Papers by Author: Zhen Zhong Wang

Abstract: A multi-segments stitching method is proposed to obtain two-dimensional profile of large scale aspheric components during grinding process. We firstly analyze the corresponding relation between surface features of aspherics and measurement range of profilometer. According to multi-body system theory and slope difference, a mathematical model of multi-segments stitching method is constructed. Further, the multi-segments stitching errors based on 400 mm aspheric profile are simulated with different translation amounts, rotation angles, translation errors as well as rotation errors. The simulation results indicate that the translation error is the key factor for measuring accuracy of the multi-segments stitching method. In addition, the standard deviations of multi-segments stitching errors are between 0.2 μm and 0.4 μm as the four factors are set to the proper values. To verify the simulation analysis results, an experimental setup, including Talysurf PGI 1240 and fixture, is applied to detect a 150 mm profile line on the aspheric surface. The experiment results show that the standard deviations of multi-segments stitching errors are almost within 1 μm when the rotation angle is under 7° and the translation amount is under 11 mm. The multi-segments stitching method can employ a small-range profilometer to achieve measurement of large scale aspheric surfaces with submicrometer accuracy.

Abstract: Due to the range of the measuring system is limited in the measurement of large aspheric optical elements, test is hard to be once fulfilled, so coordinate measurement based on multi-section stitching is proposed, and the least square mathematical model of large aperture optical elements multi-section stitching is built. Moreover, the profiler Talysurf PGI 1240 made by Taylor Hobson company is used for study. The result shows that, the method is suitable for multi-section data stitching for large aspheric optical elements, and possesses many advantages, such as fast speed, high accuracy and strong operability, etc.

Abstract: This paper focus on the relationship between PA and the distribution of polishing pressure, on the basis of the theory that the distribution of polishing pressure is a Modified Gaussian Function and has highly symmetry. Through the simulation experiments, the optimum PA has been determined. And it’s further validated that this optimum PA fits for polishing large aspheric mirror under the conditions with both different internal pressure and bonnet decrement by a series of simulation experiment. It’s also found that PA makes little difference to the size of the contact area and the bonnet decrement has greater influence to the size of the contact area than the internal pressure.

Abstract: Nowadays, the demands of large scale surface devices are becoming popular in engineering fields. The grinding process is one of the common methods to achieve the high quality of large scale workpiece. But the final form accuracy of large scale devices is always low. Then it is necessary to analyze the error mechanism of grinding machine on the form accuracy of large scale workpiece. In this paper, the influencing factors of surface grinding machine with horizontal spindle and rectangular table were analyzed firstly. Then the mechanism of guiding accuracy on the surface form accuracy was discussed. It is found that the Z-axis’ guiding accuracy could seriously influence the surface form accuracy. Finally, the face grinding experiment of large scale iron workpiece (420mm×420mm) was performed and the surface form accuracy was measured. The experimental result was in agreement with the theoretical result. It can be concluded that the Z-axis guarding accuracy of grinding machine should be exactly controlled to achieve the high surface precision of large scale device.

Abstract: In this paper, according to the bonnet polishing technology, in order to get the change regularity of the bonnet’s deformation, the inflated deformation model of the bonnet, which is made all of rubber or made of rubber but with a nylon enhancement layer, is established and analyzed by using the FEA simulation. And then, by simulating the process of the bonnet polishing the plane wafer, it achieves the contact pressure curve which varies with the bonnet decrement. According to the Preston equation, k can be acquired through the experiment, v can be achieved through mathematical modeling, and p has been achieved in this paper. Thus, the removal function based on FEA will be acquired.

Abstract: As the reliable technology, ultrasonic assisted machining is widely used for brittle materials. This paper provides a two-dimensional(2D) ultrasonic vibration assisted machining technology with tool vibration using elliptical vibrator with longitudinal mode and bending mode, and set up the experiment device. Si wafer is taken as the workpiece, and single point cutting experiments for micro groove are investigated. For the further application, the ultrasonic assisted polishing experiment with wheel block is executed. Experimental results indicate that ultrasonic assisted cutting with tool vibration can improve the cutting performance and enhance the ductile removal. And the ultrasonic assisted polishing with whetstone piece makes the better surface roughness and higher material removal rate.

Abstract: Large scale wedge/aspheric lens element is a combination of wedge prism and aspheric lens as a single piece component forming a decentred lens, which is primarily manufactured by Computerized Numerical Control (CNC) machining, especially 3-axis CNC grinding. This paper presents an efficient tool path generation approach based on isophote interpolation. The interpolation guarantees that interpolated points always stay on the iso-inclination curve of the parametric surface. This symmetry ensures that the method can improve and automate large scale wedge/aspheric lens element machining for 3-axis CAD/CAM systems. As part of the validation process, the tool paths generated are analyzed and compare with the desired part.

Abstract: As a new fixed-abrasive machining method, chemo-mechanical grinding (CMG) is developed from chemical mechanical polishing (CMP), with the obvious advantage of geometric accuracy determinacy and no slurry. To improve material removal rate and enhance the popularity of CMG, this paper introduces a combined grinding method, i.e., two dimensional ultrasonic vibration assisted CMG (2D-UACMG). Si wafer is taken as the workpiece and the influence of ultrasonic vibration modes and process parameters on the surface roughness and the material removal is examined. The results show 2D-UACMG can obtain better surface quality with little surface damage at nanometer level compared with the conventional CMG without the ultrasonic vibration.

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.

Abstract: In precision measurement, the existed error of measuring system influences surface accuracy more. This paper provides an error analysis focusing on the research effort on aspheric lens on-machine measurement for form accuracy. And the error parameters including positioning error of coordinate origin, tilt angle and radius error of probe head are investigated. It was known that it was quite difficult to obtain the parameters by detecting instruments, so the method of error separation and correction based on measuring standard parts is presented in this paper to guide the inverse solution for higher measuring accuracy. Also, a measuring experiment with Φ210mm lens is executed. Experimental results indicate that the method based on standard parts is suitable for on-machine precision measuring of aspheric lens.