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1.
Analiza napak pri 3D tiskanju hiš s postopki računalniškega vida
Martin Abram, 2020, undergraduate thesis

Abstract: V okviru tega diplomskega dela smo se ukvarjali z analizo in proučevanjem napak, ki nastanejo v širini betonskih slojev pri 3D tiskanju hiš. Zaradi gostote materiala, vodo-cementnega faktorja, temperature in hitrosti nanašanja materiala se sloji neenakomerno nanašajo drug na drugega. Izdelali smo strojno-programski sistem s katerim izboljšamo natančnost 3D tiskanja. Razvili in implementirali smo algoritem za prepoznavo in analiziranje napak pri 3D tiskanju hiš ter android aplikacijo, ki ta algoritem uporablja. Za prepoznavanje napak smo uporabili tehnike računalniškega vida in se opirali na vizualne informacije, pridobljene s klasičnimi kamerami RGB. Rezultate smo analizirali s pomočjo predpripravljenih posnetkov tiskanja zidu v različnih pogojih. Dobljene rezultate smo primerjali z želeno vrednostjo širine sloja, izmerjena odstopanja pa smo v povratni zanki uporabili za korigiranje 3D tiskanja. Z našo rešitvijo bo gradnja oziroma "tiskanje" hiš kvalitetnejše in hitrejše, saj ne bo nepotrebnih zastojev pri ponovni obdelavi napačno izdelanega zidu. Poraba materiala bo manjša, zid pa bo bolj gladek.
Keywords: 3D tisk, računalniški vid, linijski laser, kamera
Published: 02.11.2020; Views: 75; Downloads: 16
.pdf Full text (2,21 MB)

2.
Snovanje in izdelava laserskega CNC rezalnika
Tomaž Kozmus, 2020, undergraduate thesis

Abstract: Diplomska naloga v prvem delu vsebuje teoretično razlago delovanja laserja, v drugem delu je opisano snovanje laserskega CNC rezalnega stroja, v zadnjem delu pa so predstavljeni rezultati izgradnje tega stroja. S to diplomsko nalogo je bilo dokazano, da je možno izdelati popolnoma delujoč laserski CNC-rezalnik, pri čemer celotni stroški ne presegajo 500 €. Na koncu diplomske naloge je priložena tudi tehniška dokumentacija, ki omogoča ponovitev izdelave tega laserskega CNC-rezalnika.
Keywords: laserski CNC-rezalnik, laser, snovanje izdelka, diodni laser
Published: 24.09.2020; Views: 134; Downloads: 53
.pdf Full text (3,04 MB)

3.
Sistem za lasersko preoblikovanje optičnega vlakna
Dominik Gril, 2019, undergraduate thesis

Abstract: Diplomsko delo opisuje celoten postopek, zasnovo, verifikacijo in preizkušanje sistema za tanjšanje optičnega vlakna na daljših odsekih. V delu je natančno opisana zasnova mehanskih komponent uporabljenih v sistemu, ter njihova naloga in delovanje. Podrobno je opisna programska koda in grafični vmesnik za vodenje celotnega sistema. Vir za segrevanje vlakna v majhni točki je izveden s CO2 laserjem. Posebnost predstavljenega sistema je reguliranje izhodne optične moči CO2 laserja, ki je izvedeno s pomočjo kamere. Predstavljen sistem omogoča izdelavo zožitev optičnih vlaken vse do 10 μm iz različnih začetnih premerov. Prav tako smo prikazali uporabnost sistema za izdelavo krajših kosov posebnih - večjedrnih, brezjedrnih vlaken.
Keywords: zoženje vlakna, CO2 laser, vodenje, mikrokrmilnik, LabVIEW
Published: 25.11.2019; Views: 362; Downloads: 66
.pdf Full text (3,51 MB)

4.
Vpliv izdelovalnih parametrov na lastnosti izdelkov iz Ti-6Al-4V, narejenih s selektivnim laserskim taljenjem in plastenje površine z bioaktivnim polimerom
Snehashis Pal, 2019, doctoral dissertation

Abstract: Technological parameters included in energy density (ED) are the more powerful tools in selective laser melting (SLM) technology which can be used in the time of fabrication to regulate chemical, metallurgical, and mechanical properties of a product. The volumetric Energy Density (ED) depends on the energy input employed by the laser power, scanning speed, hatch spacing, and the layer thickness. Density, microstructure, surface morphology, dimension accuracy, strength and porosity including the number of pores, place of the pore, size of a pore shape of a pore, inclusions of pores of an SLM product depends on the processing parameters. As the powder material fusion process is done by track by track and layer by layer, the architecture of the microstructure in a product is oriented as the direction of building up too. The research has emphasized on metallurgical properties, tensile properties, and producing the non-porous products from Ti-6Al-4V alloy powder and surface modification using bioactive polymer for orthopedic application. The research has followed four steps to study the metallurgical properties and finding out the combinations of technological parameters in producing non-porous products. The purpose of the first step of the study was to examine the effects of ED on the product properties and to obtain an optimum ED as well as the optimal range of scanning speed. The second step of the study has focused on the influences of laser power. The third step of the study has investigated the effect of amounts of track overlapping and hatch spacing. Almost a zero-porosity product has been able to produce by following these three steps of the ongoing research. The fourth step has studied the metallurgical properties emphasizing on re-melting of every layer. High-density products have been found in the fourth step where a small amount of very small sized pores are present as a result of keyhole effect and gaseous bubble entrapment mainly. Four buildup orientations have been selected for each ED in the first step of the study to examine the tensile properties of the products. The best buildup orientation has been seen in longitudinally vertical tensile specimens considering tensile properties. The tensile properties have also been studied in the second and third step of the study with best build up orientation of the tensile specimens. The alterations of metallurgical and tensile properties have also been investigated after heat-treatment of the specific samples. Dimensional accuracies were also invigilated on the cubic, and tensile specimens over the studies and consequently, inaccuracies have been noticed. The fifth step of the study has observed the pore properties, adhesion properties, the compressive strength of gelatin coating manufactured using unidirectional freezing and the freeze-drying process of three different gelatin concentrations on four different surfaced Ti-6Al-4V alloy substrates. The results indicate that the coating properties depend on the substrate’s surface texture as well as the concentration of gelatin. Above 80% of porosity, interconnected and well-aligned pores of 75-200 μm have been obtained which is required to stimulate bone ingrowth histologically.
Keywords: selective laser melting, unidirectional freezing, fabricating parameters, porosity, microstructure, mechanical strength
Published: 01.04.2019; Views: 739; Downloads: 96
.pdf Full text (10,52 MB)

5.
Racionalizacija postopkov izrezovanja pločevine nerjavečih jekel
Daniel Vovk, 2018, undergraduate thesis

Abstract: Želja po uspehu je to, kar vodi do napredka. Kljub temu da je podjetje uspešno, je vedno potrebno premisliti še o dodatni racionalizaciji proizvodnega postopka ter s tem zmanjšati proizvodne stroške, izboljšati kakovost, delovne razmere ter s tem biti na vrhu konkurence. Potrebno je dobro poznavanje proizvodnih postopkov, da lahko oblikujemo optimalni proizvodni proces. V nalogi sem se posvetil različnim rezalnim postopkom. Preučene so bile prednosti in slabosti teh postopkov. Ker prihaja v podjetju do težav pri razrezu nerjavnega jekla, sem podrobno preučil prej omenjeni material ter načine, kako bi te težave odpravili. Po preučenih prednostih in slabostih različnih rezalnih tehnik ter zahtevah po kakovosti je bilo ugotovljeno, da je za podjetje najbolj primeren nakup novega plazemskega rezalnika. Z novo sodobno tehnologijo bi odpravili veliko težav, ki jih povzroča sedanja plazma. Ker v podjetju režemo tudi nerjavna jekla, plamenski rezalnik ni primeren izbor, medtem ko laser ni primeren zaradi razreza tudi debelejših materialov.
Keywords: razrez, plazma, nerjaveče jeklo, laser, plamenski rezalnik, racionalizacija razreza, izboljšanje produktivnosti.
Published: 03.05.2018; Views: 457; Downloads: 111
.pdf Full text (1,91 MB)

6.
Simulating various terrestrial and UAV LiDAR scanning configurations for understory forest structure modelling
Marina Hämmerle, Niko Lukač, K.-C. Chen, Zsófia Koma, C.-K. Wang, K. Anders, B. Höfle, 2017, published scientific conference contribution

Abstract: Information about the 3D structure of understory vegetation is of high relevance in forestry research and management (e.g., for complete biomass estimations). However, it has been hardly investigated systematically with state-of-the-art methods such as static terrestrial laser scanning (TLS) or laser scanning from unmanned aerial vehicle platforms (ULS). A prominent challenge for scanning forests is posed by occlusion, calling for proper TLS scan position or ULS flight line configurations in order to achieve an accurate representation of understory vegetation. The aim of our study is to examine the effect of TLS or ULS scanning strategies on (1) the height of individual understory trees and (2) understory canopy height raster models. We simulate full-waveform TLS and ULS point clouds of a virtual forest plot captured from various combinations of max. 12 TLS scan positions or 3 ULS flight lines. The accuracy of the respective datasets is evaluated with reference values given by the virtually scanned 3D triangle mesh tree models. TLS tree height underestimations range up to 1.84 m (15.30 % of tree height) for single TLS scan positions, but combining three scan positions reduces the underestimation to maximum 0.31 m (2.41 %). Combining ULS flight lines also results in improved tree height representation, with a maximum underestimation of 0.24 m (2.15 %). The presented simulation approach offers a complementary source of information for efficient planning of field campaigns aiming at understory vegetation modelling.
Keywords: forest structure, understory, laser scanning simulation, full waveform, 3D point cloud analysis, field campaign planning
Published: 09.10.2017; Views: 870; Downloads: 287
.pdf Full text (3,71 MB)
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7.
A benchmark of lidar-based single tree detection methods using heterogeneous forest data from the alpine space
Lothar Eysn, Markus Hollaus, Eva Lindberg, Frédéric Berger, Jean-Matthieu Monnet, Michele Dalponte, Milan Kobal, Marco Antonio Pellegrini, Emanuele Lingua, Domen Mongus, Norbert Pfeifer, 2015, original scientific article

Abstract: In this study, eight airborne laser scanning (ALS)-based single tree detection methods are benchmarked and investigated. The methods were applied to a unique dataset originating from different regions of the Alpine Space covering different study areas, forest types, and structures. This is the first benchmark ever performed for different forests within the Alps. The evaluation of the detection results was carried out in a reproducible way by automatically matching them to precise in situ forest inventory data using a restricted nearest neighbor detection approach. Quantitative statistical parameters such as percentages of correctly matched trees and omission and commission errors are presented. The proposed automated matching procedure presented herein shows an overall accuracy of 97%. Method based analysis, investigations per forest type, and an overall benchmark performance are presented. The best matching rate was obtained for single-layered coniferous forests. Dominated trees were challenging for all methods. The overall performance shows a matching rate of 47%, which is comparable to results of other benchmarks performed in the past. The study provides new insight regarding the potential and limits of tree detection with ALS and underlines some key aspects regarding the choice of method when performing single tree detection for the various forest types encountered in alpine regions.
Keywords: single tree extraction, airborne laser scanning, forest inventory, comparative testing, co-registration, mountain forests, Alpine space, matching
Published: 21.06.2017; Views: 468; Downloads: 294
.pdf Full text (13,97 MB)
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8.
The action of a laser on an aluminium target
Višnja Henč-Bartolič, Tonica Bončina, Suzana Jakovljević, Davor Pipić, Franc Zupanič, 2008, original scientific article

Abstract: A nitrogen laser beam (337 nm, 6 ns (FWHM), (3.2 [plus minus] 0.2) mJ) was focused with a quartz lens (f = 100 mm) onto an aluminium target in air at normal pressure. The laser irradiation and plasma explosion caused a modification to the Al surface and the deposition of a thin film (droplets) onto a glassy carbon plate. The irradiated target and the deposited material were studied with a scanning electron microscope (SEM) and a focused-ion-beam (FIB) device. A crater surrounded by a rim was produced on the spot of maximum irradiation on the aluminium target. The crater, very deep in comparison to its width and thickness, was presumably caused by the Kelvin-Helmholtz and the Rayleigh-Taylor instabilities. The temperatures of the electron and the massive particles were explained.
Keywords: aluminium, laser ablation, thin film deposition, instabilities, temperatures
Published: 23.03.2017; Views: 610; Downloads: 70
.pdf Full text (324,07 KB)
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9.
Prediction of the hardness of hardened specimens with a neural network
Matej Babič, Peter Kokol, Igor Belič, Peter Panjan, Miha Kovačič, Jože Balič, Timotej Verbovšek, 2014, original scientific article

Abstract: In this article we describe the methods of intelligent systems to predict the hardness of hardened specimens. We use the mathematical method of fractal geometry in laser techniques. To optimize the structure and properties of tool steel, it is necessary to take into account the effect of the self-organization of a dissipative structure with fractal properties at a load. Fractal material science researches the relation between the parameters of fractal structures and the dissipative properties of tool steel. This paper describes an application of the fractal dimension in the robot laser hardening of specimens. By using fractal dimensions, the changes in the structure can be determined because the fractal dimension is an indicator of the complexity of the sample forms. The tool steel was hardened with different speeds and at different temperatures. The effect of the parameters of robot cells on the material was better understood by researching the fractal dimensions of the microstructures of hardened specimens. With an intelligent system the productivity of the process of laser hardening was increased because the time of the process was decreased and the topographical property of the material was increased.
Keywords: fractal dimension, fractal geometry, neural network, prediction, hardness, steel, tool steel, laser
Published: 17.03.2017; Views: 848; Downloads: 78
.pdf Full text (632,41 KB)
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10.
Influence of the working technology on the development of alloys H13-w(Cu) 87.5 %
Uroš Artiček, Marko Bojinović, Mihael Brunčko, Ivan Anžel, 2014, original scientific article

Abstract: Most dies in the casting industry for injection moulding are machined from the premium-grade H13 tool steel. They provide excellent performance in terms of mechanical properties and service life; however, these dies are characterised by a relatively low thermal conductivity. The tool-and-die industry is interested in depositing a material of a high thermal conductivity onto steel in order to improve the thermal management and productivity. We have explored the possibility of using copper with a new technology. In this study, the microstructure evolution and mechanical properties are discussed using the Laser Engineered Net ShapingTM (LENSTM) technology. For a better understanding of the solidification, the microstructure of a LENS sample was compared with the microstructure of a reference alloy produced with the ingot-casting technology having the same chemical composition of H13-w(Cu) 87.5 %. We carried out light microscopy, scanning electron microscopy, an EDS microchemical analysis, the tensile test and microhardness testing. The results show a successful fabrication of LENS samples; their microstructure is more homogeneous compared to the castings; they show better mechanical properties and represent a good potential for further development and use.
Keywords: casting, laser engineered net shaping technology, microstructure, mechanical properties
Published: 16.03.2017; Views: 720; Downloads: 80
.pdf Full text (3,28 MB)
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