to coordinate the overall technology and industrial layout, and the market mechanism with balanced interests should be improved while establishing a green finance policy system. The high-quality low-carbon transformation of China’s power sector in the medium and long term can be promoted through the coordination of policies, technologies, and mechanisms

Research on Virtual NC Technique in High Precision Grinding Process

Conference Name:International Conference on Measuring Technology and Mechatronics Automation. Conference Address: Zhangjiajie, PEOPLES R CHINA. Time:APR 11-12, 2009.A virtual machining system based on virtual manufacturing technique and NC machining technique for high precision grinding machine is developed in this paper, which can realize all processes from the establishment of NC procedure to grinding machining simulation. The virtual machining environment is built with OpenGL technique on the platform of Visual C++, and the geometric simulation and impact interference checking are realized by C++ language. The structure of machining simulation system and its function are proposed. According to grinding machine tool characteristic, appropriate machining path planning is designed. The research shows that the simulations are reliable to complete the virtual grinding machining of the product by checking machining ability, rationality of design, prediction manufacture circle, and promptly modifying design. The method provides the theoretical foundation and reference value of practical application for structure design of grinding machine