ABSTRACT The polishing stocks used in various ultra-precision polishing machines consist of abrasives, polishing disk (pad), and polishing fluids. They are expendable goods. To ensure the machining ability and the repeat accuracy of machining characteristics, the polishing disc (pad) must use the dressing mechanism to produce sharp new grains. As a result, the grinding surface on the abrasive wheel becomes thinner gradually, then losses it¡¦s machining ability, and finally must be changed. Hence, in this project, an idea of an ultra-precision abrasive machining is proposed by using the continuous composite electroplating on the polishing disc. In this idea, the machining ability of Cu polishing disc can be ensured due to the use of the continuous Sn-Al2O3 composite electroplating. Hence, it can save the cost of the ultra-precision machining using in the semiconductor wafer. In this study, after 60 minutes continuous composite electroplated polishing, the thickness of the composite coating on the surface of Cu polishing disc can increase 6.13£gm. It means the surface of disc can be grew and renewed at every moment. The removal amount of the wafer is 10.8£gm. The surface of wafer was Ra=0.5453£gm and Rmax=5.464£gm at the start ,but came to Ra=0.0019£gm and Planess=2.649£gm/36mm after 60 minutes polishing.

In conventional abrasive machining , it must using dresser to dress the surface of polishing disc periodically , in order for polishing disc to maintain its ability of machining , and then ensuring the quality of work piece. It will make polishing disk thin , finally it must losing it ability of machining , and then be replaced by a new disc. For this reason , in the study , an idea of a new type ultraprecision polisher is proposed . Using Sn-Al2O3 composite coating to reach the mirror surface grinding of silicon wafer in the tin bath , and grinding with electroplating continuously . It will ensure the ability of machining of polishing disc . In the study , first , analyzing the effect of rotational speed rate of wafer and polishing disc on the grinding trajectories type of machining surface . From the result of analysis , find that , when the rotational speed rate is more irregular or it could not divided , the arrangement of grinding trajectories is more complex . And then , investigating the effect of cathode current density , rotational speed of polishing disc and time of plating on the characteristics of composite coating . In the experiment of composite electroplating , when cathode current density is higher , the size of crystal is smaller , the thickness of coating is thicker , and the quantity of Al2O3 within coating decrease lightly . The increase of the rotational speed of polishing disk could increase the size of crystal , the thickness of coating and the quantity of Al2O3 lightly . The time of plating is longer , the shape of crystal is more obvious , the thickness of coating is thicker and it also increase the quantity of Al2O3 . Finally , investigating the effect of cathode current density and cationic surfactant PEI on the characteristics of coating and wafer . In practical abrasive machining , the removal rate of wafer increases with cathode current density , and the addition of PEI could increase the quantity of Al2O3 indeed . Besides , under the same machining condition , in the tin bath with PEI , the removal rate is higher than the one in the tin bath without PEI .

No description available.

Classical fabrication methods alone do not enable manufacturing of large flat mirrors that are much larger than 1 meter. This dissertation presents the development of enabling technologies for manufacturing large high performance flat mirrors and lays the foundation for manufacturing very large flat mirrors. The enabling fabrication and testing methods were developed during the manufacture of a 1.6 meter flat. The key advantage over classical methods is that our method is scalable to larger flat mirrors up to 8 m in diameter.Large tools were used during surface grinding and coarse polishing of the 1.6 m flat. During this stage, electronic levels provided efficient measurements on global surface changes in the mirror. The electronic levels measure surface inclination or slope very accurately. They measured slope changes across the mirror surface. From the slope information, we can obtain surface information. Over 2 m, the electronic levels can measure to 50 nm rms of low order aberrations that include power and astigmatism. The use of electronic levels for flatness measurements is analyzed in detail.Surface figuring was performed with smaller tools (size ranging from 15 cm to 40 cm in diameter). A radial stroker was developed and used to drive the smaller tools; the radial stroker provided variable tool stroke and rotation (up to 8 revolutions per minute). Polishing software, initially developed for stressed laps, enabled computer controlled polishing and was used to generate simulated removal profiles by optimizing tool stroke and dwell to reduce the high zones on the mirror surface. The resulting simulations from the polishing software were then applied to the real mirror. The scanning pentaprism and the 1 meter vibration insensitive Fizeau interferometer provided accurate and efficient surface testing to guide the remaining fabrication. The scanning pentaprism, another slope test, measured power to 9 nm rms over 2 meters. The Fizeau interferometer measured 1 meter subapertures and measured the 1.6 meter flat to 3 nm rms; the 1 meter reference flat was also calibrated to 3 nm rms. Both test systems are analyzed in detail. During surface figuring, the fabrication and testing were operated in a closed loop. The closed loop operation resulted in a rapid convergence of the mirror surface (11 nm rms power, and 6 nm rms surface irregularity). At present, the surface figure for the finished 1.6 m flat is state of the art for 2 meter class flat mirrors.

No description available.

No description available.

No description available.

Production of micro-scale components is an important emergent field. One underdeveloped area is the production of micro-scale 3D surfaces, which has important applications in micro-optics and fibre optic sensors. One particular application is the production of micro-lenses. With scales of less than 200 ??m these lenses can improve light coupling efficiencies in micro-optic systems. However, current lens production techniques have limitations in accuracy and versatility. Creating these surfaces through mechanical micro-grinding has the potential to improve the precision and variety of profiles that can be produced, thus improving transmission efficiencies and leading to new applications. This work presents a novel micro-grinding method for the production of microscale asymmetric, symmetric and axisymmetric curved components from brittle materials such as glasses. A specialised micro-grinding machine and machining system has been designed, constructed and successfully tested and is presented here. This system is capable of producing complex profiles directly on the tips of optical fibre workpieces. A five degree of freedom centring system is presented that can align and rotate these workpieces about a precision axis, enabling axisymmetric grinding. A machine vision system, utilising a microscope lens system and sub-pixel localisation techniques, is used to provide feedback for the process, image processing techniques are presented which are shown to have a sensing resolution of 300 nm. Using these systems, workpieces are centred to within 500 nm. Tools are mounted on nanometre precise motion stages and motion and infeed are controlled. Tooling configurations with flat and tangential grinding surfaces are presented along with control and path generation algorithms. The capabilities and shortcomings of each are presented along with methods to predict appropriate feed rates based on experimental data. Both asymmetric and axisymmetric flat and curved micro-profiles have been produced on the tips of optical fibres using this system. These are presented and analysed and show that the system, as described, is capable of producing high quality micro-scale components with submicron dimensional accuracy and nanometric surface quality. The advantages of this technique are compared with other processes and discussed. Further development of the system and technique are also considered.

Thesis (M. Phil.)--University of Hong Kong, 2008. / Also available in print.

Thesis (M.S.)--University of Wisconsin--Madison, 1968. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.