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Pedder, James Edward Alexander. "Laser machining for microsystems." Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.506039.
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Raghavan, Satyanarayanan. "Laser-based hybrid process for machining hardened steels." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/47550.
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Cost-effective machining of hardened steel (>60 HRC) components such as a large wind turbine bearing poses a significant challenge. This thesis investigates a new laser tempering based hybrid turning approach to machine hardened AISI 52100 steel parts more efficiently and cost effectively. The approach consists of a two step process involving laser tempering of the hardened workpiece surface followed by conventional machining at higher material removal rates using lower cost ceramic tooling to efficiently cut the laser tempered material.
The specific objectives of this work are to: (a) study the characteristics of laser tempering of hyper-eutectoid 52100 hardened steel, (b) model the laser tempering process to determine the resulting hardness, and (c) conduct machining experiments to evaluate the performance of the laser tempering based hybrid turning process in terms of forces, tools wear and surface finish.
First, the microstructure alterations and phase content in the surface and subsurface layers are analyzed using metallography and x-ray diffraction (XRD) respectively. Laser tempering produces distinct regions consisting of - a tempered white layer and a dark layer- in the heat affected subsurface region of the workpiece. The depth of the tempered region is dependent on the laser scanning conditions. Larger overlap of laser scans and smaller scan speeds produce a thicker tempered region. Furthermore, the tempered region is composed of ferrite and martensite and weak traces of retained austenite (~ 1 %).
Second, a laser tempering model consisting of a three dimensional analytical model to predict the temperature field generated by laser scanning of 52100 hardened steel and a phase change based hardness model to predict the hardness of the tempered region are developed. The thermal model is used to evaluate the temperature field
induced in the subsurface region due to the thermal cycles produced by the laser scanning step. The computed temperature histories are then fed to the phase change model to predict the surface and subsurface hardness. The laser tempering model is used to select the laser scanning conditions that yield the desired hardness reduction at the maximum depth. This model is verified through laser scanning experiments wherein the hardness changes are compared with model predictions. The model is shown to yield predictions that are within 20 % of the measured hardness of the tempered region.
Using the laser scanning parameters determined from the laser tempering model, cutting experiments using Cubic Boron Nitride (CBN) tools and low cost alumina ceramic tools are conducted to compare the performance of laser tempering based hybrid turning with the conventional hard turning process. The machining experiments demonstrate the possibility of higher material removal rates, lower cutting forces, improved tool wear behavior, and consequently improved tool life in the laser tempering based process. In addition, the laser tempered based hybrid turning process produce is shown to yield lower peak-to-valley surface roughness height than the conventional hard turning process. Furthermore, it is found that lower cost ceramic tools can be used in place of CBN tools without compromising the material removal rate.
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Bin, Ahmad Sabli Ahmad Syamaizar. "Ultrashort pulsed laser machining of Ti6Al4VAlloy." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/ultrashort-pulsed-laser-machining-of-ti6al4valloy(a01ab696-e895-431c-944d-1c7cd94420f5).html.
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Machining of hard metal alloys such as Ti6Al4V alloys with cutting tools incurs high cost particularly in the replacement of worn out tools. In light of this, lasers offer a non-contact processing method which could potentially reduce costs. Lasers can introduce undesirable processing effects, but with the emergence of high powered ultrashort lasers, these processing defects can be greatly reduced. To date, there have been limited studies conducted within the area of picosecond laser machining process. This research has two primary objectives. Firstly, using lasers as an alternative to mechanical processes. Secondly, using a picosecond laser in machining of Ti6Al4V alloy to maximise material removal rate and minimise defects. In this study, an Nd:YVO4 Edge wave picosecond pulsed laser was used for machining Ti6Al4V alloy in air and at room temperature and pressure to understand laser interaction with the Ti6Al4V alloy. The laser was rated at 300W with up to 20 MHz repetition rate and up to 10 m/s scanning rate. Design of experiments was used to understand the effects of varying laser parameters and establishing the ablation threshold. Once the process parameters were established, the next stage was aimed at improving the material removal rates through various strategies. To understand the material removal process, a state of the art holography method was utilised to visualise the laser material interaction. This research has produced three significant results. It was established that the ablation threshold was 45 mJ/cm2 for picosecond laser machining of Ti6Al4V alloy. For the first time in this field of research, the optimal material removal was achieved when the laser was focused at 15 mm above the sample surface resulting in an improvement from 0.1 to 0.6 mm3/min. The holography visualisation revealed that the material removal rate was significantly reduced as the number of pulses increased due to the presence of plasma. Findings of this research support the future of picosecond laser machining of hard metals for micro as well as macro scale applications. Some of the relevant industries for this area of research include aerospace manufacture, automotive parts manufacturing and even manufacture of personal items such as watches, eye wear and jewellery.
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Pajak, Przemyslaw T. "Investigation of laser assisted electrochemical machining." Thesis, Glasgow Caledonian University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426411.
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SANTOS, ROBERTO de B. "Microfuracao com laser pulsado." reponame:Repositório Institucional do IPEN, 2001. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10900.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Tavakoli, Manshadi Salar. "Laser assisted machining of Inconel 718 superalloy." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40803.
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This research work assesses the effect of Laser Assisted Machining (LAM) on the machinability of Inconel 718 using a triple layer coated carbide and a sialon ceramic tool. This study was motivated by issues related to poor machinability of IN718 under conventional machining operations. In this work a focused Nd:YAG laser beam was used as a localized heat source to thermally soften the workpiece prior to material removal. Finishing operations were assumed throughout the experiments. Optimization screening tests were performed over a wide range of cutting speeds (ranging from 100 to 500 m/min) and feeds (ranging from 0.125 to 0.5 mm/rev). Results showed a significant drop in all three components of cutting force when thermal softening caused by the laser power was in effect. These tests yielded the optimum cutting speed and feed to be 200 m/min and 0.25 mm/rev for the coated carbide and 300 m/min and 0.4 mm/rev for the ceramic tool. Under these optimum conditions tool life tests were carried out. Drastic increase in terms of the material removal rate (MRR) was demonstrated under LAM conditions as compared to conventional machining. A nearly %300 increase in MRR was established for the coated carbide tool while slightly reducing tool life, mainly because the coatings offering thermal and wear protection could not withstand the high temperatures associated with LAM. Nearly %800 increase in MRR for the ceramic tool was achieved while improving tool life (about %50). In all cases, improvements in surface finish and surface integrity were observed. The dominant mode of tool failure was observed to be average flank wear for all tools tested. However, the coated carbide tool exhibited signs of chipping and flaking in the coatings. The morphology of the chips produced was analyzed and it was shown that temperature and increased chip thickness were the main causes of transition from steady state to shear localized chip structure. Shear localized or sawtooth chips tended toCette recherche évalue l'effet de l’usinage assisté par Laser (UAL) sur l’usinabilité d'Inconel 718 en utilisant deux outils : Le premier est enrobé d’une triple couche de carbure et le second est en céramique sialon. Cette étude a été motivée par la difficulté d’usiner IN718 conventionnellement. Dans ce travail, un rayon laser Nd:YAG a été utilisé comme une source de chaleur localisée pour adoucir thermiquement la pièce avant l'usinage. Les expériences représentaient les opérations de finitions. Une optimisation a été exécutée à travers une sélection unitaire pour une large gamme de vitesses de coupes (aux limites de 100 à 500 m/min) et de vitesses d’avance (aux limites de 0.125 à 0.5 mm/rév). Les résultats ont manifesté une réduction significative dans toutes les trois composantes de la force de coupe quand l'adoucissement thermique provoqué par le laser était mis en effet. D’après les tests, les valeurs optimales de vitesse de coupe et d’avance sont 200 m/min et 0.25 mm/rév pour l’outil avec la couche de carbure et 300 m/min et 0.4 mm/rév pour l’outil en céramique. Dans ces conditions optimales, des épreuves de tenue d’outils ont été réalisées. Une augmentation du taux d’enlèvement de matière a été démontrée lors de l’application de l’UAL en comparaison à l’usinage conventionnel. Une augmentation dans le taux d’enlèvement de matière de 300% a été établie pour l’outil enrobé de carbure avec une légère réduction en tenue d’outil. La raison de cette réduction est le fait que ces couches qui offrent une protection thermique et une résistance d’usure ne pouvaient pas résister aux températures élevées associées à l’UAL. Une augmentation de 800% dans le taux d’enlèvement de matière a été accomplie pour l’outil en céramique avec une amélioration de tenue d’outils d’environ 50%. Dans tous les cas, une amélioration de l’intégrité de la surface à ét
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Yan, Yinzhou. "High-quality laser machining of alumina ceramics." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/highquality-laser-machining-of-alumina-ceramics(3dd60fb6-5bda-4cc9-8f00-f49b170ca6aa).html.
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Alumina is one of the most commonly used engineering ceramics for a variety of applications ranging from microelectronics to prosthetics due to its desirable properties. Unfortunately, conventional machining techniques generally lead to fracture, tool failure, low surface integrity, high energy consumption, low material removal rate, and high tool wear during machining due to high hardness and brittleness of the ceramic material. Laser machining offers an alternative for rapid processing of brittle and hard engineering ceramics. However, the material properties, especially the high thermal expansion coefficient and low thermal conductivity, may cause ceramic fracture due to thermal damage. Striation formation is another defect in laser cutting. These drawbacks limit advanced ceramics in engineering applications. In this work, various lasers and machining techniques are investigated to explore the feasibility of high-quality laser machining different thicknesses of alumina. The main contributions include: (i) Fibre laser crack-free cutting of thick-section alumina (up to 6-mm-thickness). A three-dimensional numerical model considering the material removal was developed to study the effects of process parameters on temperature, thermal-stress distribution, fracture initiation and propagation in laser cutting. A rapid parameters optimisation procedure for crack-free cutting of thick-section ceramics was proposed. (ii) Low power CW CO2 laser underwater machining of closed cavities (up to 2-mm depth) in alumina was demonstrated with high-quality in terms of surface finish and integrity. A three-dimensional thermal-stress model and a two-dimensional fluid smooth particle hydrodynamic model (SPH) were developed to investigate the physical processes during CO2 laser underwater machining. SPH modelling has been applied for the first time to studying laser processing of ceramics. (iii) Striation-free cutting of alumina sheets (1-mm thickness) is realised using a nano-second pulsed DPSS Nd: YAG laser, which demonstrates the capability of high average power short pulsed lasers in high-quality macro-machining. A mechanism of pulsed laser striation-free cutting was also proposed. The present work opens up new opportunities for applying lasers for high-quality machining of engineering ceramics.
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Bredt, James Frederic. "Laser machining of ceramics and metals : development of a laser lathe." Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/38337.
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Salama, Adel. "Laser machining of carbon fibre reinforced polymer composite." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/laser-machining-of-carbon-fibre-reinforced-polymer-composite(7310ed95-b876-480b-a8b4-2033b4309cb6).html.
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Carbon fibre reinforced polymer (CFRP) composites have found a wide range of applications in the aerospace, marine, sports and automotive industries owing to their lightweight and acceptable mechanical properties compared to the commonly used metallic materials. The currently dominating method of machining CFRP is by mechanical means that has found many problems including extensive tool wear, fibre pull-out and delamination. Lasers as non-contact tools have been widely applied for cutting and drilling materials. However, machining of CFRP composites using lasers can be challenging due to inhomogeneity in the material properties and structures, which can lead to thermal damage such as charring, heat affected zones (HAZs), resin recession and delamination. In previous studies, Nd:YAG, diode pumped solid state (DPSS), CO2 (continuous wave), disk and fibre lasers were used in machining CFRP composites and the control of damage such as the size of heat affected zones (HAZ) and achieving comparable material removal rate with the mechanical processes remain a challenge. Most reported work showed a typical heat affected zone of 0.2-1.2 mm. The availability of short pulsed transversely excited atmospheric (TEA) CO2 lasers and ultra-short laser pulse sources such as picosecond lasers make it possible to improve the laser machining quality of CFRP materials. In this research, the machining of CFRP composites using a microsecond pulsed TEA CO2 laser, a state of the art high power picosecond laser and a 1 kW single mode fibre laser system was investigated. The yielded heat affected zone was less than < 25 µm for the TEA CO2 and the picosecond laser machining, although the material removal rate was low. Additionally, it has been shown that the pulsed fibre laser improved the machining quality compared to that with the continuous mode. A potential application of the fibre laser for composite repair and remanufacturing was investigated. The interactions between picosecond laser beam and CFRP composite were studied in more detail including understanding the self-limiting effect in single and multiple parallel tracks drilling/machining through both experimental and theoretical studies. Furthermore, a sequential laser and mechanical drilling of CFRP was investigated to improve the machining rate. The work performed in this PhD was driven by aerospace industry needs, with the collaboration of Rolls-Royce plc and BAE Systems as industrial partners.
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Armitage, Kelly, and n/a. "Laser assisted machining of high chromium white cast-iron." Swinburne University of Technology, 2006. http://adt.lib.swin.edu.au./public/adt-VSWT20070214.155302.
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Laser-assisted machining has been considered as an alternative for difficult-to-machine
materials such as metallic alloys and ceramics. Machining of some materials such as
high chromium alloys and high strength steels is still a delicate and challenging task.
Conventional machines or computer numerical control (CNC) machines and cutting
tools cannot adapt easily to such materials and induce very high costs for operations of
rough machining or finishing. If laser-assisted machining can be implemented
successfully for such materials, it will offer several advantages over the traditional
methods including longer tool life, shorter machining time and reduced overall costs.
This thesis presents the results of the research conducted on laser assisted machining of
hard to wear materials used in making heavy duty mineral processing equipment for the
mining industry. Experimental set up using a high power Nd:YAG laser beam attached
to a lathe has been developed to machine these materials using cubic boron nitride
(CBN) based cutting tools. The laser beam was positioned so that it was heating a point
on the surface of the workpiece directly before it passed under the cutting tool. Cutting
forces were measured during laser assisted machining and were compared to those
measured during conventional machining.
Results from the experiments show that with the right cutting parameters and laser beam
position, laser assisted machining results in a reduction in cutting forces compared to
conventional machining.
A mathematical thermal model was used to predict temperatures within the workpiece at
depths under the laser beam spot. The model was used to determine the effect of
various cutting and laser parameters on the temperature profile within the workpiece.
This study shows that laser assisted machining of hard to wear materials such as high
chromium white cast iron shows potential as a possible economical alternative to
conventional machining methods. Further research is needed before it can be
introduced in industry as an alternative to conventional machining.
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Shanmugam, Naveenkumar. "Machining of transparent brittle material by laser-induced seed cracks." Thesis, Kansas State University, 2015. http://hdl.handle.net/2097/20539.
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Master of ScienceIndustrial & Manufacturing Systems Engineering
Shuting Lei
Transparent brittle materials such as glass and silicon dioxide have begun to replace the conventional materials due to the advantageous properties including high strength and hardness, resistance to corrosion, wear, chemicals and heat, high electrical isolation, low optical absorption, large optical transmission range and biocompatibility. However because these materials are extremely hard and brittle, development of an ideal machining process has been a challenge for researchers. Non-traditional machining processes such as abrasive jet and ultrasonic machining have improved machining quality but these processes typically results with issues of poor surface integrity, high tool wear and low productivity. Therefore a machining technique that overcomes the disadvantages of existing methods must be developed. This study focused primarily on improving the machinability and attaining crack-free machined surfaces on transparent brittle materials by inducing micro cracks or seed damages on the subsurface of the materials. The hypothesis was that micro-cracks induced by femtosecond laser would synergistically assist the material removal process by a cutting tool by weakening or softening the material, followed by conventional machining process. Laser induced damages due to varying laser intensities and at different depths in bulk BK7 glass was studied in order to select the optimal laser machining conditions for the experiments. Dimensional and structural profiles of laser cracks are observed using an optical microscope. A comparative study of machined untreated BK7 samples and damage induced BK7 samples was conducted. Due to its simple process kinematics and tool geometry, orthogonal machining is used for the study. Results showed that machining laser-treated samples caused an average 75% force reduction on comparison to machining of untreated samples. Laser treated machined samples were produced without subsurface damages, and reduced tool wear was noted. Overall improved machinability of BK7 glass samples was achieved.
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Armitage, Kelly. "Laser assisted machining of high chromium white cast-iron." Australasian Digital Thesis Program, 2006. http://adt.lib.swin.edu.au/public/adt-VSWT20070214.155302/index.html.
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Thesis (MEng) - Swinburne University of Technology, Industrial Research Institute Swinburne - 2006.A thesis submitted in fulfillment of the requirement for the degree of Master of Engineering by Research, Industrial Research Institute Swinburne, Faculty of Engineering and Industrial Sciences, Swinburne University of Technology - 2006. Typescript. Includes bibliographical references (p. 113-116).
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Poonjolai, Erasenthiran. "Laser cutting, machining and welding for layered manufacturing applications." Thesis, University of Liverpool, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399289.
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ALMEIDA, IVAN A. de. "Otimização do processo de usinagem de titânio com laser pulsado de neodímio." reponame:Repositório Institucional do IPEN, 2007. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11589.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
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Singh, Ramesh K. "Laser Assisted Mechanical Micromachining of Hard-to-Machine Materials." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19803.
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There is growing demand for micro and meso scale devices with applications in the field of optics, semiconductor and bio-medical fields. In response to this demand, mechanical micro-cutting (e.g. micro-milling) is emerging as a viable alternative to lithography based micromachining techniques. Mechanical micromachining methods are capable of generating three-dimensional free-form surfaces to sub-micron level precision and micron level accuracies in a wide range of materials including common engineering alloys. However, certain factors limit the types of workpiece materials that can be processed using mechanical micromachining methods. For difficult-to-machine materials such as tool and die steels, limited machine-tool system stiffness and low tool flexural strength are major impediments to the use of mechanical micromachining methods.
This thesis presents the design, fabrication and analysis of a novel Laser-assisted Mechanical Micromachining (LAMM) process that has the potential to overcome these limitations. The basic concept involves creating localized thermal softening of the hard material by focusing a solid-state continuous wave laser beam of diameter ranging from 70-120 microns directly in front of a miniature (300 microns-1 mm wide) cutting tool. By suitably controlling the laser power, spot size and speed, it is possible to produce a sufficiently large decrease in flow stress of the work material and, consequently, the cutting forces. This in turn will reduce machine/tool deflection and chances of catastrophic tool failure. The reduced machine/tool deflection yields improved accuracy in the machined feature. In order to use this process effectively, adequate thermal softening needs to be produced while keeping the heat affected zone in the machined surface to a minimum. This has been accomplished in the thesis via a detailed process characterization, modeling of process mechanics and optimization of process variables.
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Bhatt, Deepa M. "Excimer laser machining of glass for high density substrate manufacture." Thesis, Loughborough University, 2009. https://dspace.lboro.ac.uk/2134/28103.
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The widely growing market of miniaturized electronic devices demands for alternative substrate materials and manufacturing technologies on which fine pitch components can be mounted. Glass has been identified as a potential substrate material as it offers a number of advantages including a coefficient of thermal expansion closely matched to that of silicon that may reduce the thermo-mechanical stresses on the interconnects in the flip-chip assemblies. In addition to this, its dimensional stability and optically transparent nature facilitates alignment of multiple layer structures, enabling accurate drilling of microvias to capture pads and the potential for applications in optical interconnect.
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Altman, Katrina J. "Microscale Machining and Mechanical Characterization of Bone Tissue." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1250522820.
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Heiderscheit, Timothy Donald. "Comparative study of near-infrared pulsed laser machining of carbon fiber reinforced plastics." Thesis, University of Iowa, 2017. https://ir.uiowa.edu/etd/5946.
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Carbon fiber-reinforced plastics (CFRPs) have gained widespread popularity as a lightweight, high-strength alternative to traditional materials. The unique anisotropic properties of CFRP make processing difficult, especially using conventional methods. This study investigates laser cutting by ablation as an alternative by comparing two near-infrared laser systems to a typical mechanical machining process. This research has potential applications in the automotive and aerospace industries, where CFRPs are particularly desirable for weight savings and fuel efficiency.
First, a CNC mill was used to study the effects of process parameters and tool design on machining quality. Despite high productivity and flexible tooling, mechanical drilling suffers from machining defects that could compromise structural performance of a CFRP component. Rotational feed rate was shown to be the primary factor in determining the axial thrust force, which correlated with the extent of delamination and peeling. Experimental results concluded that machining quality could be improved using a non-contact laser-based material removal mechanism.
Laser machining was investigated first with a Yb:YAG fiber laser system, operated in either continuous wave or pulse-modulated mode, for both cross-ply and woven CFRP. For the first time, energy density was used as a control variable to account for changes in process parameters, predicting a logarithmic relationship with machining results attributable to plasma shielding effects. Relevant process parameters included operation mode, laser power, pulse overlap, and cross-ply surface fiber orientation, all of which showed a significant impact on single-pass machining quality. High pulse frequency was required to successfully ablate woven CFRP at the weave boundaries, possibly due to matrix absorption dynamics. Overall, the Yb:YAG fiber laser system showed improved performance over mechanical machining. However, microsecond pulses cause extensive thermal damage and low ablation rates due to long laser-material interaction time and low power intensity.
Next, laser machining was investigated using a high-energy nanosecond-pulsed Nd:YAG NIR laser operating in either Q-Switch or Long Pulse mode. This research demonstrates for the first time that keyhole-mode cutting can be achieved for CFRP materials using a high-energy nanosecond laser with long-duration pulsing. It is also shown that short-duration Q-Switch mode results in an ineffective cutting performance for CFRP, likely due to laser-induced optical breakdown. At sufficiently high power intensity, it is hypothesized that the resulting plasma absorbs a significant portion of the incoming laser energy by the inverse Bremsstrahlung mechanism. In Long Pulse mode, multi-pass line and contour cutting experiments are further performed to investigate the effect of laser processing parameters on thermal damage and machined surface integrity. A logarithmic trend was observed for machining results, attributable to plasma shielding similar to microsecond fiber laser results. Cutting depth data was used to estimate the ablation threshold of Hexcel IM7 and AS4 fiber types. Drilling results show that a 2.2 mm thick cross-ply CFRP panel can be cut through using about 6 laser passes, and a high-quality machined surface can be produced with a limited heat-affected zone and little fiber pull-out using inert assist gas. In general, high-energy Long Pulse laser machining achieved superior performance due to shorter pulse duration and higher power intensity, resulting in significantly higher ablation rates. The successful outcomes from this work provide the key to enable an efficient high-quality laser machining process for CFRP materials.
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Dear, Fraser Craig. "Laser machining of medical grade Zirconia ceramic for dental reconstruction applications." Thesis, Heriot-Watt University, 2008. http://hdl.handle.net/10399/2139.
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The aim of this project is to provide a fundamental understanding of the processes involved in economically manufacturing complex component parts from medical grade Yttria Stabilised Zirconia. Such material is an attractive choice for many engineering applications, primarily due to its stiffness, hardness and wear resistance. Due to the hardness of the material however, conventional mechanical machining - especially at small micrometer scales - is difficult. As an alternative fabrication route this project investigated the precision limits of machining such ceramics using high power, pulsed lasers operating in millisecond, and nanosecond regimes and at wavelengths of 1075 nm, 1064 nm, 532 nm and 10.6 m. In order to establish the suitability of machined parts for biomedical implant, the use of a Raman Spectrometer was vital to establish the phases present in the final machined parts. The work focuses heavily on the use of Yttrium Oxide (Y2O3) Partially Stabilized Zirconia (PSZ) as it is the prime material used in dental reconstructions to date however a comparison with Alumina is carried out. In depth investigation of the processing parameters used in millisecond Nd:YAG and nanosecond Nd:YVO4 laser sources was conducted providing maximum material removal rates of 13 mm3/s and 2.1 mm3/min respectively. Successful CO2 laser processing was conducted on 8 mm thick samples however, when processing complex components, bulk failures were observed. An un-calibrated infrared camera was used in this process, highlighting potential thermal gradients responsible for bulk fracture. The particularly difficult process of blind hole drilling using a mechanical method has been investigated using a laser to pre-drill a suitable hole before mechanical machining takes place. This investigation has resulted in a 97% reduction in processing time using the developed laser process over the mechanical method used currently. Additionally, a dual laser process is examined in order to provide a two phase machining method utilising the speed and precision of two different lasers respectively. A novel high beam quality laser process is presented which offers a technique to section 14 mm thick samples of the material via a crack propagation method. Future research opportunities have been identified and discussed, focussing on ways to resolve these key issues and other possibilities in laser processing.
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Ali, Arham. "Chemo-Thermal Micromachining of Glass: An Explorative Study." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin154392221273875.
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Yu, Xiaoming. "Laser micro/nano machining based on spatial, temporal and spectral control of light-matter interaction." Diss., Kansas State University, 2016. http://hdl.handle.net/2097/32928.
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Doctor of PhilosophyDepartment of Industrial & Manufacturing Systems Engineering
Shuting Lei
Lasers have been widely used as a manufacturing tool for material processing, such as drilling, cutting, welding and surface texturing. Compared to traditional manufacturing methods, laser-based material processing is high precision, can treat a wide range of materials, and has no tool wear. However, demanding manufacturing processes emerging from the needs of nano and 3D fabrication require the development of laser processing strategies that can address critical issues such as machining resolution, processing speed and product quality. This dissertation concerns the development of novel laser processing strategies based on spatial, temporal and spectral control of light-matter interaction. In the spatial domain, beam shaping is employed in ultrafast laser micro-processing. Zero-order Bessel beam, generated by an axicon, is used for selective removal of the back contact layer of thin film solar cells. Bessel beam’s propagation-invariance property gives rise to an extension of focal range by orders of magnitude compared to Gaussian beam, greatly increasing process tolerance to surface unevenness and positioning error. Together with the axicon, a spatial light modulator is subsequently used to modify the phase of laser beam and generate superpositions of high-order Bessel beam with high energy efficiency. With the superposed beam, processing speed can be increased significantly, and collateral damage resulting from the ring structures in the zero-order Bessel beam can be greatly suppressed. In the temporal domain, it is demonstrated that ionization in dielectric materials can be controlled with a pair of ultraviolet and infrared pulses. With the assistance of the long-wavelength infrared pulse, nano-scale features are achieved using only a small fraction of threshold energy for the short-wavelength pulse. Computer simulation based on the rate equation model is conducted and found to be in good agreement with experimental results. This study paves the way for future adoption of short-wavelength laser sources, for example in the extreme ultraviolet range, for direct laser nano-fabrication with below-threshold pulse energy. In the spectral domain, a short-wavelength infrared laser is used to generate modification in the bulk of silicon wafers, in an attempt to develop 3D fabrication capabilities in semiconductors. Issues such as spherical aberration correction and examination procedure are addressed. Permanent modification is generated inside silicon by tightly focusing and continuously scanning the laser beam inside the samples, without introducing surface damage. The effect of laser pulse energy and polarization is also investigated. These results demonstrate the potential of controlling laser processing in multiple dimensions for manufacturing purposes, and point to a future when laser can be used as naturally and efficiently as mechanical tools used today, but is targeted at more challenging problems.
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Lavvafi, Hossein. "EFFECTS OF LASER MACHINING ON STRUCTURE AND FATIGUE OF 316LVM BIOMEDICAL WIRES." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1352743353.
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Holmberg, Patrik. "Laser processing of Silica based glass." Doctoral thesis, KTH, Laserfysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-173929.
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The main topic of this thesis work is photosensitivity and photo-structuring of optical fibers and bulk glass. Although research in the field of photosensitivity in glass and optical fibers has been ongoing for more than three decades, the underlying mechanisms are still not well understood. The objective was to gain a better understanding of the photo-response by studying photosensitivity from a thermodynamic perspective, as opposed to established research focusing on point defects and structural changes, and strain and stress in optical fibers. Optical fibers was mainly used for experimental studies for two reasons; first, photosensitivity in fibers is more pronounced and more elusive compared to its bulk counterpart, and secondly, fibers provide a simplified structure to study as they experimentally can be seen as one-dimensional.Initially, ablation experiments on bulk glass were performed using picosecond infrared pulses. With a design cross section of 40x40 μm, straight channels were fabricated on the top (facing incident light) and bottom side of the sample and the resulting geometries were analyzed. The results show a higher sensitivity to experimental parameters for bottom side ablation which was ascribed to material incubation effects. Moreover, on the top side, the resulting geometry has a V-shape, independent of experimental parameters, related to the numerical aperture of the focusing lens, which was ascribed to shadowing effects.After this work, the focus shifted towards optical fibers, UV-induced fiber Bragg gratings (FBGs) and thermal processing with conventional oven and with a CO2 laser as a source of radiant heat.First, a system for CO2 laser heating of optical fibers was constructed. For measuring the temperature of the processed fibers, a special type of FBG with high temperature stability, referred to as "Chemical Composition Grating" (CCG) was used. A thorough characterization and temperature calibration was performed and the results show the temperature dynamics with a temporal resolution of less than one millisecond. The temperature profile of the fiber and the laser beam intensity profile could be measured with a spatial resolution limited by the grating length and diameter of the fiber. Temperatures as high as ~ 1750 °C could be measured with corresponding heating and cooling rates of 10.500 K/s and 6.500 K/s.Subsequently, a thorough investigation of annealing and thermal regeneration of FBGs in standard telecommunication fibers was performed. The results show that thermal grating regeneration involves several mechanisms. For strong regeneration, an optimum annealing temperature near 900 C was found. Two different activation energies could be extracted from an Arrhenius of index modulation and Braggv iwavelength, having a crossing point also around 900 °C, indication a balance of two opposing mechanisms.Finally, the thermal dynamics and spectral evolution during formation of long period fiber gratings (LPGs) were investigated. The gratings were fabricated using the CO2 laser system by periodically grooving the fibers by thermal ablation. Transmission losses were reduced by carefully selecting the proper processing conditions. These parameters were identified by mapping groove depth and transmission loss to laser intensity and exposure time.Huvudtemana i denna avhandling är fotokänslighet och fotostrukturering av optiska fibrer och bulk glas. Trots att forskning inom fotokänslighet i glas och optiska fibrer har pågått under mer än tre decennier är de bakomliggande mekanismerna ännu inte klarlagda. Syftet var att få en bättre förståelse för fotoresponsen genom att studera fotokäsligheten ur ett termodynamiskt perspektiv, i motsats till etablerad forskning med fokus på punktdefekter och strukturförändringar, samt mekaniska spännings effekter i optiska fibrer. Optiska fibrer användes för flertalet av de experimentella studierna av två skäl; för det första är fotokänsligheten i fibrer större och dessutom vet man mindre om bakomliggande mekanismer jämfört med motsvarande bulk glas, och för det andra kan fibrer vara enklare att studera eftersom de experimentellt kan ses som en endimensionell struktur.Inledningsvis utfördes ablaherings experiment på bulk glas med en infraröd laser med pikosekund pulser. Raka kanaler med ett designtvärsnitt på 40x40 μm tillverkades på ovansidan (mot infallande ljus) och bottensidan av provet och de resulterande geometrierna analyserades. Resultaten visar en högre känslighet för variationer i experimentella parametrar vid ablahering på undersidan vilket kan förklaras av inkubations effekter i materialet. Dessutom är den resulterande geometrin på ovansidan V-formad, oavsett experimentella parametrar, vilket kunde relateras till den numeriska aperturen hos den fokuserande linsen, vilket förklaras av skuggningseffekter.Efter detta arbete flyttades fokus mot optiska fibrer, UV inducerade fiber Bragg gitter (FBG), och termisk bearbetning med konventionell ugn samt även med en CO2-laser som källa för strålningsvärme.Först konstruerades ett system för CO2-laservärmning av fibrer. För mätning av temperaturen hos bearbetade fibrer användes en speciell sorts FBG med hög temperaturstabilitet, kallade ”Chemical Composition Gratings” (CCG). En grundlig karaktärisering och temperaturkalibrering utfördes och temperaturdynamiken mättes med en tidsupplösning på under en millisekund. Temperaturprofilen i fibern, och laserns strålprofil, kunde mätas med en spatiell upplösning begränsad av gitterlängden och fiberns diameter. Temperaturer upp till ~1750 °C, vilket är högre än mjukpunktstemperaturen, kunde mätas med korresponderande uppvärmnings- och avsvalningshastighet på 10.500 K/s och 6.500 K/s.Därefter gjordes en omfattande undersökning av värmebearbetning och termisk regenerering av FBG:er i telekomfiber. Resultaten visar att termisk gitter-regenerering aktiveras av flera olika mekanismer. Värmebearbetning vid en temperatur omkring 900 °C resulterade i starka gitter efter en regenerering vid en temperatur på 1100 °C. Två olika aktiveringsenergier kunde extraheras från en Arrhenius plot avseende brytningsindexmodulation och Braggvåglängd, med en skärningspunkt tillika runt 900 °C, vilket indikerar en avvägning mellan två motverkande mekanismer vid denna temperatur.Slutligen undersöktes temperaturdynamiken och de spektrala egenskaperna under tillverkning av långperiodiga fibergitter (LPG). Gittren tillverkades med CO2-vi iilasersystemet genom att skapa en periodisk urgröpning medelst termisk ablahering. Transmissionsförluster kunde reduceras med noggrant valda processparametrar. Dessa parametrar identifierades genom mätningar av ablaherat djup och transmissionsförlust som funktion av laserintensitet och exponeringstid.
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Kumar, Mukund. "Laser assisted micro milling of hard materials." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41213.
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This thesis presents an investigation of novel laser assisted micromachining processes that addresses the limitations of micromachining of hard-to-machine materials. Two different laser assisted approaches are used to machine hard metals and high strength ceramics. For hard metals, the basic approach involves localized thermal softening of the workpiece material by focusing a solid-state continuous wave near infra-red laser beam in front of the micro milling tool (end mills of 0.1 to 0.5 mm diameter). By suitably controlling the laser power, spot size and scan speed, it is possible to produce a sufficiently large reduction in the flow strength of the work material and consequently the cutting forces and tool deflections. A force model is developed to predict the cutting forces in Laser Assisted Micro Milling (LAMM) of hard metals. For high strength ceramics, the approach involves use of a two step process. In the first step, thermal cracks are generated in a confined volume by the steep thermal gradients generated by laser irradiation of the workpiece. In the second step, the weakened region is removed by a micro grinding tool. The characterization and modeling of the process serve as bases for users of the two approaches to select optimal process parameters.
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VIDAL, JOSE T. "Desenvolvimento de um sistema opto-mecanico para micro usinagem com laser de fentossegundos." reponame:Repositório Institucional do IPEN, 2010. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9563.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Carvalho, Marta Regina Delle Donne 1962. "Análise comparativa de meios de preparação do substrato para ferramentas de torneamento revestidas pelo processo PVD." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263007.
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Orientador: Anselmo Eduardo DinizDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Abstract: The abstract is available with the full electronic document
Mestrado
Materiais e Processos de Fabricação
Mestra em Engenharia Mecânica
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Shen, Xinwei. "Numerical modeling and experimental investigation of laser-assisted machining of silicon nitride ceramics." Diss., Kansas State University, 2010. http://hdl.handle.net/2097/6645.
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Doctor of PhilosophyDepartment of Industrial & Manufacturing Systems Engineering
Shuting Lei
Laser-assisted machining (LAM) is a promising non-conventional machining technique for advanced ceramics. However, the fundamental machining mechanism which governs the LAM process is not well understood so far. Hence, the main objective of this study is to explore the machining mechanism and provide guidance for future LAM operations. In this study, laser-assisted milling (LAMill) of silicon nitride ceramics is focused. Experimental experience reveals that workpiece temperature in LAM of silicon nitride ceramics determines the surface quality of the machined workpiece. Thus, in order to know the thermal features of the workpiece in LAM, the laser-silicon nitride interaction mechanism is investigated via heating experiments. The trends of temperature affected by the key parameters (laser power, laser beam diameter, feed rate, and preheat time) are obtained through a parametric study. Experimental results show that high operating temperature leads to low cutting force, good surface finish, small edge chipping, and low residual stress. The temperature range for brittle-to-ductile transition should be avoided due to the rapid increase of fracture toughness. In order to know the temperature distribution at the cutting zone in the workpiece, a transient three-dimensional thermal model is developed using finite element analysis (FEA) and validated through experiments. Heat generation associated with machining is considered and demonstrated to have little impact on LAM. The model indicates that laser power is one critical parameter for successful operation of LAM. Feed and cutting speed can indirectly affect the operating temperatures. Furthermore, a machining model is established with the distinct element method (or discrete element method, DEM) to simulate the dynamic process of LAM. In the microstructural modeling of a β-type silicon nitride ceramic, clusters are used to simulate the rod-like grains of the silicon nitride ceramic and parallel bonds act as the intergranular glass phase between grains. The resulting temperature-dependent synthetic materials for LAM are calibrated through the numerical compression, bending and fracture toughness tests. The machining model is also validated through experiments in terms of cutting forces, chip size and depth of subsurface damage.
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Bricchi, Erica. "Femtosecond laser micro-machining and consequent self-assembled nano-structures in transparent materials." Thesis, University of Southampton, 2005. https://eprints.soton.ac.uk/30234/.
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In this thesis we have reported novel developments in the field of femtosecond laser micro-machining within the bulk of transparent materials. Thanks to its unique properties, the femtosecond laser writing technique offers the potential for realizing three-dimensional multi-component photonic devices, fabricated in a single step and in a variety of transparent materials. When we began to research in this field, there had been no studies conducted on the ability of femtosecond lasers to fabricate diffractive optical components in the bulk of a dielectric material. These are necessary components for the realization of monolithic optical devices. Our work led to the first demonstration of femtosecond directly written diffractive optic devices (Fresnel zone plates) embedded in a silica substrate. Both the focusing properties and efficiencies of the devices compared well with the theoretical values.
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Yahyavi, Zanjani Matin, Henning Zeidler, André Martin, and Andreas Schubert. "Application of Laser Scanning as a Pre-machining metrology technique in Jet-ECM." Universitätsbibliothek Chemnitz, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-227104.
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In Electrochemical Machining (ECM), where the material removal takes place based on the anodic dissolution of the workpiece material, the working distance is one of the most important parameters. Especially in Jet Electrochemical Machining (Jet-ECM), where a micro nozzle is moved over the initial surface of the workpiece in order to apply an electrolytic free jet to produce the desired shapes, the distance between the nozzle and the workpiece becomes even more important. On the one hand a small working distance is aspired to achieve high current densities resulting in a high efficiency of the process. On the other hand the working distance needs to be large enough to avoid damages on the micro nozzle caused by electrical discharges or mechanical contact. Hence, the adjustment of the working gap is essential to realize a precise, effective and secure Jet-ECM process.
The control of the gap size is done based on the data gathered before machining by surface measurement. Until now, the initial surface has been detected by electrostatic probing through moving the nozzle stepwise to the work piece surface and detect the voltage drop between the nozzle and the work piece. With this strategy, only a limited number of points can be detected within adequate time. Hence, in most cases only three points of the initial surface are detected in order to adjust the working distance according to the planar inclination of the workpiece. The coordinates of the three detected points are used to calculate the normal vector of the initial surface. In recent studies, another strategy was analysed, which is realized by dividing the surface into smaller areas and respectively calculating the normal vector of each area in order to obtain more accurate data of the initial surface. A further strategy is to use probing along the machining path of the tool and to gather the coordinates of a number of points along the path.
The above mentioned methods usually do not ensure the precise control of the gap size especially for the surfaces with complex geometry with locally confined convex and concave shapes and are highly affected by the size of the probe. In this study, the application of a laser scanner is investigated for the measurement of the workpiece surface before machining to gather the required data for the adjustment of the working distance during Jet-EC machining of complicated surfaces.
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Vora, Hitesh D. "Integrated Computational and Experimental Approach to Control Physical Texture During Laser Machining of Structural Ceramics." Thesis, University of North Texas, 2013. https://digital.library.unt.edu/ark:/67531/metadc407758/.
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The high energy lasers are emerging as an innovative material processing tool to effectively fabricate complex shapes on the hard and brittle structural ceramics, which previously had been near impossible to be machined effectively using various conventional machining techniques. In addition, the in-situ measurement of the thermo-physical properties in the severe laser machining conditions (high temperature, short time duration, and small interaction volume) is an extremely difficult task. As a consequence, it is extremely challenging to investigate the evolution of surface topography through experimental analyses. To address this issue, an integrated experimental and computational (multistep and multiphysics based finite-element modeling) approach was employed to understand the influence of laser processing parameters to effectively control the various thermo-physical effects (recoil pressure, Marangoni convection, and surface tension) during transient physical processes (melting, vaporization) for controlled surface topography (surface finish). The results indicated that the material lost due to evaporation causes an increase in crater depth of machined cavity, whereas liquid expulsion created by the recoil pressure increases the material pileup height around the lip of machined cavity, the major attributes of surface topography (roughness). Also, it was found that the surface roughness increased with increase in laser energy density and pulse rate (from 10 to 50Hz), and with the decrease in distance between two pulses (from 0.6 to 0.1mm) or the increase in lateral and transverse overlap (0, 17, 33, 50, 67, and 83%). The results of the computational model are also validated by experimental observations with reasonably close agreement.
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Randeree, Kasim. "Development of an integrated laser - based tool inspection system for a CNC machining centre." Thesis, University of Hull, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301631.
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Mahmood, Khalid. "An investigation into laser deposition of machining chips and characteristics of the final clad." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/an-investigation-into-laser-deposition-of-machining-chips-and-characteristics-of-the-final-clad(45daf674-4f3f-487b-b25c-14fab168b5d0).html.
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Laser metal deposition is an additive manufacturing technique to build fully dense structures with a strong metallurgical bonding with the underlying material. Spherical gas-atomised metal powders are principally used as build material which is a costly option and restricts its application on a wide scale. On the other hand, nonspherical particles produced by machining are much cheaper to produce and readily available as waste swarf which should be recycled. The use of machined particles as a viable form of build material for laser direct metal deposition has not been explored previously and is the subject of the investigations reported in this thesis. In the first work, samples of carbon steel machining swarf in three size ranges were laser deposited to build thin walls. The produced walls exhibited fine martensitic microstructure with minimal porosity. As general trends, individual deposition tracks were found to be lower, and wider with an increase of particle size. 50% reduction in hardness was observed when using coarser particle size. This work was extended so as to build U-shaped structures with variable laser power in contrast to the previous work which was done with one set of processing parameter values. The microstructure observed was similar to that of the previous work. However, hardness has found to increase with decrease in laser power. After successful deposition and encouraging results from the process, machining swarf of Inconel 617 was used to produce corrosion resistant layers on a mild steel substrate. A Design of Experiment methodology was used to analyse the relationship between the processing parameters and the coated layer characteristics. The layer thickness and hardness were found to increase with the mass feed rate whilst an increase in laser power produced the opposite result. All layers had a predominantly dendritic microstructure and displayed remarkably higher corrosion resistance than the mild steel sample. The work was expanded to investigate the surface characteristics and corrosion resistance in a harsh corrosive environment, using different pH brine solutions. In this investigation, four layers were produced with two laser power and mass feed rate values. Accounting for all measurements, Inconel 617 swarf built layers provided very good corrosion protection and confirmed the viability of using this method as a low-cost corrosion protection for both mild and harsh environments. Since the investigations authored above were confined to swarf alone, the final chapter examines the comparison of stainless steel 316L thin wall structures produced with swarf and gas-atomised powder using similar processing conditions. The build materials performed similarly, but walls made from swarf were slightly shorter with a coarser microstructure and had poorer corrosion resistance than the powder equivalents.The results of these investigations confirm the feasibility of machining swarf as an alternative viable option. However, further research will help to explore its full potential.
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Kalyanasundaram, Dinesh. "Mechanics guided design of hybrid laser/waterjet system for machining hard and brittle materials." [Ames, Iowa : Iowa State University], 2009.
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Ilyas, Ismet Priana. "Production of plastic injection moulding tools using selective laser sintering and high speed machining." Thesis, University of Leeds, 2007. http://etheses.whiterose.ac.uk/4048/.
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Global manufacturing trend and competition challenge every industry to seek new manufacturing methods to improve their business processes and speed up the product development cycle [Conolly, 2004a and Knights, 2001]. Among the candidates, layer manufacturing (LM) technologies appear to be a potential solution [Plam, 2002, and Grimm, 2004]. Recent LM technologies have led to a demanding application for developing production tools to manufacture parts, known as rapid tooling (RT). Selective laser sintering (SLS) is one of the leading LM systems available today in RT to manufacture injection mould (core/cavity) inserts [Kruth, 1998, Chua, 1999, Dormal, 1999, and Grenda, 2005]. However, the current capabilities of the SLS in producing metal parts have not yet fulfil the requirements of the injection mould inserts, especially in dimensional accuracy and surface finish quality [Francis, 2002 and Dalgamo, 2001 a]. The aim of this research is to use indirect SLS and high speed machining (HSM) in developing production-quality plastic injection moulding (core/cavity) inserts. The idea is that the indirect SLS process is utilised to build a near-net-shape inserts, while HSM is then utilised to finish the inserts to production specifications. Benchmark studies have been carried out to characterise the capabilities of both SLS and HSM with reference to the typical requirements of injection mould inserts. Utilising the study results, new developments of the mould inserts have been implemented on three major industrial case studies. Their performances have been evaluated and measured by comparing them with its respective original inserts. Furthermore, a set of design rules has been derived from best practices of the case studies, and have been validated by developing a new design for each case studies inserts. The results have demonstrated that the indirect SLS process has a capability III manufacturing a near-net shape of the insert which requires further related finishing to achieve final production specifications. The insert performances in some case studies have indicated significant improvements in process productivity and energy consumption as well as economic benefits to using the inserts. Regarding the significant considerations in realising the design, a recommendation on further strategic design rules and manufacturing process are highlighted so that the development of the insert using the selected approach can be more effective and efficient. Moreover, a utilisation of computer analysis software and further durability trial is also highlighted in order to predict and evaluate the optimum overall performance.
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Huang, Hsin-Yi, and 黃欣怡. "Laser Micro-machining on Engeering Materials." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/65914911817157213187.
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碩士國立臺灣大學
機械工程學研究所
94
The 21st century is high-tech generation with products containing various kinds of micro-structures and micro-components. With the development of associated manufacturing technology, the industry needs, in many occasions, to carry out the processing of micro-structure on brittle materials. The use of chemistry-etching has the advantage on high accuracy, but its process is complex and has low efficiency. Now the trend is to attempt use of the laser machining to replace the conventional ways. The material removal by laser micro-machining have two kinds: photothermal and photochemical mechanisms. The processing via photochemical mechanism moves materials in a way that photons break the chemical bonds of the material directly without the high temperatures accompanied, and the machining accuracy will be much higher than that via photothermal mechanism. The femtosecond laser has a characteristic of extremely short pulse, whose working mechanism falls to photochemical category. The research on femtosecond laser applications has not been widely carried out at present, but showing great potentiality. In order to grasp its characteristics, this research was planned on the fundamental investigation and comparison was made with the Nd:YVO4 laser resualts which widely applied in industry.
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Chiu, Yi-Hsin, and 邱義信. "Resonant Optical Biosensor with Laser Machining." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/26819674146969750218.
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碩士國立陽明大學
醫學工程研究所
101
Fiber-optic biosensor plays an important role in the development of biosensors and provides the following advantages: miniaturized, real-time detection, and high sensitivity of fluorescence techniques. By all the advantages and applying fiber-type resonator can enhance the strength of the evanescent waves, which achieve to enhance fluorescence signal. In this study, fiber-type resonator is demonstrated using a pair of optical reflectors attached to both ends of the optical fiber. In this design, we are using a pair of optical reflectors attached to both ends of optical fiber to make the fiber-type resonator and drilled a hole about 30 um in it by a laser drilling system. The excitation light is coupled into the optical fiber through a small hole in the front reflector and reflected many times to excite the AF 488 (fluorescent molecule) labeled IgG on the surface of the optical fiber between the paired reflectors. In this study, the laser drilling system can provide a precise results and the reaction area can be made by CO2 laser. It also can be meaningful for quantitative analysis. Therefore, the results show that the system of limit of detection is 10ng/ml. Fluorescent amplification ratio can achieve around 800% and also increase the sensitivity of Signal-to-noise ratio (SNR). It also provides a low energy and low cost in resonant optical biosensor.
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Hung, Chien-Chih, and 洪健智. "EDM and Laser Machining of Ti3SiC2." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/44003834926822466195.
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碩士義守大學
機械與自動化工程學系碩士班
96
Titanium Silicon Carbide (Ti3SiC2) exhibits a unique combination of mechanical properties that have been studied intensively for more than one decade. The crystal structure is comprised of hexagonal nets of Si atoms separated by three layers of nearly close-packed layers of Ti that accommodate C atoms in the octahedral sites between them. It is a relatively light (4.5 g/cm3) solid that is oxidation resistant and stable up to at least 1700℃ in inert atmospheres and vacuum. It has excellent machinability and it is not susceptible to thermal shock. The low ratio of hardness/Young’s modulus suggests the mechanical behavior is similar to that of ductile metals. This paper presents a detailed investigation of the typical EDM material removal mechanisms of Ti3SiC2. This experiment has been carried out on the influence of different factors like pulse time, duty cycle, open-circuit voltage… on the die-sinking EDM. It is evaluated the feasibility of die material used in room temperature and high temperatures
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Li, Ming-Feng, and 李銘峯. "Fabrication of Micro Dye Lasers Using Laser Machining Technology and UV Lithography." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/tj8n8n.
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碩士國立嘉義大學
光電暨固態電子研究所
97
In recent years the research in micro dye lasers develops vigorously for the capability of being integrated with the light source based sensor chip to form a lab-on-a-chip micro-opto-electro-mechanical system. Especially the micro dye laser which can produce single-mode output attracts much attention for the sake of being suitable for the application in the high precision interferometric sensor. Nowadays, there are various manners to fabricate micro dye lasers such as laser machining technology, UV lithography, E-Beam lithography and micro-nanoimprint technology. The difference in manufacture methods will affect the precision of the resonator structure, and the optical characteristics and quality of the laser output. In this research, we first utilize the femtosecond laser machining technology to fabricate the resonator structure of the microfluidic micro dye laser directly on the surface of a glass plate. Besides exploring the features of femtosecond laser machining, we also utilize the UV lithography to fabricate solid-state micro dye lasers. We have compared the spectral characteristics of the dye laser outputs, investigated the life time of the dye laser gain medium, and measured the transmission spectrum of the micro resonator structure.
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Li, Chun-hao, and 李俊豪. "Study of solid-state laser source implementation and laser beam machining optimization." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/96922914758944562939.
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博士國立臺灣科技大學
自動化及控制研究所
97
This study focuses on implementation of two wavelengths Q-switched diode-pumped solid-state laser (DPSSL) source and multi-objective optimization for two kinds of laser beam machining (LBM) using grey relational analysis (GRA). Many laser machining processes need a 1064 nm or 532 nm laser source to obtain suitable quality for satisfying different requirements. Firstly, this work proposes a single laser source module with a Q-switched diode-pumped Nd:YAG laser that can be quickly switched between 1064 or 532 nm wavelength generation, and can be used for multiple processes in industrial applications for space and cost savings. By using an intra-cavity aperture of 1.2 mm diameter with 5 mm length, and using high linear and high repetition accuracy slide stage to load both the back cavity modules of 1064/532nm wavelengths, the experimental results of the 1064/532 nm module demonstrate that a high laser beam TEM00 quality is successfully obtained. The measured average powers and durations of the 1064/532 nm laser source module were similar under operating repetition rates from 10 kHz~35 kHz. Secondly, the Q-switched DPSSL and grey relational analysis (GRA) are used for machining applications which include (1) optimization of laser cutting for flash memory modules with special shapes by using GRA; and (2) optimization of laser scribing isolation for short-circuit rings of TFT-LCDs by using GRA. When satisfying the requirement for manufacturing speed, the GRA multiple characteristics of laser cutting process for flash memory with special shapes were the smaller-the-better for the roughness and the heat effect zone (HAZ). The most important control factor is the Q-switched repetition rate from the analytical results of 8 experiments. When the manufacturing speed is fixed, the GRA multiple characteristics of laser scribing isolation process for LCD short-rings were the smaller-the-better for the widths of groove and hillock, the most important control factor is the aperture pinhole diameter for single mode of laser quality from the analytical results of 8 experiments. Analysis of the grey relational grade indicates parameter significance and the optimal parameter combination for the LBM can be identified to verify the performance by extra-confirmation experiments. Therefore, the integration of LBM technology and the GRA method can be effectively applied on new processing applications.
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Chiu, Bo-Ming, and 邱博明. "Intelligent Laser Power and Machining Stage Motion Control." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/pvpkbu.
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碩士國立臺北科技大學
自動化科技研究所
99
This paper for “Intelligent Laser Power and Machining Stage Motion Control” subjects to research. Laser machining is widely used in many industry applications, such as medical, machinery, military. Both the laser output power and performance of machining motion stage will affect the quality of laser machining. The laser system is a nonlinear system due to its complexity and easily affected by environment conditions. This paper uses intelligent self-tuning fuzzy PI controller to stabilize the laser power control. The advantages of using FRE for nonlinear controlled systems can be controlled to produce proper input, and obtain the ideal response. In addition, we adopt global sliding mode control with the PID-like neural network (GSMCNN) estimator in linear motor control. Global sliding mode controller is a robust control architecture that can guarantee the system’s responses are controlled in the sliding layer. The elimination of the traditional sliding mode controller is approaching fast switching, the system can achieve the desired control response and position. PID-like neural network estimator replaces the traditional switching function and saturation function. By neural network going to dynamic learning, we can overcome the friction can eliminate the chattering phenomenon of switching function. Finally, after comparing GSMCNN with traditional controller, we can find that GSMCNN can achieve the best robustness and control performance.
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Yeh, Zhi-Chang, and 葉智全. "Excimer Laser Micro-Machining of ObliqueSurface and Grooves." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/27607023918989908839.
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碩士國立成功大學
機械工程學系碩博士班
91
In this work, the ablation of polymeric materials (PI and PMMA) exposed to an oblique laser beam and the micro-machining of V-grooves and high-aspect-ratio holes in polymetric materials using KrF excimer laser radiation are considered. Modeling and measurement methods for the oblique ablation of polymeric materials are developed. The modeling includes the absorption of laser light by chromophores, energy conversion and material ablation. The experiment includes the measurement of the light intensity through the ablation plume and the ablation depth and the observation of the machining properties of the polymers. The simulation and the measurement results are compared to examine the model. The comparison shows that the modeling is valid. The ablation rate decreases with the increase of the incident angle, but increase with the increase of the fluence. Next, we develop a micro-machining method based on the defocus of the laser beam. The effects of this method on the micro-drilling and the micro-machining of V-grooves are investigated. The defocus of the laser beam changes the local distribution of the light over the micro-machined surface. When the degree of the defocus increases, the beam size increases and its intensity decreases. Thus, the size of the opening of the hole increases. When the distance between the focus plane and the polymer surface is in the range 150~350 m µ , a few hundreds pulses can generate a V-groove. The width of the groove increases with the increase of the distance.
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Yolchuyeva, Ayisha. "Laser machining steel for moulds: a case study." Master's thesis, 2016. http://hdl.handle.net/10400.8/2138.
Full textAbstract:
Laser beam machining is a non-traditional subtractive manufacturing process, a form of
machining, in which a laser is directed towards the work piece for machining. This process uses
thermal energy to remove material from metallic or non-metallic surfaces. The laser is focused
onto the surface to be worked and the thermal energy of the laser is transferred to the surface,
heating and melting or vaporizing the material. Laser beam machining is best suited for brittle
materials with low conductivity, but can be used on most materials. The role of the technical
equipment in laser milling is to perform a controllable action of the laser radiation on the
material to be treated. The laser is the main unit of the equipment and it is characteristics
determine to great extent the qualitative and quantitative parameters of the technological
treatments.
In this work, I had to study the laser milling process parameter selection for process
planning operations from start to finish. It was important to have an understanding about laser
milling and laser processing parameters for different materials. As a result from the laser milling,
the surface finish will have different surface properties such as, surface hardness, surface
roughness, friction and tribology etc.. During the process, I gained knowledge about the
historical and conceptual framework of laser milling, the different parameters of a laser milling
and how the laser milling parameters influence the surface properties of the machined parts.
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Samant, Anoop. "Laser Machining of Structural Ceramics: Computational and Experimental Analysis." 2009. http://trace.tennessee.edu/utk_graddiss/99.
Full textAbstract:
Outstanding mechanical and physical properties like high thermal resistance, high hardness and chemical stability have encouraged use of structural ceramics in several applications. The brittle and hard nature of these ceramics makes them difficult to machine using conventional techniques and damage caused to the surface while machining affects efficiency of components. Laser machining has recently emerged as a potential technique for attaining high material removal rates. Major focus of this work is to understand the material removal mechanisms during laser machining of structural ceramics such as alumina (Al2O3), silicon nitride (Si3N4), silicon carbide (SiC) and magnesia (MgO). A 1.06 μm wavelength pulsed Nd:YAG laser was used for machining cavities of variable dimensions in these ceramics and an ab-initio computational model was developed to correlate attributes of machined cavities with laser processing conditions.
Material removal in Al2O3, Si3N4 and SiC takes place by a combination of melting, dissociation and evaporation while dissociation followed by evaporation is responsible for material removal in MgO. Temperature measurement at high temperatures being difficult, thermocouples were used to measure temperatures in the low temperature regime (700- 1150K). A thermal model was then iterated to obtain trends in absorptivity variation below phase transition temperature for these ceramics. Following this, measured machined depths were used as a benchmark to predict absorptivity transitions at higher temperatures (> 1150K) using the developed thermal model. For temperatures below phase transition, due to intraband absorption, the absorptivity decreases with increase in temperature until the surface temperature reaches the melting point in case of Al2O3, Si3N4 and SiC and the vaporization temperature in case of MgO. The absorptivity then continues to follow increasing trend with increasing temperature due to physical entrapment of laser beam in the cavity evolved during machining of certain depth in the ceramic. Rate of machining was predicted in terms of material removed per unit time and it increased with increase in heating rate.
Such a composite study based on comput ational and experimental analysis would enable advance predictions of laser processing conditions required to machine cavities of desired dimensions and thus assist in controlling the laser machining process more proficiently.
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Yih-Hung, Chen, and 陳誼鴻. "Excimer Laser Micro-machining of Polymer and Semiconductor Materials." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/90711112572787371377.
Full textAbstract:
碩士中正理工學院
兵器系統工程研究所
87
ABSTRACT Owing to their high energy density and efficiency, CO2 and Nd-YAG laser are widely used for surface treating and cutting of materials. However, unwanted flow of molten materials due to thermal energy and poor surface and edge quality are normally the results when CO2 and Nd-YAG lasers were used for machining of polymer or ceramic materials. In comparison to the CO2 and Nd-YAG lasers, excimer lasers have relatively shorter wavelength which means that better optical resolution and machining accuracy can be achieved by using excimer lasers. The high energy density and short pulses of excimer lasers can instantly ionize/vaporize materials (i.e. laser ablation) and leave clean, well defined edges. The thermal damage in the surrounding materials can also be significantly reduced. The excimer laser is becoming one of the most powerful facilities for the high precision machining of materials. KrF(248nm) excimer laser was used in the research for the ablation of PC, PI polymer materials and a silicon single crystal. The results showed that photochemical and photo-thermal are the dominant material removal mechanism involved in excimer laser ablation of polymer materials and the silicon single crystal respectively. The etched depth of PI and PC increases with the repetition rate, fluence, pulse duration and pulse number. However, the etch rate reduced sharply as the etched hole gets deeper; for it gets harder for the generated plasma to be dispersed. Keywords：excimer laser, laser ablation
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Lin, Yan-Wei, and 林彥瑋. "Research on Property of Laser Machining on Acrylic Materials." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/38c93m.
Full textAbstract:
碩士國立虎尾科技大學
創意工程與精密科技研究所
99
This thesis mainly focuses on discussing the impact of machining parameters on machining quality when acrylic materials are machined by laser. At present, there are no accurate machining parameters of acrylic materials machined by laser for reference on the market, therefore, this thesis aims at setting up optimized parameters of acrylic materials. This thesis adopts Taguchi’s orthogonal arrays to allocate experimental factors of and set up parameters of acrylic materials machined by laser and empirical formulas of target properties. It’s expected to substantially improve surface quality and machining efficiency of acrylic materials and reduce production cost by introducing optimized parameters. In addition, it’s hoped to improve traditional complex machining process by making using of machining characteristics of laser in order to meet the trend of green manufacturing of current industry. The system of laser machining equipment takes HELIX (50W) and mini (30W) of CO2 laser machining equipment as experimental machines. Factors that impact quality of laser machining are resolution, engraving speed, power intensity, engraving frequency, etc. and surface profilers are used to test surface roughness of finished products and calculate specific values to compare data of quality characteristics. Calculate and record parameters of laser machining and make statistical analysis of calculated data. Then observe surface structure of test pieces through microscopes and find out quality pieces and optimized pieces. Through practical machining on those acrylic materials, we can work out results of Taguchi optimization. If the experiment is confirmed to be correct, then it can be used as reference for future study among academic and industrial circles. Key words: laser machining, acryl, Taguchi optimization
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Ji, Jheng-Hong, and 紀政宏. "Research on Property of Laser Machining on Metal Materials." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/k6uuwv.
Full textAbstract:
碩士國立虎尾科技大學
機械與電腦輔助工程系碩士班
103
In the present study, the researchers used a laser engraver to process different metal materials (stainless steel, iron, aluminum, brass, and copper) to elucidate the influences that various processing parameters have on processing quality. These parameters include engraving speed, power intensity, impulse frequency, and number of engravings. The more favorable parameters for metal processing can serve as a reference for improving processing efficiency and reducing production costs. The researchers adopted the factors of a Taguchi Orthogonal Table for testing to independently determine minimum coarseness and maximum removal rate (MRR). The results obtained in the present study were then used to calculate the S/N ratio of the various specimens. By analyzing the S/N ratios, response tables, and response charts, as well as performing an ANOVA, the researchers determined contribution and the degree of influence that the various factors had on quality. Among the different metal types, surface MRR manifested a positive correlation with power intensity. At a laser resolution of over 500 DPI, surface coarseness increased concurrently with an increase in laser resolution. The copper and brass specimens were highly reflective and were favorable heat conductors. Thus, their dampened light absorption capability rendered the surfaces of these specimens more resistant to melting. Moreover, the depth of engravings increased concurrently with a reduction in engraving speed.
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Lin, Chung-Wei, and 林忠緯. "A study of Laser Micro-Machining on the Silicon Wafer." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/00266999452027389378.
Full textAbstract:
碩士國立中正大學
機械工程所
95
Wafer means the semiconductor integrated circuit to need material. Taiwan takes the place of one of the works important country in silicon wafer for the world at present, so there is its necessity in the technology of probing into silicon wafer processing. Silicon wafer is a fragility material, traditional mechanical processing method is limited to the diameter of cutter that the corners and small characteristics can’t be processed. To focus the laser spot size very small can overcome above disadvantages. Laser processing that photothermal material removing and photochemical ablation will make heat affect zone and recasting that influence the quality of processing. In this research, utilize Pico-second laser, UV laser and Nd : YAG laser to micro-machining on the silicon wafer, adjusts the laser parameters and additional assist equipment to improve and observe its processing result and confer with different laser’s processing mechanism and correlate with each other. The planning of the micro-structure, for the micro-structure of this kind of saw tooth structure of probe card that the industry uses now. Using different lasers to process silicon wafer, adjustment of parameter receives better processing results, how to understand processing characteristic of three kinds of lasers and find to correlations for each other is key point in this research. Among this thesis, we utilize laser to process a micro-structure of good quality successfully. According to process results, we understand the quality of micro-structure to correlate with pulse width, wavelength absorption depth each other. To Supply a basis to select a laser while processing different materials in the future. Key word：silicon wafer、Pico-second laser、UV laser、Nd：YAG laser、 Micro-machining、pulse width、wavelength absorption depth
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Cheng-HsiangLin and 林正祥. "Study of Femto/nano-second Laser Micro/nano-scale Machining." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/40825233060905913882.
Full textAbstract:
博士國立成功大學
工程科學系碩博士班
98
Laser micromachining has been widely applied not only for industry but also for research demands. Nanosecond pulse laser systems are popular used in industry due to the high production throughput and low operation cost. However, the significant drawback of the laser systems is difficult to machine dielectric materials due to low absorptivity in wavelength range from visible to near infrared. Currently, the drawback has been addressed by femtosecond pulse lasers via multiphoton absorption induced by extremely high peak power. The femtosecond laser systems have opened a new window in laser micromachining. In this thesis, pulse laser micromachining technologies including nanosecond laser micromachining as well as femtosecond laser micromachining were investigated and focused on improving the machining accuracy and throughput and developing sensors. A depth measuring technique for laser hole drilling was developed via the confocal principle to overcome the issue of the unknown machining depth during the laser machining because the machining depth is multiparameter-dependent factors such as laser fluence, pulse duration, wavelength, etc. The developed depth measuring system was successfully integrated into a nanosecond micromachining system with a resolution of 0.5 μm. Furthermore, employing the rapid thermal delivering characteristic of nanosecond laser pulses, a laser-nanostructured substrate with dense and high uniformity gold nanoparticles on the surface was fabricated by the nanosecond laser annealing of a gold thin film coated on silicon wafer. The laser machining substrate is utilized for surface-enhanced Raman scattering (SERS). An enhancement factor of 105 by comparing the normal Raman and SERS signals was demonstrated for the Rhodamine 6G sample at 632.8 nm wavelength excitation. In the femtosecond machining, the machining with focus shaping was utilized to fabricate 3D microlens arrays including cylindrical lens and spherical lens at horizontal and vertical arrangements in photosensitive glass. Focusing quality and imaging testing were conducted to examine the performances of the fabricated microlens arrays. In the same photosensitive glass material, an optical fiber assisted Fabry-Perot interferometer embedded in a glass chip as a refractive index sensor for liquid samples was also developed. By machining silicon wafer substrates in silver nitrate solution with the femtosecond lasers, high sensitivity SERS substrates were produced and the enhancement factor was calculated as 109. Finally, a femto/nano-second dual-beam micromachining system has been developed and benefits the ablation efficiency on dielectric materials which are usually difficult to machine by other types of lasers such as continuous-wave laser and single nanosecond pulse laser.
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Wang, C. T., and 王政泰. "Construction and study on the technique of laser-assisted-machining." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/09156135516823125458.
Full textAbstract:
碩士國立中正大學
機械系
92
ABSTRACT This study focuses on the construction and development of the technique-- Laser-assisted-machining, LAM. It contains that verifies the feasibility of LAM and creates necessary theory. Laser-assisted-machining is a developing technique of processing hard-to-cutting materials. The main concept of machining utilizes the phenomena which a solid will be softened as located in a high temperature condition. While the laser ray is focused on the surface of workpiece, a tiny local part where is irradiated by laser will be heated to a high temperature region. At this instant, removing the heated and softened part of material by tool is more easily than conventional ways that the tool wear could be effectively reduced. Therefore, developing LAM technique makes the machining cost down. It’s hard-to-cutting metal and brittle ceramics that LAM skill wishes to cut, such as supper alloy--Inconel-718 or ceramic--Al2O3. Overseas, there are preliminary experimental results on LAM technique, but not any literature could be found domestically. Therefore, this study hopes to develop our own LAM technique in Taiwan. A finite element model has been created to compute temperature rising on workpiece due to laser irradiation and an orthogonal cutting model to estimate cutting force. The primary experimental result is able to ensure the feasibility of LAM on cutting ceramics. We hope this cutting technique can expand the method of machining ceramic beyond conventional grinding way. By LAM, ceramics with brittle and hard characteristic could be machined by milling or turning ways. The rise of processing efficiency and reduction of tool wear are the major benefit.
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傅筠強. "Molecular Dynamics study of Laser micro-machining of metal film." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/45173565444635585065.
Full text