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CNC Engraver : Precision and flexibility of a miniature CNC engraver / CNC Gravyrmaskin : Precision och användningsområden hos småskalig CNC gravyrmaskinBooberg, Rasmus, Borgén, Martin January 2022 (has links)
This report documents the design and construction of a computer-controlled engraver (CNC engraver). Whereas most common machines used for this purpose are dimensioned towards milling, this project aims to create a dedicated engraver which could be of reduced size and complexity in comparison to standard CNC routers. This is partly because engraving imparts no need for a spindle motor, and that the machine only needs to withstand forces related to engraving, which are often significantly smaller than those present when milling. The proposed construction is designed towards use on aluminium and retains about the size of a laptop computer. Additionally, it should allow for engraving on material of almost any size, which is not a common feature in CNC machines. The design uses Arduino and open-source software to generate and execute G-code and is built with off-the-shelf components as well as both 3D-printed and machined components. Key conclusions are that it is indeed possible to make such a machine and that it could fulfil some useful purposes, even if the prototype, as built, has some issues with structural rigidity and therefore the final tolerances of the engraving. These issues primarily stem from the assembly supporting the Z-Axis and engraving bit, which lacks the stiffness needed for desirable results. Taking the fairly low complexity of the build and the price tag of under 2000 SEK in consideration, the prospects are deemed as promising. / Denna rapport beskriver konstruktionen och byggandet av en datorkontrollerad (CNC) gravyrmaskin. Emedan de gängse maskinerna för detta ändamål är en vanlig fräs eller dylikt, så syftar detta projekt att bygga en dedikerad gravyrmaskin, som då jämförelsevis kan vara av reducerad storlek och komplexitet. Maskinen använder Arduino och öppen källkod för att generera och exekvera G-kod, och byggs med inköpta standardkomponenter, såväl som både 3D-printade och egentillverkade komponenter. De främsta slutsatserna är att det mycket riktigt går att bygga en sådan maskin, och det finns användningsområden för en sådan, även om prototypen som den slutligen blev har problem med styvhet, och därför även med noggrannheten i gravyrerna.
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Durabilité tribologique de matériaux pour insert de dents de tunnelier / Increased cutter tools lifetime for tunneling : tribological durability of WC carbide inserts used on TBM's drag bitsMarou Alzouma, Ousseini 16 December 2015 (has links)
La fréquence des opérations de maintenance lors de l’excavation du sol par les tunneliers est problématique pour les entreprises de travaux publics. Ces opérations de maintenance engendrent des temps morts onéreux et nécessitent l'intervention d'opérateurs dans des conditions de travail hyperbares. Une des raisons aux nombreuses interventions humaines pour la maintenance est l’endommagement des outils racleurs du sol excavé (dents) qui sont placés sur la tête du tunnelier. Ces outils sont sujets à l’usure compte tenu de l’abrasivité des différents milieux qu’ils rencontrent. Le but de cette thèse est de contribuer à augmenter d’au moins 20% la durée de vie des matériaux constitutifs de ces outils, afin de réduire les différentes opérations de maintenance qui exposent les opérateurs à des risques importants. Pour atteindre cet objectif, les investigations menées dans ce travail ont porté sur plusieurs axes. Dans un premier temps, une expertise est menée pour identifier les modes d’endommagement prédominants sur les inserts à base de carbure de tungstène placés sur les dents ; ensuite, de nouveaux matériaux avec des propriétés mécaniques et des microstructures optimisées, développés dans le cadre du projet européen NeTTUN, sont caractérisés sur des bancs d’essais représentatifs. Ces essais ont permis de bien comprendre les mécanismes d’usure des nouveaux matériaux à base de carbure de tungstène. Les résultats de ce travail peuvent ensuite donner lieu à de nouvelles orientations en matière de choix de matériaux pour renforcer les dents de tunnelier. / The frequency of maintenance operations during the excavation of the ground by the tunnel boring machines (TBM) is problematic for civil engineering companies. These maintenance operations provoke expensive timeouts and they bring in excavation operators in risky hyperbaric work conditions. One of the reasons which leads to the numerous human interventions for the maintenance is the damage of drag bits located on the cutting wheel of the TBM. These drag bits undergo wear due to the abrasiveness of the various media they meet. The purpose of this thesis is to contribute to increase by 20 % at least the lifetime of the materials of the dag bits, in order to reduce the various maintenance operations which expose the operators to important risks. To achieve this goal, the investigations led in this work concerned several axes. At first, an expertise is led to identify the wear modes prevailing on the carbide inserts located on the drag bits; then, new materials with enhanced mechanical properties and optimized microstructures, developed in the framework of the European project NeTTUN, are characterized on representative lab testing devices. These tests allowed us to understand well the wear mechanisms of the newly developed grades of tungsten carbides. The results of this work can lead to new strategies for the selection of materials to reinforce the drag bits.
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