The Experts below are selected from a list of 252 Experts worldwide ranked by ideXlab platform
Junji Watanabe - One of the best experts on this subject based on the ideXlab platform.
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Atomic-Scale Planarization of Single Crystal Diamond Substrates by Ultraviolet Rays Assisted Machining
Key Engineering Materials, 2010Co-Authors: Mutsumi Touge, Satoru Anan, Akihisa Kubota, Shogo Wada, Yoshitaka Nakanishi, Junji WatanabeAbstract:The Ultra-Precision Polishing assisted by the ultraviolet rays irradiation was performed to achieve the atomic-scale planarization of the single crystal diamond substrates. This Polishing method is a novel and simple Polishing method characterizing by a quartz disk and an ultraviolet irradiation device. The principle three crystal planes of the diamond substrate were polished by this method. The polished surfaces were evaluated by an optical interferometric profilers (Wyko), an atom force microscope (AFM) and LEED (low-energy electron diffraction). The surface roughness of the polished diamond substrates was evaluated as 0.2 ~ 0.4 nmRa in (100), (110) and (111) crystal planes. The LEED (low-energy electron diffraction) patterns indicated the almost perfect crystallographic structure without the residual processed strain beneath the polished surface. In this paper, the optimum Polishing condition to achieve the atomic-scale planarization of the diamond substrates has been investigated by the evaluation of LEED patterns, Wyko and AFM images. The mechanismof the ultraviolet rays assisted Polishing is discussed in detail.
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Study on Ultra Precision Polishing of Single Crystal Diamond Substrates under Ultraviolet Irradiation
Key Engineering Materials, 2009Co-Authors: Satoru Anan, Mutsumi Touge, Akihisa Kubota, Junji WatanabeAbstract:The ultraviolet irradiation-assisted ultra precision Polishing was performed on single crystal diamond substrates. This Polishing method has been newly developed in our laboratory. The change of Polishing performances was investigated by the presence of the UV irradiation. The polished surfaces were evaluated by the observation with WYKO. The experimental results are as follows; Surface roughness of diamond substrates polished under UV irradiation has become clearly smoother than that without UV irradiation. The surface roughness by this Polishing method was reached to be 0.19 nm Ra on (100) surface of single crystal diamond. The equivalent surface was obtained on (110) surface by the UV-Polishing.
Chi Fai Cheung - One of the best experts on this subject based on the ideXlab platform.
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Numerical modeling and experimentation of three dimensional material removal characteristics in fluid jet Polishing
International Journal of Mechanical Sciences, 2017Co-Authors: Chunjin Wang, Chi Fai CheungAbstract:Abstract Fluid jet Polishing is a promising Ultra-Precision Polishing technology which has been successfully used in Polishing various kinds of precision components. The characterization of the material removal plays an important role in deterministic Ultra-Precision Polishing process, which not only helps to better understand its material removal characteristics, but is also used to predict the material removal and help to determine the dwell time needed at different positions of the workpiece. During the fluid jet Polishing process, both vertical and oblique Polishing modes are often used for different purposes. However, currently published researches about the modeling of fluid jet Polishing are usually focused on the vertical impinging mode. Relatively few attentions have been paid to model the material removal in oblique impinging mode, whose material removal profile is asymmetric. As a result, this paper attempts to present a universal three dimensional numerical model (U3DNM) which can be used to model the fluid jet Polishing process both in vertical and oblique impinging modes. The U3DMN is built based on the computational fluid dynamic modelling method. Four groups of simulations and Polishing experiments were also conducted under various conditions so as to test the feasibility and reliability of this model. The results infer that the proposed numerical model is effective and has high robustness under various conditions. The successful development of the U3DNM provides a better understanding of the material removal characteristics which shed some light for better understanding and analysis of material removal for freeform surfaces which possesses continuous variation of curvatures.
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Stiffness modeling and optimization of a 3-DOF parallel robot in a serial-parallel Polishing machine
International Journal of Precision Engineering and Manufacturing, 2017Co-Authors: Peng Xu, Chi Fai Cheung, Bing Li, Jufan ZhangAbstract:Polishing is a kind of finishing process that can effectively reduce the surface defects and improve the form accuracy. This paper presents a novel hybrid machine with 6 degrees of freedom (DOF) serial-parallel topological structure used as an Ultra-Precision Polishing equipment which is composed of a 3-DOF parallel robot, a 2-DOF serial robot and a turntable providing a redundant DOF. Due to the complexity of structure, stiffness performance evaluation of the parallel robot becomes a challenge. As a result, a theoretical model of the parallel robot based on the virtual work principle and the deformation superposition principle is formulated for analyzing the stiffness performance. With the developed model, a multi-objective dimensional optimization method is developed to maximize both the workspace volume and the global stiffness performance of the parallel robot. Artificial intelligence approach based on genetic algorithms is implemented to obtain an optimal combination of structural parameters. The effectiveness of this method is validated by simulation and the parallel robot with optimized structural parameters has a workspace with higher stiffness performance, hence justifies its suitability for high precision Polishing.
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An Investigation of Factors Affecting and Optimizing Material Removal Rate in Computer Controlled Ultra-Precision Polishing
Key Engineering Materials, 2014Co-Authors: Lai Ting Ho, Chi Fai Cheung, Liam Blunt, Sheng Yue ZengAbstract:There are numerous parameters and steps involved in a computer controlled Ultra-Precision Polishing process (CCUP). The success of CCUP relies heavily on the understanding and optimization of material removal when new materials and new surfaces are polished. It is crucial to optimize the Polishing parameters to enhance the effectiveness of the Polishing process and to assess the impact of different process parameters on the material removal rate of particular difficult-to-machine materials such as CoCr alloys, which is commonly used in orthopedic implants. This paper aims at studying the process parameters and optimization of the parameter to enhance the material removal rate and quantify the contribution of process parameters.
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An integrated approach for design, ultraprecision Polishing, and measurement of freeform progressive lenses
6th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Advanced Optical Manufacturing Technologies, 2012Co-Authors: Chi Fai Cheung, L.b. Kong, L.t. Ho, Sandy To, Bo WangAbstract:The importance of presbyopia is that it affects 100% of people at their late adulthood and it starts to show up at 40s. The market for high quality progressive lenses is very large. There is a growing need for freeform progressive lenses with a small interval of degree to provide a clear and comfortable intermediate vision for presbyopic patients. Due to the lack of adequate design and manufacturing capability, most of the freeform progressive lenses are designed and imported from overseas at a high price and with long delivery time. This paper presents an integrated approach for supporting design, fabrication and measurement of freeform progressive lenses. A prototype of an integrated system has been developed based on key technologies including an advanced optics design method, computer controlled Ultra-Precision Polishing (CCUP), precision injection moulding, as well as a new freeform surface characterization method. A prototype system has been built and experimental verified successfully through a series of experiments. Successful development of the system will provide an important means for optometry research of freeform progressive lenses.
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A study of characterisation of surface generation in Ultra-Precision Polishing using power spectrum analysis
International Journal of Nanomanufacturing, 2012Co-Authors: L.t. Ho, Chi Fai CheungAbstract:This paper aims to characterise the surface generation in Ultra-Precision Polishing using power spectrum analysis. The surface characteristics of mechanical polished surfaces and fluid jet polished surfaces are extracted, decomposed and analysed by power spectrum analysis of their surface roughness profiles. It is found that the surface roughness in both mechanical Polishing and fluid jet Polishing is mainly composed of low frequency components. With the aid of power spectrum analysis, it is also observed that the capability of machine signature removal and surface structure modification of fluid jet Polishing are less effective than in mechanical Polishing.
Xu Wang - One of the best experts on this subject based on the ideXlab platform.
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Laser Induced Damage of Potassium Dihydrogen Phosphate (KDP) Optical Crystal Machined by Water Dissolution Ultra-Precision Polishing Method
Materials, 2018Co-Authors: Yuchuan Chen, Xu WangAbstract:Laser induced damage threshold (LIDT) is an important optical indicator for nonlinear Potassium Dihydrogen Phosphate (KDP) crystal used in high power laser systems. In this study, KDP optical crystals are initially machined with single point diamond turning (SPDT), followed by water dissolution Ultra-Precision Polishing (WDUP) and then tested with 355 nm nanosecond pulsed-lasers. Power spectral density (PSD) analysis shows that WDUP process eliminates the laser-detrimental spatial frequencies band of micro-waviness on SPDT machined surface and consequently decreases its modulation effect on the laser beams. The laser test results show that LIDT of WDUP machined crystal improves and its stability has a significant increase by 72.1% compared with that of SPDT. Moreover, a subsequent ultrasonic assisted solvent cleaning process is suggested to have a positive effect on the laser performance of machined KDP crystal. Damage crater investigation indicates that the damage morphologies exhibit highly thermal explosion features of melted cores and brittle fractures of periphery material, which can be described with the classic thermal explosion model. The comparison result demonstrates that damage mechanisms for SPDT and WDUP machined crystal are the same and WDUP process reveals the real bulk laser resistance of KDP optical crystal by removing the micro-waviness and subsurface damage on SPDT machined surface. This improvement of WDUP method makes the LIDT more accurate and will be beneficial to the laser performance of KDP crystal.
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Water dissolution Ultra-Precision Polishing of KDP crystal and its precision cleaning
International Journal of Nanomanufacturing, 2018Co-Authors: Yuchuan Chen, Xu Wang, Xiaoji TengAbstract:KDP crystal is a kind of excellent electro-optic material used in many laser facilities, which is also widely acknowledged to be extremely hard to machine. In this work, we developed a process to finish KDP crystal to a precision and clean engineering specimen. A micro-nano water dissolution principle and its planarisation mechanism in the machining process are illustrated, which turns the disadvantaged deliquescence property of KDP crystal into the driving force for Ultra-Precision Polishing of the crystal. Micro emulsion fluid with nano water nuclei can precisely control the material removal and realize the selective Polishing, thus forming a super smooth and precise surface. Then a subsequent cleaning process developed specially for this Ultra-Precision Polishing method helps to get rid of the Polishing fluid, and finally reduces the residue off the crystal to a clean and tidy surface with 1.964 nm rms roughness for engineering application.
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Experimental Study on Micro-Deliquescence Ultra-Precision Polishing with Fine Water Mist for KDP Crystal
Advanced Materials Research, 2013Co-Authors: Xu Wang, Yuchuan Chen, C.p. SongAbstract:KDP crystal (Potassium dihydrogen phosphate single crystal) is extremely difficult to obtain flawless surface because of its soft, brittle, and hygroscopic. And a large amount of time has been spend on obtaining flawless surface with Ultra-Precision machining methods. In order to quickly reduce surface roughness on KDP crystal, a new micro-deliquescence Polishing method with fine water mist was proposed, the Polishing tool with fine water mist was designed, and the Polishing experiment was carried out. The micro-deliquescence Polishing with fine water mist can improve the surface quality of KDP crystal quickly, so it is an effective preprocessing before Ultra-Precision machining.
Yuchuan Chen - One of the best experts on this subject based on the ideXlab platform.
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Laser Induced Damage of Potassium Dihydrogen Phosphate (KDP) Optical Crystal Machined by Water Dissolution Ultra-Precision Polishing Method
Materials, 2018Co-Authors: Yuchuan Chen, Xu WangAbstract:Laser induced damage threshold (LIDT) is an important optical indicator for nonlinear Potassium Dihydrogen Phosphate (KDP) crystal used in high power laser systems. In this study, KDP optical crystals are initially machined with single point diamond turning (SPDT), followed by water dissolution Ultra-Precision Polishing (WDUP) and then tested with 355 nm nanosecond pulsed-lasers. Power spectral density (PSD) analysis shows that WDUP process eliminates the laser-detrimental spatial frequencies band of micro-waviness on SPDT machined surface and consequently decreases its modulation effect on the laser beams. The laser test results show that LIDT of WDUP machined crystal improves and its stability has a significant increase by 72.1% compared with that of SPDT. Moreover, a subsequent ultrasonic assisted solvent cleaning process is suggested to have a positive effect on the laser performance of machined KDP crystal. Damage crater investigation indicates that the damage morphologies exhibit highly thermal explosion features of melted cores and brittle fractures of periphery material, which can be described with the classic thermal explosion model. The comparison result demonstrates that damage mechanisms for SPDT and WDUP machined crystal are the same and WDUP process reveals the real bulk laser resistance of KDP optical crystal by removing the micro-waviness and subsurface damage on SPDT machined surface. This improvement of WDUP method makes the LIDT more accurate and will be beneficial to the laser performance of KDP crystal.
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Water dissolution Ultra-Precision Polishing of KDP crystal and its precision cleaning
International Journal of Nanomanufacturing, 2018Co-Authors: Yuchuan Chen, Xu Wang, Xiaoji TengAbstract:KDP crystal is a kind of excellent electro-optic material used in many laser facilities, which is also widely acknowledged to be extremely hard to machine. In this work, we developed a process to finish KDP crystal to a precision and clean engineering specimen. A micro-nano water dissolution principle and its planarisation mechanism in the machining process are illustrated, which turns the disadvantaged deliquescence property of KDP crystal into the driving force for Ultra-Precision Polishing of the crystal. Micro emulsion fluid with nano water nuclei can precisely control the material removal and realize the selective Polishing, thus forming a super smooth and precise surface. Then a subsequent cleaning process developed specially for this Ultra-Precision Polishing method helps to get rid of the Polishing fluid, and finally reduces the residue off the crystal to a clean and tidy surface with 1.964 nm rms roughness for engineering application.
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Experimental Study on Micro-Deliquescence Ultra-Precision Polishing with Fine Water Mist for KDP Crystal
Advanced Materials Research, 2013Co-Authors: Xu Wang, Yuchuan Chen, C.p. SongAbstract:KDP crystal (Potassium dihydrogen phosphate single crystal) is extremely difficult to obtain flawless surface because of its soft, brittle, and hygroscopic. And a large amount of time has been spend on obtaining flawless surface with Ultra-Precision machining methods. In order to quickly reduce surface roughness on KDP crystal, a new micro-deliquescence Polishing method with fine water mist was proposed, the Polishing tool with fine water mist was designed, and the Polishing experiment was carried out. The micro-deliquescence Polishing with fine water mist can improve the surface quality of KDP crystal quickly, so it is an effective preprocessing before Ultra-Precision machining.
Suet To - One of the best experts on this subject based on the ideXlab platform.
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Advances in Ultra-Precision machining of micro-structured functional surfaces and their typical applications
International Journal of Machine Tools & Manufacture, 2019Co-Authors: Shaojian Zhang, Yuanping Zhou, Haijun Zhang, Zhiwen Xiong, Suet ToAbstract:Abstract Micro-structured functional surfaces have achieved widespread applications in various advanced scientific, technological, industrial, and engineered fields due to their excellent performances, which are vitally limited by their feasible fabrication. Currently, Ultra-Precision machining, typically including Ultra-Precision diamond turning, Ultra-Precision diamond milling, Ultra-Precision diamond scratching, Ultra-Precision grinding, and Ultra-Precision Polishing, is developed as a very-promising solution for the micro-structured functional surface fabrication with high quality, high efficiency, high flexibility, and low cost. Therefore, this paper aims to briefly review the current state of the art in the investigation into Ultra-Precision machining characteristics of micro-structured functional surfaces with a focus on their typical advanced applications as the significant achievements of their Ultra-Precision machining fabrication, discuss the key challenges, and further provide new insights into Ultra-Precision machining of micro-structured functional surfaces for the future research and their further advanced applications.
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Modelling and simulation of structure surface generation using computer controlled Ultra-Precision Polishing
Precision Engineering-journal of The International Societies for Precision Engineering and Nanotechnology, 2011Co-Authors: Chi Fai Cheung, Lai Ting Ho, L.b. Kong, Suet ToAbstract:Abstract The applications of structured surfaces have been more widespread. However, research on the fabrication of these surfaces is still far from complete. The paper presents a theoretical and experimental investigation of the generation of structured surfaces by using Computer Controlled Ultra-Precision Polishing (CCUP). A surface topography simulation model and hence a model-based simulation system for the modelling and simulation of the generation of structure surfaces by using CCUP have been established and verified through a series of simulation and practical Polishing experiments. The results of experiments demonstrate the capability of the model-based simulation system in predicting the form error and the pattern of the 3D-texture generated by using CCUP.
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An experimental investigation of surface generation using an integrated Ultra-Precision Polishing process and different Polishing trajectories
Proceedings of the Institution of Mechanical Engineers Part B: Journal of Engineering Manufacture, 2011Co-Authors: Ho, Chi Fai Cheung, Suet ToAbstract:Ultra-Precision freeform Polishing (UPFP) is an emerging technology for the machining of Ultra-Precision freeform surfaces with submicrometre form accuracy and surface roughness in the nanometre ra...
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A Study of Wear Characteristics of Superpolished Orthopaedic Implant Materials Using Ultra-Precision Polishing
Key Engineering Materials, 2010Co-Authors: Chi Fai Cheung, P. Charlton, Suet ToAbstract:Ultra-Precision Polishing is an emerging technology for producing superfinishing surfaces with sub-micrometer form accuracy and surface finish in nanometer range. It has been applied in superPolishing the freeform bearing surfaces of orthopaedic implants. It is believe that the superfinished surfaces are capable of prolonging the life of the implants. In this paper, an experimental investigation of Ultra-Precision Polishing of orthopaedic implants and the study of the wear characteristics of the superfinished surfaces using a multi-directional pin-on-plate wear test simulator are implemented. Tests were carried out over 3 million cycles using Zeeko IRP200 superfinished cobalt chrome pins articulating against cross-linked UHMWPE plates. The results were compared to that of manually polished pins articulated against the same UHMWPE material. The results show that the Zeeko IRP200 polished pins produced better wear performance that that of the manually polished pins.
