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.

The aim of this diploma thesis is the design of machine for sheet metal cutting. This machine uses laser beam divide the material. The work is focused on the increase of the aesthetic character the machine has., at the same time the work include an ergonomic improvement, which make the operation more efficient and facile.

The basic acquaintance with laser technology principles. The consideration and evaluation of this technology present state in engineering. The possibilities of applying new knowledge and discoveries in this field for using in engineering. The estimation of laser technology development within further 5 years and consideration of this technology economical demands.

The thesis deals with the technology of laser cutting. The beginning is concerned with a general description of laser technology and laser division into basic groups. Next part refers to possible industrial use of laser beam, especially for cutting. Other chapters deal with the components suitable for the manufacture of this technology, technical preparation of production and the proposal to increase manufacturing flexibility when changing products. The last part is devoted to technical and economic evaluation.

This diploma thesis discusses laser cutting and the consecutive surface treatment of cut parts. The theory of laser cutting is described in the first part of this thesis, including laser history and the laser emergence principle. Cut parameters and the influence of the laser cutting on the material are described later on. The next part describes the laser cutting technological possibilities and other laser technology utilization options are outlined. In the last theory part, metal surface treatment used in the experiment is covered. Coating thickness is evaluated in the practical part of this thesis, as well as roughness, microhardness, chemical microanalysis and metalography. The evaluation of the results achieved, and optimal surface treatment execution suggestions are addressed in the last part of this thesis.

The diploma thesis discusses laser cutting of non-ferrous metals using fiber YbYag laser and evaluation of the roughness of cutting edge samples. To manufacture samples of aluminium Al 99,5, deoxidized copper Cu – DHP and brass CuZn37 were used combinations of process parameters according to Taguchi statistical method. Samples were subsequently evaluated, according to the ČSN EN ISO 9013 standard and sorted into roughness cathegories, and by technical and economical evaluation, the most economical process parameter combinations were found. Experimantal part is preceded by description of general methods of cutting, description of laser types, process parameters and their influence on the occurrence of the cutting edge defects and description of roughness measurement and standard ČSN EN ISO 9013.

This degree work in textile design explores how curtains can be designed to become interactive through textile prints and laser cutting. The work places itself within the field of surface pattern design. The aim was to explore interactive textile prints using perspective as a design variable when designing surface patterns for curtains. The aesthetics of traditional Swedish folk art motifs and colour were an inspiration in the design of the prints. The methods used were a combination of textile transfer printing and laser cutting. The result of this project is a collection of three printed textiles that feature laser cutting and etching in different ways. Through human interaction the textiles can be altered in different ways. It is possible to change the textile and adapt it to seasons, trends and personal preferences. The project aims to offer an alternative approach to sustainable textiles by providing people with possibility to change their interor textiles without needing to consume more products.

A sinterização a laser (SL), uma das tecnologias de manufatura aditiva (MA), se mostra de grande interesse devido a uma série de características, mas, principalmente, devido a sua capacidade de processar uma ampla gama de materiais em pó, a qual amplia possibilidades de pesquisa e desenvolvimento no campo do Design. Neste trabalho, sob o prisma da MA, tem-se por objetivo realizar a sinterização a laser em um equipamento de gravação e corte a laser convencional, sem pré-aquecimento do material. No desenvolvimento do estudo, foi utilizado um equipamento galvanométrico a laser para a realização de experimentos de sinterização de poliestireno em pó (PS 200). Os ensaios de caracterização desse material polimérico amorfo, constataram o diâmetro médio dos grãos de 54,3 μm em formato irregular. Para viabilizar o processo proposto, investigaram-se os parâmetros de processo para a SL, valendo-se de um dispositivo de controle da altura da mesa de trabalho. A melhor amostra (geometria circular) foi construída com potência 20 W, velocidade de varredura de 200 m/min e distância entre linhas de varredura do feixe laser de 0,1 mm. Esse último parâmetro, é relacionado ao diâmetro do foco do feixe laser, o qual foi estimado pelos ensaios em 0,3 mm. Com isso, foi calculada a densidade de energia transferida para o material, conhecida como Número de Andrew (An), em 0,06 J/mm² Análises visuais, macroscópicas e microscópicas, antes e depois da sinterização de uma camada (2D) e de camadas empilhadas (3D), além de sua digitalização tridimensional, foram realizadas. As amostras apresentaram deformação no plano x-y (elipticidade), no eixo z (empenamento) e grande porosidade. Nos ensaios de empilhamento de camadas foi determinada, para os parâmetros utilizados, a espessura de camada de 0,15 mm. Posteriormente, foi construído um modelo 3D com 100 camadas, o qual apresentou um acabamento liso na maior parte de sua lateral, porém, foram observadas estrias verticais ao longo da sua altura, as quais foram consideradas como característica do processo (devido à inércia dos espelhos galvanométricos). Por fim, esses parâmetros foram validados em um ensaio valendo-se de uma forma orgânica (face humana) em escala 1:4. O fator crítico foi o empenamento, o qual prejudica a distribuição de novas camadas de pó, mas pôde ser contornado com espessuras de camada de alturas superiores a esse empenamento. Assim, considera-se que para a viabilização prática do processo de sinterização proposto, em equipamentos de corte e gravação a laser convencionais, torna-se importante o desenvolvimento de um dispositivo de distribuição de pó automatizado, o qual permitiria a construção de modelos 3D de maior tamanho e complexidade. / Laser sintering (SL), one of the additive manufacturing (MA) technologies, is of great interest due to a number of characteristics, but mainly due to its ability to process a wide range of powder materials, which offers possibilities for research and development in the Design’s field. In this work, under the prism of the MA, the goal is to perform laser sintering in a conventional laser engraving and cutting equipment, without preheating the material. In the development of the study, a galvanometric laser equipment was used to perform powder polystyrene (PS 200) sintering experiments. The characterization tests of this amorphous polymer material showed the average grain diameter of 54.3 μm in irregular shape. In order to make the proposed process feasible, the process parameters for the SL were investigated, using a device to control the height of the workbench. The best sample (circular geometry) was built with 20 W power, laser scan speed of 200 m/min and distance between scanned lines of 0.1 mm. This last parameter is related to the diameter of the laser beam waist, which was estimated by the tests in 0.3 mm Thus, the energy density transferred to the material, known as Andrew's Number (An), was calculated at 0.06 J/mm². Macroscopic and microscopic visual analysis, before and after the sintering of a two-dimensional layer (2D) and of stacked layers (3D), in addition to its 3D scanning, were performed. The samples displayed deformation in the x-y plane (ellipticity), at the z-axis (warpage) and high porosity. In the layer stacking tests, the layer thickness of 0.15 mm was determined for the parameters used. Next, a 3D model with 100 layers was sintered, which presented a smooth finish in most of its lateral, however, vertical streaks were observed along its height, which were considered as characteristic of the process (due to the inertia of the galvanometric mirrors). Finally, these parameters were validated in an assay using an organic form (human face) in a 1: 4 scale. The critical factor was the warpage, which impairs the distribution of new layers of powder, but could be worked around with layer thicknesses of heights higher than this warpage. Thus, it is considered that for the practical feasibility of the proposed sintering process in conventional laser cutting and engraving machine, it is important to develop an automated powder distribution device, which would allow the construction of greater size and complexity 3D models.

A sinterização a laser (SL), uma das tecnologias de manufatura aditiva (MA), se mostra de grande interesse devido a uma série de características, mas, principalmente, devido a sua capacidade de processar uma ampla gama de materiais em pó, a qual amplia possibilidades de pesquisa e desenvolvimento no campo do Design. Neste trabalho, sob o prisma da MA, tem-se por objetivo realizar a sinterização a laser em um equipamento de gravação e corte a laser convencional, sem pré-aquecimento do material. No desenvolvimento do estudo, foi utilizado um equipamento galvanométrico a laser para a realização de experimentos de sinterização de poliestireno em pó (PS 200). Os ensaios de caracterização desse material polimérico amorfo, constataram o diâmetro médio dos grãos de 54,3 μm em formato irregular. Para viabilizar o processo proposto, investigaram-se os parâmetros de processo para a SL, valendo-se de um dispositivo de controle da altura da mesa de trabalho. A melhor amostra (geometria circular) foi construída com potência 20 W, velocidade de varredura de 200 m/min e distância entre linhas de varredura do feixe laser de 0,1 mm. Esse último parâmetro, é relacionado ao diâmetro do foco do feixe laser, o qual foi estimado pelos ensaios em 0,3 mm. Com isso, foi calculada a densidade de energia transferida para o material, conhecida como Número de Andrew (An), em 0,06 J/mm² Análises visuais, macroscópicas e microscópicas, antes e depois da sinterização de uma camada (2D) e de camadas empilhadas (3D), além de sua digitalização tridimensional, foram realizadas. As amostras apresentaram deformação no plano x-y (elipticidade), no eixo z (empenamento) e grande porosidade. Nos ensaios de empilhamento de camadas foi determinada, para os parâmetros utilizados, a espessura de camada de 0,15 mm. Posteriormente, foi construído um modelo 3D com 100 camadas, o qual apresentou um acabamento liso na maior parte de sua lateral, porém, foram observadas estrias verticais ao longo da sua altura, as quais foram consideradas como característica do processo (devido à inércia dos espelhos galvanométricos). Por fim, esses parâmetros foram validados em um ensaio valendo-se de uma forma orgânica (face humana) em escala 1:4. O fator crítico foi o empenamento, o qual prejudica a distribuição de novas camadas de pó, mas pôde ser contornado com espessuras de camada de alturas superiores a esse empenamento. Assim, considera-se que para a viabilização prática do processo de sinterização proposto, em equipamentos de corte e gravação a laser convencionais, torna-se importante o desenvolvimento de um dispositivo de distribuição de pó automatizado, o qual permitiria a construção de modelos 3D de maior tamanho e complexidade. / Laser sintering (SL), one of the additive manufacturing (MA) technologies, is of great interest due to a number of characteristics, but mainly due to its ability to process a wide range of powder materials, which offers possibilities for research and development in the Design’s field. In this work, under the prism of the MA, the goal is to perform laser sintering in a conventional laser engraving and cutting equipment, without preheating the material. In the development of the study, a galvanometric laser equipment was used to perform powder polystyrene (PS 200) sintering experiments. The characterization tests of this amorphous polymer material showed the average grain diameter of 54.3 μm in irregular shape. In order to make the proposed process feasible, the process parameters for the SL were investigated, using a device to control the height of the workbench. The best sample (circular geometry) was built with 20 W power, laser scan speed of 200 m/min and distance between scanned lines of 0.1 mm. This last parameter is related to the diameter of the laser beam waist, which was estimated by the tests in 0.3 mm Thus, the energy density transferred to the material, known as Andrew's Number (An), was calculated at 0.06 J/mm². Macroscopic and microscopic visual analysis, before and after the sintering of a two-dimensional layer (2D) and of stacked layers (3D), in addition to its 3D scanning, were performed. The samples displayed deformation in the x-y plane (ellipticity), at the z-axis (warpage) and high porosity. In the layer stacking tests, the layer thickness of 0.15 mm was determined for the parameters used. Next, a 3D model with 100 layers was sintered, which presented a smooth finish in most of its lateral, however, vertical streaks were observed along its height, which were considered as characteristic of the process (due to the inertia of the galvanometric mirrors). Finally, these parameters were validated in an assay using an organic form (human face) in a 1: 4 scale. The critical factor was the warpage, which impairs the distribution of new layers of powder, but could be worked around with layer thicknesses of heights higher than this warpage. Thus, it is considered that for the practical feasibility of the proposed sintering process in conventional laser cutting and engraving machine, it is important to develop an automated powder distribution device, which would allow the construction of greater size and complexity 3D models.

This thesis concerns experimental investigations of laser cutting and piercing, with theoretical and practical discussions of the results. The thesis is made up of an introduction to laser cutting and six scientific Papers. These Papers are linked in such a way that each of them studies a different aspect of laser cutting: process efficiency in Paper I, morphology and melt flow on the laser cut front in Papers II, III and IV and laser piercing in Papers V and VI. Paper I investigates 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 CO2 and fibre laser 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. In Paper II a new experimental technique is presented which has been developed to enable 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. Paper III presents numerical simulations of the melt flow on a fibre laser ablation-driven processing front during remote fusion cutting, RFC. The simulations were validated with high speed imaging observations of the processing front. The simulation results provide explanations of the main liquid transport mechanisms on the processing front, based on information on the temperature, velocity and pressure fields involved. The results are of fundamental relevance for any process governed by a laser ablation induced front. In Paper IV cutting fronts created by CO2 and fibre lasers in stainless steel at thicknesses between 2 mm and 10 mm have been ‘frozen’ and their geometry has been measured. The resulting three-dimensional shapes have been curve fitted as ninth order polynomials. Various features of the cutting front geometry are discussed, including the lack of correlation of the cut front inclination with either the relevant Brewster angle or the inclination of the striations on the cut edge. In this paper, mathematical descriptions of the cutting fronts are obtained, which can be used as input parameters by any researcher in the field of laser cutting simulations. Paper V investigates the subject of laser piercing. Before any cut is started the laser needs to pierce the material. In this paper the laser piercing process is investigated using a wide range of laser pulse parameters, for stainless steel using a fibre laser. The results reveal the influence of pulse parameters on pierce time and pierced hole diameter. A high speed imaging camera was used to time the penetration event and to study the laser-material interactions involved in drilling the pierced holes. In Paper VI a ‘dynamic’ or ‘moving beam’, laser piercing technique is introduced for processing 15 mm thick stainless steel. One important aspect of laser piercing is the reliability of the process because industrial laser cutting machines are programmed for the minimum reliable pierce time. In this work a comparison was made between a stationary laser and a laser which moves along a circular trajectory with varying processing speeds. High speed imaging was employed during the piercing process to understand melt behavior inside the pierce hole. Throughout this work experimental techniques, including advanced high speed imaging, have been used in conjunction with simulations and theoretical analysis, to provide new knowledge for understanding and improving laser beam cutting and its associated piercing process.