Progress of Precision Engineering and Nano Technology

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Authors: Ming Zhou, X.D. Liu, S.N. Huang
Abstract: Soda-lime glass is a typical brittle material, which is difficult to realize ductile-regime machining by using conventional cutting technology due to the extremely small critical depth of cut. In this work, the micro-deformation characteristics of this kind of materials were analyzed by micro indentation. Ultrasonic vibration assisted diamond cutting was performed in order to investigate the effect of tool vibration on material removal process and surface quality. The profiles of cut surfaces were measured and compared with those obtained by conventional diamond cutting. Real depths of cut in ultrasonic vibration cutting correspond well with the nominal ones. The change in the tribology of the cutting process as well as the alteration of the deformation mechanism of the work material might be responsible for the reduction in tool wear in vibration cutting.
Authors: M.N. Cheng, Chi Fai Cheung, Wing Bun Lee, Sandy To
Abstract: Ultra-precision raster milling is an emerging manufacturing technology for the fabrication of high precision and high quality components with a surface roughness of less than 10 nm and a form error of less than 0.2 μm without the need for any subsequent post polishing. Surface quality of a raster milled surface is affected by process factors and material factors, respectively. The process factors involve cutting conditions, cutting strategies, and relative vibration between the tool and the workpiece which are related to the cutting geometry and the dynamic characteristics of the cutting process. The material factors considered are material property and swelling of the work materials. Due to different cutting mechanics, the process factors affecting the surface quality are more complicated, as compared with ultra-precision diamond turning, such as swing distance and step distance. This paper presents an experimental investigation of the distinctive process factors affecting the surface roughness in ultra-precision multi-axis raster milling. Experimental results indicate that the influence due to the process factors can be minimized through a proper selection of operational settings and better control of dynamic characteristics of the machine.
Authors: Chi Fai Cheung, Wing Bun Lee, Sandy To, H.F. Li, Su Juan Wang
Abstract: The fabrication of high-quality optical microstructural surfaces is based on fast tool servo (FTS) machining. It makes use of auxiliary piezo-electric driven servos to rapidly actuate the diamond tool with a fine resolution and a sufficiently high bandwidth for machining optical microstructures with submicrometer form accuracy and a nanometric surface finish without the need for any subsequent post processing. However, the achievement of a superior mirror finish and form accuracy still depends largely on the experience and skills of the machine operators, acquired through an expensive trial-and-error approach to using new materials, new mircostructural surface designs, or new machine tools. As a result, this paper, a model-based simulation system is presented for the optimization of surface quality in the FTS machining of optical microstructures. Preliminary experimental work and the results are also presented.
Authors: Su Juan Wang, Chi Fai Cheung, Sandy To, Wing Bun Lee
Abstract: Recently, the high quality and high productivity in fabrication of freeform optics has been of primary interest in manufacturing industries, such as die and mould manufacturing, aerospace part manufacturing, and so forth. However, the fabrication of freeform optics is currently expensive and vastly complex. Ultra-precision raster milling can produce non-rotational symmetric surfaces with sub-micrometric form accuracy and nanometric surface finish without the need for any subsequent post polishing. While, there is little research work focus on this kind of machining method. This paper presents a framework of a tool path generation system for freeform surface ultra-precision raster milling. This system includes model of freeform optics, tool path generator, interference monitor and an optimization model of machining parameters. The tool path generation system can generate interference free and optimal tool path for machining freeform surfaces. Some simulation results have been presented to illustrate the performance of the system.
Authors: H.F. Li, Chi Fai Cheung, Ling Bao Kong, Wing Bun Lee, Sandy To
Abstract: Ultra-precision freeform surfaces have become widely used in advanced optics manufacture. Although these surfaces can be fabricated by ultra-precision freeform machining technology with sub-micrometer form accuracy and surface finish in nanometer range, our current understanding on the evaluation of surface quality of these surfaces is still far from perfect. In this paper, a study of measurement technology for ultra-precision freeform surfaces is presented.
Authors: Ling Bao Kong, Chi Fai Cheung, Wing Bun Lee, Sandy To
Abstract: This paper presents an integrated platform for modelling and measurement of freeform surface generation in ultra-precision raster milling. It is composed of several components which are optics design component, tool path generator, modelling system, measurement system, evaluation component, compensation component and optimization component, respectively. The research emphasizes on modelling and simulation of freeform surface generation, the prediction of the cutting performance and hence the optimization of cutting strategy in the ultra-precision raster milling of freeform surfaces. A measurement system is also proposed to carry out a fast and efficient measurement plan of freeform surfaces. Non-uniform Rational B-Spline (NURBS) will be employed for the development of the integrated platform which will meet Standard for the Exchange of Product model data (STEP).
Authors: Y. Gao, H. Lai
Abstract: An active cooling approach for coolant during ductile material grinding is proposed and examined. The aim is to enhance surface quality and to enhance productivity. The problem associated with the cryogenic cooling approach and the one with the chilled air approach are addressed. An active cooling prototype was developed utilizing a compact heat pump design, which is easy to use, movable, and can be easily fitted into different type of machine designs with relatively low costs. The system is based on the use of forced convection of the heat generated during the machining process. Experimental and computational studies of the effects of actively cooled coolant for grinding ductile materials are carried out. The experimental results show that the use of actively cooled coolant is able to improve surface quality by up to 29.95% on average in terms of surface roughness Ra. Computational testing results show that the heat can be taken away more effectively by using the proposed approach. The results of optical and SEM examinations also confirmed that the proposed approach is advantageous.
Authors: S. Tse, Y. Gao
Abstract: For nano-positioning systems with piezoelectric actuators used for dynamic grinding control, sinusoidal command signals will used and will give additional problems compared with the commonly used step signals because of the hysteresis effects, which require a good modeling approach. The proposed approach of multiple polynomial regression with first order continuity gives a relative modeling error of 2.65%. The method reduces the error by 26.3-80.2% in comparison with the methods using the single, dual, and multiple polynomial regression with zero order continuity.
Authors: Ying Xue Yao, Shun Zhou Yu
Abstract: PC-based software computer numerical control (CNC) system is the ideal for open CNC system, but there are some problems about the current open CNC system, such as the limitation of interpolation cycle, demanding on high-speed and high precision machining and the limitation of operation system (OS). So advances a novel PC-based architecture for compiled-type software CNC system, in the architecture, the general Windows is adopted as CNC platform and adopts two huge memories acting as data buffer to solve real time problem. And then analyzes the structure and basic principle of compiling system. The hardware has been developed based on this architecture and applied in the CNC system.
Authors: Jian Guang Li, Wing Bun Lee, Chi Fai Cheung, Sandy To, J.J. Du, Z.Q. Yin
Abstract: Virtual manufacturing (VM), which primarily aimed at reducing the lead times to market and costs associated with new product development, offers various test-beds for the time-consuming and expensive physical experimentation. Since surface roughness and form accuracy play essential roles in the functional performance of the products machined with ultra-precision machining technology. An optimizer, VSPDT (virtual single point diamond turning) system was developed for the purpose of form error compensation and optimal cutting parameters selection. In this paper, the keys issues for developing VSPDT using virtual manufacturing technology were highlighted such as framework of system, virtual workpiece, virtual machining and inspection, etc. At the end of the paper, A VSPDT was developed and applied to predict and compensate the form error, select optimal cutting parameters by using a 2-axis CNC ultra-precision turning machine.

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