Modelling and simulation of surface topography in ultra-precision diamond turning

Dynamic vibrations of air bearing motor spindles have significant influence on the surface quality in ultra-precision machining. In this article, the influence of the vibration caused by the unbalanced magnetic force on the diamond turning is investigated on the basis of the theoretical and experimental method. A permanent magnet motor model (10 poles and 12 slots) is built and then simulated to gain a periodic unbalanced magnetic force. The effects of unbalanced magnetic force on the inclination of the spindle shaft is analyzed, which would affect the surface quality of the workpiece, and the surface topography of the workpiece is predicted during an unbalanced magnetic force acting on air bearing motor spindle. The theoretical analysis and experimental turning results validate that the angle between the direction of unbalanced magnetic force and the feed direction has a certain relationship with the profile of the machined surface. Also, under different turning speeds and directions, the surface topography of the machined workpiece shows a 10-cycle-per-revolution pattern, which has good agreement with the simulations of periodic unbalanced magnetic force. This research work provides a theoretical foundation for the fault diagnosis of air bearing motor spindle caused by motor rotor eccentricity and its effect on surface generation in turning.

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Diffractive optical characteristics of nanometric surface topography generated by diamond turning

Journal of Manufacturing Processes ◽

10.1016/j.jmapro.2021.04.012 ◽

2021 ◽

Vol 67 ◽

pp. 23-34

Author(s):

Dongxu Wu ◽

Chengwei Kang ◽

Fusheng Liang ◽

Guangpeng Yan ◽

Fengzhou Fang

Keyword(s):

Surface Topography ◽

Diamond Turning ◽

Optical Characteristics

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Development of a Non-Contact Tool Setting System for Precision Diamond Turning

Materials Science Forum ◽

10.4028/www.scientific.net/msf.505-507.367 ◽

2006 ◽

Vol 505-507 ◽

pp. 367-372 ◽

Cited By ~ 3

Author(s):

Choung Lii Chao ◽

T.A. Cheng ◽

D.C. Lou ◽

Chung Woei Chao

Keyword(s):

Contact Point ◽

Diamond Turning ◽

Optical Diffraction ◽

Sampling Step ◽

Error Band ◽

Sampling Distance ◽

Tool Shape ◽

Tool Setting ◽

Ultra Precision ◽

Cnc Controller

Precise and efficient tool setting technique and accurate tool shape monitoring are of essential importance in ultra-precision diamond turning operation. The traditional way of tool setting are typically laborious, inefficient and rely heavily on experience. A big part of the tool setting is done by using a contact probe such as LVDT. The contact tool setting station can normally, depending on the resolution of the probes, place the tool tip to within a 1~10μm positioning accuracy. However, it is running the risk of damage the delicate tool tip and has the ambiguity introduced by contact point of tool and touch probe. The optical/non-contact way of setting the tool do have the advantage of not having to touch the tool, but its resolution is limited by the optical diffraction limit and the resolution of the CCD device used (mm/pixel). A non-contact precision tool setting system is developed and built in this study using edge-detection image processing and sub-pixel dividing techniques in conjunction with CNC controller of the precision turning machine to improve the system presently available. Depending on the sampling distance of the images, the error band gets wider when the sampling step becomes larger. In the case of 0.1μm sampling distance the obtained error band was within ±0.1μm and the results showed that tools of different shapes namely round, half-round and sharp tool could all be positioned to within an error band of ±0.1μm by using the developed tool setting system.

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Characteristics of the Wheel Surface Topography in Ultra-precision Grinding of Silicon Wafers

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.389-390.36 ◽

2008 ◽

Vol 389-390 ◽

pp. 36-41

Author(s):

Feng Wei Huo ◽

Dong Ming Guo ◽

Ren Ke Kang ◽

Zhu Ji Jin

Keyword(s):

Surface Topography ◽

Sampling Interval ◽

Grinding Wheel ◽

Height Distribution ◽

Wheel Surface ◽

Diamond Grinding Wheel ◽

Diamond Grinding ◽

Cutting Surface ◽

Ultra Precision ◽

Cutting Direction

A 3D profiler based on scanning white light interferometry with a lateral sampling interval of 0.11μm was introduced to measure the surface topography of a #3000 diamond grinding wheel, and a large sampling area could be achieved by its stitching capability without compromising its lateral or vertical resolution. The protrusion height distribution of diamond grains and the static effective grain density of the grinding wheel were derived, and the wheel chatter and the deformation of the wheel were analyzed as well. The study shows that the grain protrusion height obeys an approximate normal distribution, the static effective grain density is much lower than the theoretical density, and only a small number of diamond grains are effective in the grinding process with fine diamond grinding wheel. There exists waviness on the grinding wheel surface parallel with the wheel cutting direction. The cutting surface of the grinding wheel is not flat but umbilicate, which indicates that the elastic deformation at the wheel edges is much larger than in the center region.

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Measurement and Compensation of Tool Contour Error Using White Light Interferometry for Ultra-Precision Diamond Turning of Freeform Surfaces

International Journal of Automation Technology ◽

10.20965/ijat.2020.p0654 ◽

2020 ◽

Vol 14 (4) ◽

pp. 654-664 ◽

Cited By ~ 1

Author(s):

Kodai Nagayama ◽

◽

Jiwang Yan

Keyword(s):

White Light ◽

High Efficiency ◽

Diamond Tool ◽

Microlens Array ◽

Diamond Turning ◽

Contour Error ◽

Form Accuracy ◽

Freeform Optics ◽

Ultra Precision ◽

Quick Measurement

In ultra-precision diamond turning of freeform optics, it is necessary to obtain submicron-level form accuracy with high efficiency. In this study, we proposed a new method for the quick measurement and compensation of tool contour errors to improve the form accuracy of the workpiece. In this method, the nanometer-scale contour error of a diamond tool is quickly and precisely measured using a white light interferometer and then compensated for, before machining. Results showed that the contour of a diamond tool was measured with an error less than 0.05 μm peak-to-valley (P-V) and the feasibility of error compensation was verified through cutting experiments to create a paraboloid mirror and a microlens array. The form error decreased to 0.2 μm P-V regardless of the contour error of the diamond tools when cutting the paraboloid mirror, and that of the microlens array was reduced to 0.15 μm P-V during a single machining step.

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