Papers by Author: Yun Feng Peng

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: 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: A theoretical discussion has been presented for the ductile chip formation in grinding of brittle materials. The single abrasive grit was dealt with a top-rounded cutter removing material of varying undeformed chip thickness. The force model in the chip formation zone was established. The stress analysis showed that larger compressive stress and shear stress can be generated in the chip formation zone, which shields the growth of pre-existing flaws in the material by suppressing the stress intensity factor. When the stress intensify factor is smaller than fracture toughness and the resolved shear stress exceeds the critical flow stress of the material, the ductile chip is formed. Experiments of monocrystal silicon grinding were conducted. The results show that the thrust force is much larger than the cutting force, which ensures the larger compressive stress in the chip formation zone and the formation of ductile chip.

Abstract: In this paper, the with-in-wafer non-uniformity (WIWNU) of the lager quadrate optic in the fast polishing process (FPP) is discussed from the machine side. At the machine side, the non-uniform stress on the wafer surface is the major reason for the non-uniform material removal rate which results in the WIWNU. Stresses arise mainly from two sources, namely the pressure exerted by the polishing pad and shear stress due to the relative motion between the wafer and pad. Based on the special chemical mechanical polishing FPP, the kinematic motion of the wafer is analyzed and the non-uniform stress is analyzed by a 3D axisymmetric quasi-static model. The WIWNU can be reduced by adjusting the stress.