Papers by Author: Xiang Yang Lei

Abstract: Grinding is a processing method that involves duplicating shape accuracy, so the shape accuracy of the grinding wheel plays a crucial role in machining accuracy. However, this accuracy is difficult to obtain. This paper describes an on-machine wheel profile measuring method that uses a non-contact displacement sensor to obtain the shape accuracy of an arc grinding wheel in a 3-axis aspheric surface grinding machine. This method involves data processing with object radius confined filtering, as well as evaluation using the methods of fitting residual error, measurement uncertainty, and machining result simulation. To verify the feasibility of this measuring method, experiments were performed using two diamond grinding wheels (FEPA D91 with grit size 75-90 μm, and FEPA D15 with grit size 10-25 μm). The experimental results indicate that the method is accurate enough to give the arc grinding wheel profile measurement, while the measuring uncertainty is of the same order of magnitude as the grit size (that is, tens of μm). Moreover, the simulation of the grinding effect with wheel profile measurement data can derive the relationship between the wheel profile error and the machining form error, and can be used to instruct the truing time determination for precision grinding.

Abstract: According to needs of aspheric lens grinding and measurement with X/Y/Z 3-axis grinding machines, a CAM system is designed and implemented. The system, based on the parallel grinding geometry model, has realized the function of grinding locus planning, form error compensation, NC program auto-generation, on-machine measurement, grinding wheel on-machine measurement, simulation and technical database. To verify the stability of this CAM system, experiments were performed with three independent machining experiments. The experimental results indicate that the system realized the whole process of aspheric grinding, and it improved the machining efficiency and automation. Especially, this system adopted on-machine form error compensation technology and improved the machining accuracy. By implementing the error compensation integrated in the CAM system, the surface form error of a 430mm×430mm aspheric lens is decreased from PV8.2µm to PV4.1µm. The grinding accuracy was improved 100%.

Abstract: In this paper, an on-machine profile measuring system for aspheric ground surface was presented, which involved data processing with improved two-dimensional weighted mean filtering and free form surface fitting. To verify the reliability of this system, a calibration experiment was done by comparing the measuring results of Ф320mm mirror between the WYKO 24 inch interferometer and the on-machine measuring system. The experiment results show that the on-machine measurement is effective and it can provide foundation for compensation machining. By comparing the measurement experiment results of the Keyence LC2430 with the WYKO interferometer, it is demonstrated that the deviation of PV is better than 0.23μm and the deviation of RMS better than 0.08μm.

Abstract: The causes of machining errors are very complicated and apt to mutual influence in aspheric grinding, so it is difficult to improve machining accuracy by control one cause. To compensate the machining error of large aspheric grinding, an error-compensation technique using on-machine profile measurement system in three axes grinding machine are presented. To verify the effectiveness of the compensation machining and the reliability of the measurement system, experiments on high-precision grinding machine were performed. Moreover, the compensation machining with the on-machine measurement substantially decreases the machining errors and improve machining accuracy by more than 45%, compared with the non-compensation machining.

Abstract: Ultra precision grinding is currently the main technology for large scale advanced optical lens machining. In this paper, the machining system of ultra precision surface grinder is investigated. The experiments of new wedged aspheric lens with the dimension of 430*430mm have been conducted by SD600 diamond wheel, and the parallel grinding, cup truing and on-machine measuring are used for good accuracy. The results show the effective machining system and the problem for next research.