Dissertations / Theses on the topic 'Laser manufacturing'
To see the other types of publications on this topic, follow the link: Laser manufacturing.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Laser manufacturing.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Mikler, Calvin. "Laser Additive Manufacturing of Magnetic Materials." Thesis, University of North Texas, 2017. https://digital.library.unt.edu/ark:/67531/metadc1011873/.
Full textAbstract:
A matrix of variably processed Fe-30at%Ni was deposited with variations in laser travel speeds as well and laser powers. A complete shift in phase stability occurred as a function of varying laser travel speed. At slow travel speeds, the microstructure was dominated by a columnar fcc phase. Intermediate travel speeds yielded a mixed microstructure comprised of both the columnar fcc and a martensite-like bcc phase. At the fastest travel speed, the microstructure was dominated by the bcc phase. This shift in phase stability subsequently affected the magnetic properties, specifically saturation magnetization. Ni-Fe-Mo and Ni-Fe-V permalloys were deposited from an elemental blend of powders as well. Both systems exhibited featureless microstructures dominated by an fcc phase. Magnetic measurements yielded saturation magnetizations on par with conventionally processed permalloys, however coercivities were significantly larger; this difference is attributed to microstructural defects that occur during the additive manufacturing process.
2
Hong, Zhihan, and Rongguang Liang. "IR-laser assisted additive freeform optics manufacturing." NATURE PUBLISHING GROUP, 2017. http://hdl.handle.net/10150/625522.
Full textAbstract:
Computer-controlled additive manufacturing (AM) processes, also known as three-dimensional (3D) printing, create 3D objects by the successive adding of a material or materials. While there have been tremendous developments in AM, the 3D printing of optics is lagging due to the limits in materials and tight requirements for optical applicaitons. We propose a new precision additive freeform optics manufacturing (AFOM) method using an pulsed infrared (IR) laser. Compared to ultraviolet (UV) curable materials, thermally curable optical silicones have a number of advantages, such as strong UV stability, non-yellowing, and high transmission, making it particularly suitable for optical applications. Pulsed IR laser radiation offers a distinct advantage in processing optical silicones, as the high peak intensity achieved in the focal region allows for curing the material quickly, while the brief duration of the lasermaterial interaction creates a negligible heat-affected zone.
3
Foster, Moira. "Defect Detection in Selective Laser Melting." DigitalCommons@CalPoly, 2018. https://digitalcommons.calpoly.edu/theses/1874.
Full textAbstract:
Additively manufactured parts produced using selective laser melting (SLM) are prone to defects created during the build process due to part shrinkage while cooling. Currently defects are found only after the part is removed from the printer. To determine whether cracks can be detected before a print is completed, this project developed print parameters to print a test coupon with inherent defects – warpage and cracking. Data recorded during the build was then characterized to determine when the defects occurred.
The test coupon was printed using two sets of print parameters developed to control the severity of warpage and cracking. The builds were monitored using an accelerometer recording at 12500 samples per second, an iphone recording audio at 48000 samples a second, and a camera taking a photo every build layer. Data was analyzed using image comparison, signal amplitude, Fourier Transform, and Wavelet Decomposition.
The developed print parameters reduced warpage in the part by better distributing heat throughout the build envelope. Reducing warpage enabled the lower portion of the part to be printed intact, preserving it to experience cracking later in the build. From physical evidence on the part as well as time stamps from the machine script, several high energy impulse events in the accelerometer data were determined to be when cracking occurred in the build. This project’s preliminary investigation of accelerometers to detect defects in selective laser melting will be used in future work to create machine learning algorithms that would control the machine in real time and address defects as they arise.
4
Pereira, M. F. V. T., M. Williams, and R. Bruwer. "Rapid die manufacturing using direct laser metal deposition." Journal for New Generation Sciences, Vol 7, Issue 3: Central University of Technology, Free State, Bloemfontein, 2009. http://hdl.handle.net/11462/542.
Full textAbstract:
Published ArticleGlobal issues such as energy and climate changes have impacted on both the automotive and aerospace industries, forcing them to adopt measures to produce products that consume fewer combustibles and emit less carbon dioxide. Making vehicles lighter is one of the logical ways of reducing fuel consumption. The need for light components, able to fulfil technical and quality specifications, led to market growth for tooling that is able to mass produce parts using manufacturing processes such as high pressure die casting. Competitive pressures to reduce the lead time required for tooling-up has also increased dramatically. For this reason research into various methods, techniques and approaches to tool manufacture is being undertaken globally. This paper highlights the work undertaken at the CSIR on the issue of rapid die manufacturing through the application and evaluation of a rapid prototyping technique and coating technologies applied to die components of a high pressure casting die for the production of aluminium components. Criteria for determining suitability were developed against which the technique was evaluated that included time, cost and life-expectancy. Results of accelerated testing procedures to evaluate the die material produced by the rapid prototyping technique and surface coatings and treatments of die materials for their resistance to washout, erosion, heat checking and corrosion in a high pressure die casting environment, are presented. The outcomes of this research will be used for further development and application of specific techniques, design principles and criteria for this approach.
5
Lee, Yousub. "Simulation of Laser Additive Manufacturing and its Applications." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1440360229.
Full text
6
Shannon, Geoff. "Laser welding of sheet steel." Thesis, University of Liverpool, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240883.
Full text
7
Murphy, M. L. "Rapid prototyping by laser surface cladding." Thesis, University of Liverpool, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284268.
Full textAbstract:
In recent years rapid prototyping technology has been implemented in many spheres of industry, particularly the field of product development. Existing process provide the capability to rapidly produce a tangible solid part, directly from three dimensional CAD data, from a range of nonmetallic materials. In many situations the desired end product of a development cycle is a metallic object, whether a component or a tool. The development of a system capable of the direct manufacture of fully dense, metal parts is therefore seen as an important landmark in the evolution of rapid prototyping technology. A unique experimental project has been carried out to investigate the potential of laser surface cladding by pneumatic powder delivery to form the basis for such a process. A layered manufacturing part building strategy is proposed, in which laser cladding is used to deposit the near net shape of each layer. Conventional machining techniques are then used to trim each layer to the exact dimensions specified by the CAD data. A multi-kilowatt carbon dioxide laser was integrated with a four axis machine tool to create an opto-mechanical workstation on which to perform the process. A detailed study of the effects of cladding process parameters on the geometry of the deposited metal was carried out and quantitative relationships derived. These relationships are used to select process parameters appropriate to the geometry of the deposition required. A numerical method to fully describe the deposited clad geometry was developed in order that efficient cutter paths could be generated for the back machining cycle. These relationships are also used to determine the minimum size of deposited bead from which the required layer section may be machined, in order to optimise process efficiency. The application of the technique to the generation of a variety of simple geometries was investigated and the potential problems identified. A preliminary investigation into the process accuracy is made, relating specifically to the predictability of the geometry of multiple layer depositions and the distortion of parts as subsequent layers are deposited. The limits of geometrical complexity possible with the current apparatus, and the unsatisfactory build times involved, suggest that the most attractive application of this technique is as part of a hybrid process, adding a novel additive dimension to existing automated fabrication techniques.
8
Iravani, Ebrahim. "Laser and eddy current measuring techniques for agile manufacturing." Doctoral thesis, KTH, Production Engineering, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3312.
Full text
9
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.
Full text
10
Bourchas, Konstantinos. "Manufacturing Effects on Iron Losses in Electrical Machines." Thesis, KTH, Elektrisk energiomvandling, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-172373.
Full textAbstract:
In this master thesis, the magnetic properties of SiFe laminations after cutting and welding are studied. The permeability and the iron loss density are investigated since they are critical characteristics for the performance of electrical machines. The magnetic measurements are conducted on an Epstein frame for sinusoidal variations of the magnetic ux density at frequencies of 50, 100 and 200 Hz, according to IEC 404-2. Mechanical cutting with guillotine and cutting by means of ber and CO2 laser are performed. The inuence of the ber laser settings is also investigated. Especially the assisting gas pressure and the power, speed and frequency of the laser beam are considered. In order to increase the cutting e ect, the specimens include Epstein strips with 1, 2 and 3 additional cutting edges along their length. It is found that mechanical cutting degrades the magnetic properties of the material less than laser cutting. For 1.8% Si laminations, mechanical cutting causes up to 35% higher iron loss density and 63% lower permeability, compared to standard Epstein strips (30 mm wide). The corresponding degradation for laser cut laminations is 65% iron loss density increase and 65% permeability drop. Material of lower thickness but with the same Si-content shows lower magnetic deterioration. Additionally, laser cutting with high-power/high-speed characteristics leads to the best magnetic characteristics among 15 laser settings. High speed settings have positive impact on productivity, since the cutting time decreases. The inuence of welding is investigated by means of Epstein measurements. The test specimens include strips with 1, 3, 5 and 10 welding points. Experiments show an iron loss increase up to 50% with a corresponding 62% reduction in the permeability. A model that incorporates the cutting e ect is developed and implemented in a FEMbased motor design software. Simulations are made for a reference induction motor. The results indicate a 30% increase in the iron losses compared to a model that does not consider the cutting e ect. In case of laser cut core laminations, this increase reaches 50%. The degradation prole considers also the deteriorated magnetizing properties. This leads to increased nominal current up to 1.7% for mechanically cut laminations and 3.4% for laser cut laI detta examensarbete studeras hur de magnetiska egenskaperna hos SiFe-plat paverkas av skarning och svetsning. Permeabilitet och jarnforlustdensitet undersoks eftersom de ar kritiska variabler for elektriska maskiners prestanda. De magnetiska matningarna genomfordes pa en Epstein ram med en odesfrekvens pa 50, 100 och 200 Hz, enligt IEC 404-2. E ekterna av mekanisk skarning med giljotin samt skarning med ber- och CO2-laser studerades. Inverkan av olika berlaserinstallningar undersoktes ocksa genom att variera gastrycket, skarhastigheten samt frekvensen och e ekten av laserstralen. For att oka skare ekten inkluderades Epsteinremsor med ytterligare 1, 2 och 3 langsgaende skarsnitt. Det visas att mekanisk skarning har en mindre paverkan pa de magnetiska egenskaperna hos materialet an vad laserskarning har. Matningar pa plat med 1.8% Si visar att da prov med tre extra langsgaende giljotinklipp anvands kan permeabiliteten reduceras med upp till 63% och jarnforlusterna kan oka med upp till 35%. Motsvarande resultat for laserskurna platar visar en permeabilitetsreduktion pa upp till 65% och en jarnforlustokning pa upp till 65%. Ur studien av de tva studerade skarprocesserna framkommer aven att tunnare plat paverkas mindre negativt an tjockare plat. Ett antal olika installningar har provats for att utreda hur olika parametrar paverkar e ekterna av laserskarning. Studien indikerar att skarning med hog e ekt och hog hastighet ger den minsta paverkan pa materialets magnetiska egenskaper. Vilket aven har en positiv inverkan pa produktiviteten vid laserskarning. Epsteinprover har aven utforts for att undersoka vilka e ekter som introduceras da SiFe-plat svetsas. Provstyckena bestod av remsor med en, tre, fem och 10 svetspunkter. Experimenten visar en jarnforlustokning med upp till 50% samt en permeabilitetsreduktion upp till 62% da platarna svetsats samman tva och tva. En modell for att studera e ekterna av de forandrade materialegenskaperna vid skarning pa en induktionsmotor utvecklas och implementeras i en FEM-baserad mjukvara. Resultaten tyder pa en jarnforlustokning med 30% da skare ekten orsakad av giljotin beaktas. Vid simulering av laserskuren plat kan denna okning vara sa stor som 50%. Det framkommer aven att laserskarningen kan reducera e ektfaktorn sa mycket som 2.6%.
11
Li, Lin. "Intelligent laser cladding control system design and construction." Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/7683.
Full text
12
Duran, Olga. "Automated camera/laser-based pipe inspection." Thesis, King's College London (University of London), 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.407464.
Full text
13
Voisey, Kathleen Theresa O'Sullivan. "Laser drilling of metals and ceramics." Thesis, University of Cambridge, 2002. https://www.repository.cam.ac.uk/handle/1810/272329.
Full text
14
Ren, Lan. "Integrated process planning for a hybrid manufacturing system." Diss., Rolla, Mo. : Missouri University of Science and Technology, 2008. http://scholarsmine.mst.edu/thesis/pdf/Ren_09007dcc8046714a.pdf.
Full textAbstract:
Thesis (Ph. D.)--Missouri University of Science and Technology, 2008.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed April 18, 2008) Includes bibliographical references.
15
Roberts, Ibiye Aseibichin. "Investigation of residual stresses in the laser melting of metal powders in additive layer manufacturing." Thesis, University of Wolverhampton, 2012. http://hdl.handle.net/2436/254913.
Full textAbstract:
Laser Melting (LM) is an Additive Layer Manufacturing (ALM) process used to produce three-dimensional parts from metal powders by fusing the material in a layerby- layer manner controlled by a CAD model. During LM, rapid temperature cycles and steep temperature gradients occur in the scanned layers. Temperature gradients induce thermal stresses which remain in the part upon completion of the process (i.e. residual stresses). These residual stresses can be detrimental to the functionality and structural integrity of the built parts. The work presented in this thesis developed a finite element model for the purpose of investigating the development of the thermal and residual stresses in the laser melting of metal powders. ANSYS Mechanical software was utilised in performing coupled thermal-structural field analyses. The temperature history was predicted by modelling the interaction of the moving laser heat source with the metal powders and base platform. An innovative ‘element birth and death’ technique was employed to simulate the addition of layers with time. Temperature dependent material properties and strain hardening effects were also considered. The temperature field results were then used for the structural field analysis to predict the residual stresses and displacements. Experiments involving laser melting Ti-6Al-4V powder on a steel platform were performed. Surface topography analyses using a laser scanning confocal microscope were carried out to validate the numerically predicted displacements against surface measurements. The results showed that the material strain hardening model had a direct effect on the accuracy of the predicted displacement results. Using the numerical model, parametric studies were carried out to investigate the effects of a number of process variables on the magnitude of the residual stresses in the built layers. The studies showed that: (i) the average residual stresses increased with the number of melted powder layers, (ii) increasing the chamber temperature to 300°C halved the longitudinal stresses. At 300°C, compressive stresses appeared on the Ti64 surface layer, (iii) reducing the raster length from 1 mm to 0.5 mm reduced the average longitudinal stress in the top layer by 51 MPa (0.04σy), (iv) reducing the laser scan speed from 1200 mm/s to 800 mm/s increased the longitudinal stress by 57 MPa (0.05σy) but reduced the transverse stress by 46 MPa (0.04σy).
16
Svedberger, Johan, and Jonas Andersson. "Laser scanning in manufacturing industries : The potential and usability of laser scanning for industrial applications." Thesis, KTH, Industriell produktion, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-134954.
Full textAbstract:
Making mistakes or discovering errors too late in the factory layout process is very costly. Unfortunately, the layouts aren’t always accurate or updated which creates a degree of uncertainty when it comes to installation of new equipment and rebuilding facilities. It also leads to a lot of waste in movement when employees has to go out in production to perform measurements, take pictures and take notes in order to remember important details to avoid errors. Lasers in land and engineering surveying instruments have been widely used for the last 30 years. A natural development has been to add a scanning mechanism to a total station that were already equipped with laser rangefinders and angular encoders, allowing automated measurement and location of thousands of nonspecific points. The automobile industry has begun to see the potential of laser scanning, mainly because of the development of the software handling the scan results, the point clouds. Scania, in collaboration with the FFI research project at the Royal Institute of Technology (KTH), therefore wanted to investigate how the new possibilities of 3D laser scanning can facilitate the development and maintenance of production systems and how it could be implemented in the current factory design process. By scanning three locations at Scania related to machining, assembly and aftermarket service the usability of the results has been investigated with the software Faro Scene and Bentley Pointools V8i. The results of the study showed that the laser scanning technology can generate several possibilities for manufacturing industries. The technology can be profitable and the modern point cloud software and applications could support the work of the layout design process greatly. Three main application areasfound: Visualization & communication: The point cloud is an excellent information carrier and can easily be used as a visualization aid for meetings or simply to refreshing memories of a location. It also provides the possibility to view and examine a location remotely. Gather information: The measuring possibilities are immense, allowing single point and distance measurements without the concern of interfering with objects. The method can to some extent replace the current approach in measuring buildings and floor flatness. Simulation & verification: Software can perform advanced simulations and verifications of existing and future layouts, models and installations. Parts of the point cloud can be colorized, hidden, removed, duplicated or transformed. Existing 2D layout drawings or 3D models can be attached and verified relative the point cloud. The attached objects can be simulated with clash collision or differencing. Keywords: 3D Laser Scanning, TLS, CAD, Point Cloud, Factory Layout, Faro Scene, Bentley Pointools V8i, FactoryDesign Process, Factory Scanning Process.
17
Aitchison, David Robert. "Laser based cutting tool condition monitoring." Thesis, University of Hull, 1995. http://hydra.hull.ac.uk/resources/hull:3693.
Full text
18
Ranjan, Rajit. "Design for Manufacturing and Topology Optimization in Additive Manufacturing." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439307951.
Full text
19
Zheng, Hong Yu. "In-process quality analysis of laser cutting." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/7792.
Full text
20
Longfield, Nicholas Peter. "An investigation of ultrasonically modified laser welding." Thesis, Coventry University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364684.
Full text
21
Jones, Jason Blair. "Investigation of laser printing for 3D printing and additive manufacturing." Thesis, University of Warwick, 2013. http://wrap.warwick.ac.uk/59733/.
Full textAbstract:
Additive Manufacturing (AM), popularly called “3D printing,” has benefited from many two-dimensional (2D) printing technology developments, but has yet to fully exploit the potential of digital printing techniques. The very essence of AM is accurately forming individual layers and laminating them together. One of the best commercially proven methods for forming complex powder layers is laser printing, which has yet to be used to directly print three-dimensional (3D) objects above the microscale, despite significant endeavour. The core discovery of this PhD is that the electrostatic charge on toner particles, which enables the digital material patterning capabilities of 2D laser printing/photocopying, is disabling for building defect-free 3D objects after the manner attempted to date. Toner charge is not mostly neutralized with fusing as previously assumed. This work characterizes and substantiates the accumulation of residual toner charge as a primary cause for defects arising in 3D printed bodies. Next, various means are assessed to manage and neutralize residual toner charge. Finally, the complementary implementation of charge neutralization with electrostatic transfer methods is explored.
22
Sundqvist, Jesper. "Heat conduction effects during laser welding." Licentiate thesis, Luleå tekniska universitet, Produkt- och produktionsutveckling, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-17902.
Full textAbstract:
Since the invention of the laser in 1960, its use has been growing steadily. New laser sources with high beam power and high beam quality provide potential for further growth. High quality beams can be shaped by optical tools, such as scanners or Diffractive Optical Elements, DOE, to almost any beam shape, enabling innovative laser process solutions. For welding in particular, a tailored beam can be used to control the melt pool and to optimise the temperature field and cycle. For example, joining of electrical components like battery cells becomes more common due to the shift to electrical vehicles. This is a field of applications where laser welding with a tailored beam has high potential due to the need of tightly controlled design tolerances or processing temperatures and in turn electrical and mechanical properties. The research presented in the thesis encompasses the heat flow generated from tailored laser beams, the thermal effects on the weld shape and on other quality criteria, the generated residual stress and its influence on fatigue crack propagation. For the sake of simplicity, melt flow was not considered in the calculations, which was discussed, too. The first three papers apply predictive mathematical modelling for the temperature field while the fourth paper experimentally derives the thermally induced residual stress distribution back from measured fatigue crack propagation.Paper I contains a FEM-based numerical heat flow study of a conduction mode laser welding case where a C-shaped overlap joint is desired. The quality criteria demand the welding process to be tightly controlled in terms of laser power and pulse time. Contrary to expectations, the joint geometry can significantly deviate from the laser beam C shape. As a continuation, in Paper II various quantitative indicators were derived and studied as part of the numerical simulation, in order to identify a suitable beam shape and in turn a DOE-design.Paper III presents a semi-analytical mathematical model that was developed for the heat flow in pulsed conduction mode welding for spatially and temporally shaped laser beams. As an alternative to FEM, the model is fast due to its analytical nature, which enables iterative beam shape optimization and DOE-design. By studying different beam shapes and the induced temperature fields, the potential and limits of the model were demonstrated and discussed. Paper IV is a study on residual stress that is thermally induced during the heating and cooling cycle of laser keyhole welding. Acceleration measurement of the crack propagating across the weld during fatigue testing turned out to be a suitable method to derive the residual stress distribution along the crack, including its alteration during the cracking. Comparisons with FEM-based stress analysis provide a link back to the temperature field induced by the laser, which enables optimization, e.g. by beam shaping.Godkänd; 2015; 20150911 (jessun); Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Jesper Sundqvist Ämne: Produktionsutveckling/Manufacturing System Engineering Uppsats: Heat Conduction Effects During Laser Welding Examinator: Professor Alexander Kaplan, Institutionen för teknikvetenskap och matematik, Avdelning: Produkt- och produktionsutveckling, Luleå tekniska universitet Diskutant: Professor Lars Pejryd, Örebro universitet, Örebro Tid: Tisdag 10 november, 2015 kl 12.30 Plats: E632, Luleå tekniska universitet
23
Burkhardt, Irmela [Verfasser]. "Dissimilar titanium and titanium aluminide joints manufactured by laser beam welding and laser additive manufacturing / Irmela Burkhardt." Hamburg : Universitätsbibliothek der Technischen Universität Hamburg-Harburg, 2021. http://d-nb.info/1224966562/34.
Full text
24
Shiu, Pun Pang. "Controlled-depth laser cutting of aluminum sheet for Laminated-Object Manufacturing." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/MQ63367.pdf.
Full text
25
Syed, Waheed Ul Haq. "Combined wire and powder deposition for laser direct metal additive manufacturing." Thesis, University of Manchester, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.556499.
Full text
26
Starz, Anton Johannes. "A calculation concept to reduce manufacturing cost on laser sintering machines." Thesis, Bloemfontein : Central University of Technology, Free State, 2008. http://hdl.handle.net/11462/117.
Full textAbstract:
Thesis (M. Tech.) - Central University of Technology, Free State, 2008A company’s ability to produce products faster and more economically may lead to a competitive edge in the international market. The reduction of development costs and shortened development time will undeniably depend on effective organisational structures that are based on effective information- and communication techniques and manufacturing technologies. An innovative manufacturing technology that impacts on rapid product development is Rapid Prototyping (RP). The Centre for Rapid Prototyping and Manufacturing (CRPM) works closely with South African companies, supporting them with common mechanical engineering solutions and specialising in the manufacturing of prototypes. One of the options offered in the manufacture of prototypes is the Laser Sintering (LS) process. It is however, difficult to determine the product cost for the building volume used to manufacture the prototypes. Prototypes from different clients can be manufactured at the same time in the same process. The problem however, is how to calculate the costs for each prototype and to offer the clients an accurate quotation for the manufacture of the prototype. Therefore, it is necessary to design a calculation concept, which includes all accrued costs and allocate these to the different parts/prototypes. As it is problematic to calculate the manufacturing cost of prototypes, it is necessary to analyse all the effects, parameters and influences on the manufacturing process in order to determine the manufacturing time, and ultimately the machine costs. This is needed to calculate the total cost of one platform and the cost of each individual part. The project, through various experiments determined how to allocate the costs, through a correlation between part volume and platform height. The aim of the study was to determine a calculation concept to estimate the total platform cost and the cost of each individual part. Furthermore, the estimated cost was compared with the actual cost to determine the deviation between the calculation methods, and lead to a calculation concept that can be used to predict and reduce the manufacturing costs. The results obtained from the research were used for an exact calculation and reduction of prototype unit costs manufactured on LS machines, which gave three basic advantages: * Manufacturing costs were reduced to benefit clients, which meant that they could invest more in the design of new prototypes and products, to improve customer satisfaction * Prototype manufacturing on expensive RP machines could be optimised by using more prototypes and lower costs for entering the market. * The calculation risk could be minimised, which lowered the risk of losing money on a project and resulted in better planning for available resources.
27
Juhasz, Michael J. "In and Ex-Situ Process Development in Laser-Based Additive Manufacturing." Youngstown State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ysu15870552278358.
Full text
28
Langer, H. J., and M. Shellabear. "Recent e-Manufacturing solutions developed by EOS." Journal for New Generation Sciences, Vol 4, Issue 1: Central University of Technology, Free State, Bloemfontein, 2006. http://hdl.handle.net/11462/492.
Full textAbstract:
Published Articlee-Manufacturing means the fast, flexible and cost-effective production of parts directly from electronic data, which can include rapid prototyping, rapid tooling, (spare) parts on demand etc. Especially interesting is the direct manufacture of enduse parts. In this paper, recent case studies will be presented showing commercial e-Manufacturing projects including small production batches and mass customized series production from various industrial branches. The paper also discusses the relevance of several recent technological innovations in laser-sintering for e- Manufacturing, especially how increasing the productivity of machines and process chains has increased the range of applications which are cost-effective using lasersintering.
Case studies include:
- small series production (up to a few thousand p.a.) of products
- production of customized (one-off) products
- mass production of customer-specific (mass customized) products
- optimized tooling concepts for production of up to millions of products
29
Ryder, Gerard Joseph. "A numerical model of the selective laser sintering process." Thesis, University of Leeds, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271961.
Full text
30
Lamas, Javier. "Analysis of laser arc hybrid welding experiments." Licentiate thesis, Luleå tekniska universitet, Produkt- och produktionsutveckling, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26147.
Full textAbstract:
The thesis is about the analysis of experimental results on the laser arc hybrid welding (LAHW) process as well as about the methodology and tools behind. Due to the high potential on weld penetration and welding speed, the industrial importance of LAHW techniques has been increasing in the recent years. However the massive use of them is constrained because of high investment costs, complexity and novelty. These obstacles provoke a lack of experienced operators and they desire a base of knowledge related to optimal parameters to obtain good quality welds. In this scenario, understanding of the physical LAHW phenomena has been proven useful for better control of the process,particularly to predict and avoid groups of parameters that can originate defects. For this reason, it is valuable to carry out experiments and to systematize the analysis methods.The presented work is focused on the impact of geometrical joint fit-up properties on the weld surface quality. The papers included here are organized as a comprehensive study of the effects and impact of various geometrical aspects of the laser-arc-workpiece arrangement on the surface quality of the welds, i.e. tracking from joint fit-up tolerances like gap width to critical weld shape aspects like undercuts via observation of fluid flow at the weld pool surface. Three frequent and critical geometrical aspects were identified from industrial edge preparation, namely gap width variations, vertical edgemismatch and vertical plate position to the laser-arc tool. These aspects can cause defects when the surface is bended or when the LAHW tool is automatically moved. Although in production they arise all simultaneously, to understand the respective contribution, systematic experiments were designed. These experiments were carried out to measure and surpass the stability threshold related to each aspect, to observe the flow behaviour and to evaluate the physical phenomena related to weld bead formation.The three Papers I, II, III describe a systematic methodology based on High Speed Imaging, HSI, on quantitative weld surface measurement obtained from a laser triangulation scanner and on statistical analysis of different experimental results. This methodology is based on the observation, measurement, automatic location and calculation of fundamental bead variables (top and root undercuts, reinforcement, melt pool length, pool width and flow speed, or mass balance) related to the melt flow.In Paper I, using a pulsed arc mode, the effects of increasing the standoff between the LAHW tool and the workpiece are described and a mechanism is identified to explain the flow behaviour and its consequences on the resulting weld pool shape. In Paper II, again using pulsed arc mode in LAHW, the effects of the vertical edge mismatch and of the gap width on the weld pool shape are described, again followed by a theoretical description. Paper III compares the pulsed arc mode with the CMT mode in LAHW,again for the effect of the gap width on the weld surface shape, in particular the top bridging phenomenon that was identified. Also these results are theoretically described, explaining the mechanisms via HSI.Altogether, the three papers comprise a theoretical description of the LAHW weld shape behaviour and weld quality depending on the fit-up tolerances, based on experimental evidence and analysis. From this chain of evidence and associated understanding, conclusions were drawn and practical guidelines were derived.Godkänd; 2014; 20141112 (alka); Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Javier Lamas Ämne: Produktionsutveckling/Manufacturing Systems Engineering Uppsats: Analysis of Laser Arc Hybrid Welding Experiments Examinator: Professor Alexander Kaplan, Institutionen för teknikvetenskap och matematik, Luleå Tekniska universitet Diskutant: Professor Petri Vuoristo, Tammerfors tekniska universitet Tid: Torsdag den 18 december 2014 kl 09.30 Plats: E206, Luleå tekniska universitet
31
Ivarson, Anders. "Laser cutting: an experimental and theoretical investigation." Licentiate thesis, Luleå, 1991. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-16891.
Full text
32
Lampa, Conny. "Practical and theoretical aspects of laser welding." Licentiate thesis, Luleå tekniska universitet, 1995. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26605.
Full text
33
Gouveia, H. N. "The coupling mechanisms in the CO2 laser welding of copper." Thesis, Cranfield University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282175.
Full text
34
Gerber, G. F., and L. J. Barnard. "Designing for laser sintering." Journal for New Generation Sciences, Vol 6, Issue 2: Central University of Technology, Free State, Bloemfontein, 2008. http://hdl.handle.net/11462/504.
Full textAbstract:
Published ArticleUntil recently solid freeform fabrication (SFF) technology has been used mostly for production of prototype parts. However, as this technology matures, the initiative of utilising it for the manufacture of end-use products is establishing itself. As this tendency to use SFF for actual production runs increases, a demand is developing for sets of process-specific design for manufacture (DFM) guidelines that will assist designers who are designing parts for manufacture by a specific rapid manufacturing (RM) process. The purpose of this paper is to provideRMdesigners with such a series of processspecific design for manufacture guidelines.
35
Birt, Aaron M. "Materials & Machines: Simplifying the Mosaic of Modern Manufacturing." Digital WPI, 2017. https://digitalcommons.wpi.edu/etd-dissertations/542.
Full textAbstract:
Manufacturing in modern society has taken on a different role than in previous generations. Today’s manufacturing processes involve many different physical phenomenon working in concert to produce the best possible material properties. It is the role of the materials engineer to evaluate, develop, and optimize applications for the successful commercialization of any potential materials. Laser-assisted cold spray (LACS) is a solid state manufacturing process relying on the impact of supersonic particles onto a laser heated surface to create coatings and near net structures. A process such as this that involves thermodynamics, fluid dynamics, heat transfer, diffusion, localized melting, deformation, and recrystallization is the perfect target for developing a data science framework for enabling rapid application development with the purpose of commercializing such a complex technology in a much shorter timescale than was previously possible. A general framework for such an approach will be discussed, followed by the execution of the framework for LACS. Results from the development of such a materials engineering model will be discussed as they relate to the methods used, the effectiveness of the final fitted model, and the application of such a model to solving modern materials engineering challenges.
36
Park, Jae-hyoung. "Process planning for laser chemical vapor deposition." Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/18367.
Full text
37
Karlin, Joseph H. (Joseph Howard). "3D imaging methods for manufacturing, with emphasis on the laser speckle technique." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/38074.
Full text
38
Gee, Kaitlyn Elizabeth. "Numerical tools for rate-cost-quality analysis of laser-based additive manufacturing." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127160.
Full textAbstract:
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, May, 2020Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 81-84).
AM expands the design space in an unprecedented manner, as it can allow complex internal geometries, support multiple materials or structural gradients, significantly reduce lead times for small-batch production, and enable mass customization [1]. However, the adoption of AM in industry is hindered by our lack of design knowledge and inability to navigate the myriad considerations required to reliably produce high quality AM components economically. To quantitatively assess the tradeoffs between build rate, resolution and cost for AM processes, we present a physics-based rate and cost estimator for scanning laser based AM. The model takes a mesh representation of the part design as input, and uses a parametrized model of the rate-limiting physics of the build process to estimate the part-specific build time [2] [3]. From this build time estimate, per-part cost is calculated using a quantity-dependent activity-based model [4]. The model thus enables parametric analysis of tradeoffs between part quality (e.g., resolution), throughput, and cost. Additionally, we develop an analytical model to quantify the number of melting cycles the part undergoes during the print process as a metric of print quality. Integrated with our physics-based build time estimator, we articulate the tradeoff between build rate and print quality as a direct function of material properties, machine specifications, and print parameter selection. By conceptualizing and quantifying the relationships between part design, manufacturability, and cost, the computational design and decision-making tools developed here will enable optimal use of AM in real-world, production contexts. Given the complexity of designing for AM, these results produce valuable insight into otherwise complicated relationships between rate, cost and quality for SLM. For industry, this work will enable faster, cost-effective product production by identifying the most desirable print parameter sets.
by Kaitlyn Elizabeth Gee.
S.M.
S.M. Massachusetts Institute of Technology, Department of Mechanical Engineering
39
Yadroitsau, Ihar. "Direct manufacturing of 3D objects by selective laser melting of metal powders." Saint-Etienne, 2008. http://www.theses.fr/2008STET4006.
Full textAbstract:
The accomplished doctoral study concerns the interaction of the powerful laser radiation with powder metallic materials. The problem is of a great scientific interest, since it is a multi-disciplinary subject integrating powder metallurgy, thermo-physics, radiation and heat tranfer, phase transformations. Along with this, the subject has a considerable practical interest because Laser-assisted Direct Manufacturing based on Selective Laser Melting (SLM) is an emerging technology for manufacturing 3D functional objects with great added value, and also complex customized parts. Systematic study is accomplished for the powder materials currently employed in laser-assisted direct manufacturing : stainless steel 316L (-25 µm), tool steel H13 (-25 µm), Inconel 718 (-25 µm), CuNi10 (-25 µm), titanium grade 2 (-25 µm) and NiTi (-45 µm) ; stainless steel 904L (-16 µm et -7 µm), Inconel 625 (-16 µm), Co212F (CoCr, -31 µm). The above mentioned powders were employed in the experimental study for fabrication of 2D planar objects, 3D models and functional components. Comprehensive experimental research on laser-matter interaction are carried out for interaction of a powerful (0. 3-1. 3x106 W/cm²) moving laser beam with a complex system « metallic powder on solid metallic substrate ». Manufacturing strategies allowing 100% density on the fabricated objects are found. Optimal parameters for stable SLM process are determinedL'objectif principal de la thèse de doctorat présentée dans ce mémoire est l'étude de l'interaction d'un faisceau laser de puissance avec des poudres métalliques. Le sujet est d'un grand intérêt scientifique par sa multidisciplinarité intégrant la métallurgie de poudres, la physique thermique, le transfert de chaleur et radiatif, la transformation de phases. En même temps, le sujet a une signification pratique considérable car la Fabrication Directe par fusion laser sélective des poudres (SLM) est une technologie émergente de fabrication d'objets 3D avec une grande valeur ajoutée et de pièces fonctionnelles complexes sur mesure. Une étude systématique a été réalisée sur les poudres actuellement utilisées dans la Fabrication Directe assistée par laser : Inox 316L (-25 µm), acier d'outillage H13 (-25 µm), Inconel 718 (-25 µm), CuNi10 (-25 µm), Ti grade 2 (-25 µm) et NiTi (-45 µm) ; Inox 904L (-16 µm et -7 µm), Inconel 625 (-16 µm), Co212F (CoCr, -31 µm). A partir de ces poudres, des objets plats 2D, des modèles 3D et des pièces fonctionnelles ont été fabriqués. Des recherches expérimentales approfondies sur l'interaction laser/matière sont effectuées, plus particulièrement sur l'interaction d'un faisceau laser de haute puissance mobile (0. 3-1. 3x106 W/cm²) avec un système complexe de poudres métalliques sur substrat métallique solide. Les stratégies de fabrication permettant d'obtenir la densité 100% de pièces résultantes sont identifiées. Les paramètres optimaux pour assurer la stabilité du procédé SLM sont définis
40
Attar, Hooyar. "Manufacturing and properties of titanium-based materials produced by selective laser melting." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2015. https://ro.ecu.edu.au/theses/1596.
Full textAbstract:
This PhD study firstly presents the results of using selective laser melting (SLM) to produce commercially pure titanium (CP-Ti) parts. Accurate manipulation of SLM parameters is applied to produce nearly fully dense (>99.5%) CP-Ti parts without any posttreatments. Compared with output from traditional technologies, the microhardness, compressive and tensile strengths of SLM-processed CP-Ti parts have been improved to 261 Hv, 1136 MPa and 757 MPa, respectively, due to the formation of refined martensitic α΄ grains during SLM. Optimizing manufacturing parameters could enhance the strength and hardness of CP-Ti while maintaining its ductility. Fractography study of the tensilefailed specimens showed that incompletely melted particles and porosities caused early fracture in porous samples. Mixture of dimples and minor quasi-cleavage facets covered most fracture surface in fully dense samples.
Secondly, optimized tuning of the SLM manufacturing parameters achieved almost fully dense in-situ Ti-TiB composites from optimally milled Ti-TiB2 powder. X-ray and electron diffraction patterns as well as microstructural investigations indicated a chemical reaction during SLM in which irregular-shape titanium diboride (TiB2) particles react with pure Ti to form needle-shape TiB particles. Transmission electron microscopy (TEM) investigations revealed that Ti grains are refined significantly due to the existence of B. The microhardness, yield strength and compressive strength of the SLM-produced Ti-TiB composites increased to 402 Hv, 1103 MPa and 1421 MPa, respectively, compared to those of SLM-produced CP-Ti parts. These improvements are mainly due to strengthening and hardening effects induced by TiB particles and refinement of Ti grains. Fractography analyses showed that a mixture of splitting/shearing and smooth/rough zones covers the fracture surfaces of failed composite samples after compression testing.
Thirdly, SLM, powder metallurgy (PM) and casting technologies were applied to produce Ti-TiB composite parts from Ti-TiB2 powder. The ultimate compressive strength of SLM-processed and cast samples were 1421 MPa and 1434 MPa respectively, whereas the ultimate strengths of PM-processed 25%, 29% and 36% porous samples were 510 MPa, 414 MPa and 310 MPa respectively. Young’s modulus for porous composite samples were 70 GPa, 45 GPa and 23 GPa, for 25%, 29% and 36% porosity levels respectively which are lower than those of SLM-processed (145 GPa) and cast (142 GPa) samples. Fracture analysis of the SLM-processed and cast samples showed similar features but failure of porous samples occurred due to porosities and weak bonds among particles.
Fourthly, CP-Ti and Ti-TiB composite specimens with different porosity levels were obtained by SLM. Young’s moduli and yielding strengths of tested porous samples decreased with increasing of porosity and are observed in the range of 120-963 MPa and 12-68 GPa respectively for CP-Ti and 234‒767 MPa and 25‒84 GPa respectively for Ti- TiB. Elastic moduli of both 37% porous CP-Ti and Ti-TiB samples are close to that of human bone, leading to reduce stiffness mismatch between implant and bone.
This research demonstrates that SLM is a promising method for fabricating titanium-based samples with superior mechanical properties (i.e. tensile, compression and hardness) to those produced by casting and powder metallurgy techniques, thus improving the reliability of the SLM process for biomedical applications.
41
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.
Full text
42
Markusson, Lisa. "Powder Characterization for Additive Manufacturing Processes." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-62683.
Full textAbstract:
The aim of this master thesis project was to statistically correlate various powder characteristics to the quality of additively manufactured parts. An additional goal of this project was to find a potential second source supplier of powder for GKN Aerospace Sweden in Trollhättan. Five Inconel® alloy 718 powders from four individual powder suppliers have been analyzed in this project regarding powder characteristics such as: morphology, porosity, size distribution, flowability and bulk properties. One powder out of the five, Powder C, is currently used in production at GKN and functions as a reference. The five powders were additively manufactured by the process of laser metal deposition according to a pre-programmed model utilized at GKN Aerospace Sweden in Trollhättan. Five plates were produced per powder and each cut to obtain three area sections to analyze, giving a total of fifteen area sections per powder. The quality of deposited parts was assessed by means of their porosity content, powder efficiency, geometry and microstructure. The final step was to statistically evaluate the results through the analysis methods of Analysis of Variance (ANOVA) and simple linear regression with the software Minitab. The method of ANOVA found a statistical significant difference between the five powders regarding their experimental results. This made it possible to compare the five powders against each other. Statistical correlations by simple linear regression analysis were found between various powder characteristics and quality of deposited part. This led to the conclusion that GKN should consider additions to current powder material specification by powder characteristics such as: particle morphology, powder porosity and flowability measurements by a rheometer. One powder was found to have the potential of becoming a second source supplier to GKN, namely Powder A. Powder A had overall good powder properties such as smooth and spherical particles, high particle density at 99,94% and good flowability. The deposited parts with Powder A also showed the lowest amount of pores compared to Powder C, a total of 78 in all five plates, and sufficient powder efficiency at 81,6%.
43
Jamal, Naim Musa. "Finite element analysis of curl development in the selective laser sintering process." Thesis, University of Leeds, 2001. http://etheses.whiterose.ac.uk/304/.
Full textAbstract:
Selective laser sintering (SLS) is a rapid prototyping process, which operates by using a laser to locally heat an area within a layer of powder material, causing it to fuse together, creating a thin cross-section of solid material. 3D shapes are built by repeatedly depositing a layer of fresh powder on top of the cross-section and then locally heating it, causing it to fuse together and to the layer beneath. However, during SLS processing, temperature differences that exist in different regions of the fabricated parts lead to uneven shrinkages. The shrinkages cause surfaces in the part, which are intended to be flat, to exhibit a curved profile; a phenomenon termed curl. The development of curl is highly influenced by the SLS machine parameters selected in fabrication. The production of geometrically acceptable parts involves numerous fabrication trials before the optimum machine parameters can be found. The procedure can be time consuming and expensive. The aim of the work presented in this thesis was to develop finite element models for the purpose of predicting curl in SLS fabricated polycarbonate parts. The ultimate goal was to use the models to estimate the optimum SLS machine parameters for the physical fabrication of geometrically acceptable parts, produced in any material, and therefore avoid the costly and time consuming process of using SLS machines for experimental purposes. The prediction of curl was made through heat transfer and stress finite element models that were both coupled using the sequentially coupled thermal-stress analysis technique. Experimental work was carried out to measure material properties used as input to the models and to validate results predicted. The sensitivity of curl predicted to assumptions considered in the heat and stress models was introduced, and the assumptions highly influencing the accuracy of curl predictions were identified.
44
Hussein, Ahmed Yussuf. "The development of lightweight cellular structures for metal additive manufacturing." Thesis, University of Exeter, 2013. http://hdl.handle.net/10871/15023.
Full textAbstract:
Metal Additive Manufacturing (AM) technologies in particular powder bed fusion processes such as Selective Laser Melting (SLM) and Direct Metal Laser Sintering (DMLS) are capable of producing a fully-dense metal components directly from computer-aided design (CAD) model without the need of tooling. This unique capability offered by metal AM has allowed the manufacture of inter-connected lattice structures from metallic materials for different applications including, medical implants and aerospace lightweight components. Despite the many promising design freedoms, metal AM still faces some major technical and design barriers in building complex structures with overhang geometries. Any overhang geometry which exceeds the minimum allowable build angle must be supported. The function of support structure is to prevent the newly melted layer from curling due to thermal stresses by anchoring it in place. External support structures are usually removed from the part after the build; however, internal support structures are difficult or impossible to remove. These limitations are in contrast to what is perceived by designers as metal AM being able to generate all conceivable geometries. Because support structures consume expensive raw materials, use a considerable amount of laser consolidation energy, there is considerable interest in design optimisation of support structure to minimize the build time, energy, and material consumption. Similarly there is growing demand of developing more advanced and lightweight cellular structures which are self-supporting and manufacturable in wider range of cell sizes and volume fractions using metal AM. The main focuses of this research is to tackle the process limitation in metal AM and promote design freedom through advanced self-supporting and low-density Triply Periodic Minimal Surface (TPMS) cellular structures. Low density uniform, and graded, cellular structures have been developed for metal AM processes. This work presents comprehensive experimental test conducted in SLM and DMLS processes using different TPMS cell topologies and materials. This research has contributed to new knowledge in understanding the manufacturability and mechanical behaviour of TPMS cellular structures with varying cell sizes, orientations and volume fractions. The new support structure method will address the saving of material (via low volume cellular structures and easy removal of powder) and saving of energy (via reduced build-time).
45
Pocorni, Jetro. "Experimental and theoretical investigation of the laser cutting process." Licentiate thesis, Luleå tekniska universitet, Produkt- och produktionsutveckling, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26654.
Full textAbstract:
This thesis concerns experimental investigations of laser cutting with theoretical and practical discussions of the results. The thesis is made up of three papers which are linked in such a way that each of them studies a different aspect of laser cutting: In paper I the two major laser types in cutting, namely CO2 and fiber lasers, are compared to each other by a self-defined cut efficiency. Next in paper II the laser cutting process is observed with a high speed imaging, HSI, camera to give information about the melt flow in the cut zone. In paper III the initiation of the laser cutting process, called piercing, is studied. Paper I is about investigating the effect of material type, material thickness, laser wavelength, and laser power on the efficiency of the cutting process for industrial state-of-the-art cutting machines. Here the cutting efficiency is defined in its most fundamental terms: as the area of cut edge created per Joule of laser energy. This paper presents phenomenological explanations for the relative cutting efficiencies of fiber lasers and CO2 lasers and the mechanisms affecting these efficiencies for stainless steels and mild steel over a range of thicknesses. The paper also involves a discussion of both theoretical and practical engineering issues.In Paper II a new experimental technique has been developed which enables High Speed Imaging of laser cut fronts produced using standard, commercial parameters. The results presented here suggest that the cut front produced when cutting 10 mm thick medium section stainless steel with a fibre laser and a nitrogen assist gas is covered in humps which themselves are covered in a thin layer of liquid. A combination of HSI results and theoretical analysis has revealed that these humps move down the cut front at an average speed which is a factor three less than the liquid flow speed. Paper III addresses a specific topic: Before any cut is started the laser needs to pierce the material. The two most important aspects of the piercing process are: a) How long does it take to pierce the material? And b) How wide is the pierced hole? If the hole is no wider than the cut line, the material can be pierced on the line to be cut. In this paper the laser piercing process is investigated using a wide range of laser pulse parameters, for stainless steel using a fibre laser, to discover their influence on pierce time and pierced hole diameter. A high speed imaging camera is used to time the penetration event and to study the laser-material interactions involved in drilling the pierced holes. Optimum parameters have been identified for both pierce time and pierce hole width.Godkänd; 2015; 20151012 (jetpoc); Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Jetro Pocorni Ämne: Produktionsutveckling/Manufacturing Systems Engineering Uppsats: Experimental and Theoretical Investigation of the Laser Cutting Process Third-cycle subject area: Manufacturing System Engineering Examinator: Professor Alexander Kaplan, Institutionen för teknikvetenskap och matematik, Avdelning: Produkt- och produktionsutveckling, Luleå tekniska universitet. Diskutant: PhD Ali Khan, TWI Ltd, Cambridge, UK Tid: Fredag 11 december, 2015 kl 09.30 Plats: E246, Luleå tekniska universitet
46
Wouters, Marc. "Hybrid laser-MIG welding : an investigation of geometrical considerations." Licentiate thesis, Luleå, 2005. http://epubl.luth.se/1402-1757/2005/82.
Full text
47
Wang, Dapeng. "High-resolution and large-area laser interference nanomanufacturing technology." Thesis, University of Bedfordshire, 2014. http://hdl.handle.net/10547/576431.
Full textAbstract:
The thesis systematically investigates the laser interference nanomanufacturing technology taking into account its advantages and abilities to realise various potential applications. The latest progresses have addressed the major issues hampering the cross-scale developments of structural applications, such as cost-ineffective fabrication, limited area, low efficiency and challenging integration. The studies carried out on high-resolution and large-area laser interference nanomanufacturing technology will complement the exploration of modern optical devices and extraordinary functional applications. With respect to classical interference theory and relevant references, there is still a lack of studies providing insight into the effects of polarisation on the multi-beam interference while it is found that the polarisation vector plays a key role in the formation, period and contrast of interfering patterns. Herein, the theory of multi-beam interference is developed through the integration of the polarisation vector and electric field vector. It is worth pointing out that based on the detailed analysis of the four-beam interference with the special polarisation modes, it is demonstrated that the modulation phenomenon in four-beam laser interference is the result of the misalignment of incident angles or unequal incident angles only in the case of the TE-TE-TM-TM mode. In the experiments, a straightforward method of generating various well-defined structures on material surfaces is proposed using the nanosecond laser interference system. The experimental results of two-, three- and four-beam interference show a good correspondence to the theoretical analyses and simulations. Artificial bio-structures are fabricated using the four-beam interference method with the TE-TE-TE-TE polarisation mode and the fabricated microcone structures exhibit excellent properties with both a high contact angle (CA=156.3°) and low omnidirectional reflectance (5.9-15.4%). In order to fabricate high-resolution structures, the 266nm nanosecond laser interference system is employed to treat the organic and metal-film materials. Nanograting structures with feature sizes of sub-100nm width and 2nm height are fabricated on the organic material surface. An attempt is successfully conduced to produce the nanoelectrode arrays by using laser interference lithography and chemical deposition. Finally, the advantages of the developed laser interference technology and contributions of the research are summarised, and recommendations of future work are given.
48
Gharbi, Myriam. "Etats de surface de pièces métalliques obtenues en Fabrication Directe par Projection Laser (FDPL) : compréhension physique et voies d’amélioration." Thesis, Paris, ENSAM, 2013. http://www.theses.fr/2013ENAM0026/document.
Full textAbstract:
Le procédé de fabrication directe par projection laser (FDPL), est un procédé de fabrication additive qui permet de fabriquer des pièces de forme complexe directement à partir d'un fichier CAO, sans outil et sans moule. L'un de ses inconvénients majeurs est la mauvaise qualité des états de surface obtenus (Ra supérieur à 15 μm) qui nécessite systématiquement des étapes de ré-usinage. Dans ce contexte, et dans le cadre du projet ANR « ASPECT », cette thèse a pour double objectif une meilleure compréhension de l'origine des états de surface dégradés, et le développement de différentes solutions expérimentales innovantes permettant d'améliorer les états de surface.Dans un premier temps, en considérant des géométries simples (murs) en alliage de titane Ti-6Al-4V, nous avons étudié l'interaction faisceau laser / jet de poudre / bain liquide métallique par différents diagnostics (caméra rapide, caméra thermique, pyrométrie…) pour comprendre l'évolution de la géométrie, la thermique et l'hydrodynamique de la zone fondue (ZF). Ces analyses nous ont permis de corréler les évolutions des ZF à celles des états de surface, et de mettre en évidence, sur le Ti-6Al-4V la prépondérance des effets de tension superficielle sur les effets de gravité, dans l'équilibre des ZF, et l'effet bénéfique de zones fondues larges et profondes combinées à de faibles hauteurs par couche, dans la réduction des micro et macro-rugosités. La réduction du débit massique local Dm* en vis-à-vis des parois latérales et l'augmentation du rayon de courbure des ZF avec l'élargissement des ZF (donc avec des rapports El= P/V (J/m) élevés) sont à l'origine des effets bénéfiques obtenus. Différents modèles analytiques et numériques ont également été utilisés ou développés, en complément des résultats expérimentaux, pour décrire le procédé (modèle d'interaction laser-poudre, modèle numérique thermique 3D du procédé, modèle de calcul des ondulations périodiques).En utilisant un large spectre de conditions expérimentales, et une caractérisation rigoureuse des conditions de fabrication (analyses de faisceau, de jet de poudre …) nous avons également apporté des améliorations notables à la qualité des états de surface obtenus. Ainsi, l'utilisation d'un éclairement laser uniforme plutôt que quasi-Gaussien, ou l'utilisation d'un régime quasi-pulsé plutôt que continu ont permis, sur le Ti-6Al-4V de réduire significativement les gradients thermiques en ZF et les mouvements de convection de Marangoni associés, et d'obtenir des qualités d'états de surface fortement améliorées (Ra< 3 µm) par rapport aux études antérieures sur le sujet.Pour finir, une partie de l'étude s'est concentrée sur l'utilisation d'un autre matériau: l'acier inoxydable 316L, afin d'analyser l'influence de la nature chimique et des propriétés thermo-physiques de la poudre projetée sur la qualité des états de surface. Les résultats ont montré que, contrairement à l'alliage de titane, les meilleures rugosités étaient obtenues pour les énergies linéiques El (J/m) les plus faibles, en raison de la formation, à El élevé, de macro-agglomérats de poudre sur les parois des murs. Ce résultat confirme la difficulté d'une approche prédictive globale des états de surface à partir des paramètres thermo-physiques des matériaux projetésThe process of direct manufacturing by projection laser ( FDPL), is a process of additive manufacturing which allows to make rooms(parts,plays) of complex shape directly from a file CAD, without tool and without mold(mussel). One of its major inconveniences is the bad quality of the states of surface obtained (Ra upper to 15 µm) which requires systematically stages of remanufacturing. In this context, and within the framework of the project ANR " aspect ", this thesis(theory) has for double objective a better understanding of the origin of the degraded states of surface, and the development of various innovative experimental solutions allowing to improve the states of surface. At first, by considering simple geometries (walls) in alloy of titanium Ti-6Al-4V, we studied the interaction
49
Yang, Jr-Syu. "Laser/optical fiber phased array generation of ultrasound for quality control of manufacturing processes." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/17286.
Full text
50
Francis, Zachary Ryan. "The Effects of Laser and Electron Beam Spot Size in Additive Manufacturing Processes." Research Showcase @ CMU, 2017. http://repository.cmu.edu/dissertations/909.
Full textAbstract:
In this work, melt pool size in process mapped in power-velocity space for multiple processes and alloys. In the electron beam wire feed and laser powder feed processes, melt pool dimensions are then related to microstructure in the Ti-6Al-4V alloy. In the electron beam wire feed process, work by previous authors that related prior beta grain size to melt pool area is extended and a control scheme is suggested. In the laser powder feed process, in situ thermal imaging is used to monitor melt pool length. Real time melt pool length measurements are used in feedback control to manipulate the resulting microstructure. In laser and electron beam direct metal additive manufacturing, characteristics of the individual melt pool and the resulting final parts are a product of a variety of process parameters. Laser or electron beam spot size is an important input parameter that can affect the size and shape of a melt pool, and has a direct influence on the formation of lack-of-fusion and keyholing porosity. In this work, models are developed to gain a better understanding of the effects of spot size across different alloys and processes. Models are validated through experiments that also span multiple processes and alloys. Methods to expand the usable processing space are demonstrated in the ProX 200 laser powder bed fusion process. In depth knowledge of process parameters can reduce the occurrence of porosity and flaws throughout processing space and allow for the increased use of non-standard parameter sets. Knowledge of the effects of spot size and other process parameters can enable an operator to expand the usable processing space while avoiding the formation of some types of flaws. Based on simulation and experimental results, regions where potential problems may occur are identified and process parameter based solutions are suggested. Methods to expand the usable processing space are demonstrated in the ProX 200 laser powder bed fusion process. In depth knowledge of process parameters can reduce the occurrence of porosity and flaws throughout processing space and allow for the increased use of non-standard parameter sets.