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.

Thesis (Ph. D.)--Chemical Engineering, Georgia Institute of Technology, 2006. / Samuels, Robert J., Committee Member ; Henderson, Clifford L., Committee Member ; Danyluk, Steven, Committee Member ; Hess, Dennis W., Committee Chair ; Bottomley, Lawrence A., Committee Member ; Morris, Jeffrey F., Committee Co-Chair. Vita. Includes bibliographical references.

Orientador: Eduardo Carlos Bianchi / Co-orientador: Vicente Luiz Scalon / Resumo: O processo de retificação é um processo de usinagem por abrasão que visa principalmente obtenção de superfícies com baixa rugosidade e tolerância dimensional estreita. Essa combinação é possível por causa das múltiplas arestas de corte sem geometria definida que removem material da peça em pequenas penetrações de trabalho. Contudo é um processo que apresenta problemas para a peça, devido à elevada geração de calor. Este calor pode causar alterações metalúrgicas, dentre outras. Por esta razão é necessário utilizar fluido de corte para refrigerar a zona de retificação. Ao mesmo tempo é preciso buscar uma produção mais sustentável em relação à técnica de lubri-refrigeração convencional. Esta técnica vem sendo substituída por outras que visam redução de custo e redução e/ou eliminação do impacto ambiental, sem prejuízos para qualidade da peça. Uma técnica de lubri-refrigeração que vem substituindo a técnica convencional competitivamente é a técnica de Mínima Quantidade de Lubrificação (MQL), que é bem difundida em processos de usinagem com geometria de corte definida (por exemplo, torneamento, fresamento e furação) e com resultados promissores também em processos de retificação. Entretanto, pelo fato da técnica MQL ser menos estudada no processo de retificação, seu desempenho ainda apresenta algumas restrições devido à sua baixa eficiência de refrigeração, que pode ocasionar danos térmicos à peça. Neste sentido, a realização deste trabalho consistiu em substituir o ar à temperatu... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The grinding process is an abrasion machining process that is mainly aimed at obtaining surfaces with low roughness and narrow dimensional tolerance. This combination is possible because of the multiple cutting edges without defined geometry that remove material from the workpiece at small work penetrations. However, it is a process that presents problems for the workpiece, due to the high generation of heat. This heat can cause metallurgical changes, among others. For this reason it is necessary to use cutting fluid to cool the grinding zone. At the same time it is necessary to seek a more sustainable production compared to the conventional lubri-cooling technique. This technique has been replaced by others that aim at cost reduction and reduction and/or elimination of environmental impact, without any damage to the quality of the part. A lubri-cooling technique that is replacing the conventional technique, competitively, is the Minimum Quantity of Lubricant (MQL) technique, which is well diffused in machining processes with defined cutting geometry (for example, turning, milling and drilling) and with promising results also in grinding processes. However, due the MQL technique is less studied in the grinding process, its performance still presents some restrictions due to its low cooling efficiency, which can cause thermal damage to the part. In this sense, the accomplishment of this work consisted in replacing the air at the ambient temperature of the MQL by air at a lower... (Complete abstract click electronic access below) / Mestre