Master thesis deals with topic about 3D printers, concretely making hardware of control and power electronic for FDM 3D printer. The work could offer an overview about basic 3D printing technologies after reading. More information could be read about FDM technology, which is used in our printer, also with description of all important components. The furthest is discussed about electronic drives. If reader is interested in this topic, part of this thesis is schematic design of control electronics, which can be used to build own boards. Design of printed circuit boards is not present in attachment and can be obtained by contacting the author. For own control is used one of the open source control software. Mechanical problems and also mechanical design is done in parallel thesis by other student of Faculty of mechanical engineering.

Den additiva tillverkningsindustrin associeras ofta med en hållbar hushållning av resurser. Trots detta har denna industriavfall med stor potential till vidare användning. Detta kandidatexamensarbete undersöker möjligheten att använda Polyamid 12 (PA12) avfall från selektiv lasersintring (SLS) i formen av filament till en annan additiv tillverkningsmetod, friformsframställning. Avfall från olika delar av SLS-processen försågs av life science företaget Cytiva. Olika blandningar av avfallen extruderades till filament. Innan extrudering undersöktes innehåll samt de termiska egenskaperna hos avfallet med hjälp av differentiell skanningskalometri (DSC), termogravimetrisk analys och fourier transform infraröd spektroskopi. Filamenten analyserades med dragprovning, DSC och svepelektronmikroskopi. Rent obearbetat PA12 pulver och ett kommersiellt PA12 filament användes som referenser vid jämförelse. Blandningarna innehållande avfall från SLS-printerns automatiska rengöringsprocess var kontaminerade med glaspartiklar och blev därför spröda och erhöll en skrovlig yta. Dessa filament gick inte att 3D-printa eftersom glaspartiklar ansamlades i munstycket av printern. Flera filament fick en ojäm och liten diameter och kunde därför inte användas i 3D-printern. Ojämn och liten diameter blev resultatet av bekymmer med sensorn som mäter diametern av filamenten. Dessa filament gjordes av granulerade utskrivna prototyper, pulver nära utskrivna delar och silat pulver långt ifrån de utskrivna delarna. Filament gjorda på blandningar innehållande avfall från dammsugaren som används för att rengöra SLS-printern kunde med framgång skrivas ut i 3D-printern. Dessa filament hade en jämn diameter och innehöll inga större kontamineringar. Det är därför genomförbart att tillverka filament av avfall från alla delar av SLS-processen även om inte alla filament kunde 3D-printas. / Additive manufacturing is often associated with sustainable use of resources. However, this industry still has material waste with great potential for further use. This bachelor thesis examines the opportunity of using Polyamide 12 (PA12) waste from Selective laser sintering (SLS) in the form of filaments for another additive manufacturing method, fused filament fabrication. Waste from different parts of the SLS process were provided from the life science company Cytiva. Several blends of the waste were made into filaments. Prior extrusion, the thermal properties and content of the waste were examined with differential scanning calorimetry (DSC), thermogravimetric analysis and fourier transform infrared spectroscopy. The filaments were analyzed by tensile testing, DSC and scanning electron microscopy. Pure virgin powder of PA12 and a commercial PA12 filament were used as a reference for comparison. The blends containing waste from the SLS printer’s automatic blasting was contaminated with glass beads which resulted in brittle filaments with a rough surface. These filaments were not possible to 3D print with due to accumulation of glass beads in the nozzle of the printer. Several filaments got an uneven and small diameter and could therefore not be 3D printed with. The small and uneven diameter was a result of issues with the sensor measuring the diameter. This includes filaments made of granulated printed prototypes, powder close to the printed parts and sieved powder further away from printed parts. The filaments made of blends including waste from the vacuum cleaner used to clean the SLS printer could successfully be used in printing. These filaments had an even diameter and did not contain any larger contaminations. It is therefore possible to make filaments from waste from all parts of the SLS process although not all filaments could be 3D printed.

This thesis presents a model for the procedures of manufacturing Fused Fila ment Fabrication (FFF) components by calculating required process parameters using empirical equations. Such an empirical model has been required within the FFF field of research for a considerable amount of time and will allow for an ex pansion in understanding of the fundamental mathematics of FFF. Data acquired through experimentation has allowed for a data set of geometric characteristics to be built up and used to validate the model presented. The research presented draws on previous literature in the fields of additive manufacturing, machine engi neering, tool-path programming, polymer science and rheology. Combining these research fields has allowed for an understanding of the FFF process which has been presented in its simplest form allowing FFF users of all levels to incorporate the empirical model into their work whilst still allowing for the complexity of the process. Initial literature research showed that Polylactic Acid (PLA) is now in common use within the field of FFF and therefore was selected as the main working mate rial for this project. The FFF technique, which combines extrusion and Computer Aided Manufacturing (CAM) techniques, has a relatively recent history with lit tle understood about the fundamental mathematics governing the process. This project aims to rectify the apparent gap in understanding and create a basis upon which to build research for understanding complex FFF techniques and/or pro cesses involving extruding polymer onto surfaces.

In this bachelor thesis, I examine how automation of fused filament fabrication (FFF) can be implemented, and what the limitations are for different kinds of automation solutions for FFF. Fused filament fabrication is a 3D-printing technology where a material is extruded through a nozzle, layer by layer, to create a print. The thesis also provides a calculation for the commercial feasibility of small batch rapid production with the implementation of an automation solution for FFF. The approach was a qualitative study containing five interviews, combined with empirical knowledge and data from the additive manufacturing company Svensson 3D. This was complemented with an analysis of which criteria to use when evaluating FFF automation solutions, and a framework for looking at FFF from an operator perspective. To calculate commercial feasibility of automation solutions for FFF, Internal Rate of Return and Payback Time were used. This resulted in six criteria to evaluate solutions for automation of FFF, three evaluations of problems within three solutions for automation of FFF, and a finding showing that small batch rapid production is commercially feasible with automated FFF. Lastly, the thesis contains a discussion regarding what the future is for FFF, and the limitations of the framework presented for evaluating automated FFF systems. Possible promising solutions for automated FFF are presented, together with ideas for how design for additive manufacturing can help shape the future of automated FFF. / I det här kandidatarbetet undersöker jag hur automatisering inom fused filament fabrication (FFF) kan implementeras, och vad begränsningarna är för olika sorters automatiseringslösningar för FFF. Det läggs även fram en uträkning för den kommersiella gångbarheten för small batch rapid production med implementeringen av ett automatiskt FFF-system. Tillvägagångsättet bestod av en kvalitativ studie baserad på fem intervjuer, kombinerad med empirisk kunskap och data från additiva tillverkningsföretaget Svensson 3D. Det här kompletterades med en analys av vilka parametrar som bör användas för att utvärdera lösningar för FFF-automatisering, och ett ramverk där automatiseringslösningarna betraktas ur ett operatörs-perspektiv. För att räkna ut den kommersiella gångbarheten för automatiseringslösningar av FFF användes internränta och återbetalningstid. Det här resulterade i sex parametrar för att utvärdera automatiseringslösningar för FFF, tre utvärderingar av vilka problem som finns i tre existerande automatiseringslösningar, och slutsatsen att small batch rapid production är kommersiellt gångbart för automatiserad FFF. Slutligen innehåller arbetet en diskussion gällande framtiden för FFF och begränsningarna hos det ramverk som presenterades för att utvärdera automatiserade FFF system. Möjliga lovande lösningar för automatiserad FFF presenteras och hur design för additiv tillverkning kan hjälpa till att forma framtiden för automatiserad FFF.

This diploma thesis deals with the solution 3D printing by KUKA robotic arm without realization of supporting structures. The 6-axis KUKA KR 60HA robotic arm allows adjusting 3D printing strategies compared to classical 3D printing concept. The first part of the diploma thesis is about the identification of the current state of knowledge, especially the state of the experimental device for the robotic 3D print. To improve quality of the printed is necessary to modify the printing head and develop the suitable calibration principle. Special printing strategies were designed to rearch the 3D printing overhead volumes without creating support structure. A special alghoritm in the Grasshopper evnironment was developed for generating 3D print trajectory on the body surface. For the quality improvement it is necessary to optimize the process parameters. The final step is experimental 3D printing with the evaluation of surface dimensions, geometric precision and layer coherence in various printing strategies.

No description available.

O objetivo deste estudo foi o desenvolvimento de compósitos poliméricos flexíveis e altamente condutores elétricos preparados por moldagem por compressão e por fabricação de filamentos fundidos (FFF) para possíveis aplicações como materiais piezoresistivos ou piezoelétricos para sensores de compressão. Compósitos baseados em misturas de poli(fluoreto de vinilideno)/poliuretano termoplástico (PVDF/TPU) como matriz e contendo várias frações de negro de fumo-polipirrol (CB-PPy) como aditivo condutor foram preparados. Diversas técnicas de caracterização foram realizadas para avaliar as propriedades mecânicas, térmicas, químicas e elétricas, morfologia e printabilidade dos materiais investigados. Primeiro, blendas de PVDF/TPU com diferentes composições foram produzidas por mistura por fusão seguida de moldagem por compressão. Os resultados mostraram que a flexibilidade desejada para os materiais foi melhorada com a adição de TPU aos compósitos de PVDF. As imagens SEM evidenciaram a obtenção de uma blenda co-contínua com 50/50 vol% de PVDF/TPU. As blendas compostas de PVDF/TPU 38/62 vol% e a blenda co-contínua de PVDF/TPU 50/50 vol% foram selecionadas como matrizes para a preparação de compósitos moldados por compressão e impressos em 3D a fim de alcançar uma ótima combinação entre condutividade, propriedades mecânicas e printabilidade. Várias quantidades de negro de fumo-polipirrol, de 0 a 15%, foram adicionadas às blendas selecionadas para aumentar a condutividade elétrica dos compósitos e possivelmente atuar como agente nucleante para a fase cristalina do PVDF a fim de aumentar sua resposta piezoelétrica. A adição de CB-PPy aumentou a condutividade elétrica de todos os compósitos. No entanto, a condutividade elétrica dos compósitos baseados em blendas co-contínuas PVDF/TPU 50/50 vol% foi maior do que as encontradas para os compósitos de PVDF/TPU 38/62 vol% com mesma concentração de aditivo. De fato, o limiar de percolação elétrico dos compósitos com blenda co-contínua foi de 2%, enquanto o limiar de percolação elétrico dos compósitos compostos da blenda não contínua foi de 5%. Com relação às propriedades mecânicas, a incorporação do aditivo condutor nas blendas resultou em materiais mais rígidos com maior módulo de elasticidade, menor alongamento na ruptura e maior módulo de armazenamento. O módulo de armazenamento (G') e a viscosidade complexa (η*) dos compósitos aumentaram com a adição de CB-PPy. O limiar de percolação reológico foi de 3% para PVDF/TPU/CB-PPy 38/62 vol% e 1% para PVDF/TPU/CB-PPy 50/50 vol%, indicando que uma quantidade maior de carga poderia comprometer a processabilidade dos compósitos. A adição de CB-PPy também resultou na redução dos valores de Tg e Tm dos compósitos devido à redução da mobilidade das cadeias poliméricas. Com base na condutividade elétrica e no comportamento mecânico dos compósitos, três composições diferentes foram selecionadas para a extrusão de filamentos para serem posteriormente utilizados no processo de impressão 3D. No geral, as peças impressas em 3D apresentaram propriedades mecânicas e elétricas inferiores devido à presença de vazios, defeitos e camadas sobrepostas que podem dificultar o fluxo de elétrons. Os valores de condutividade elétrica dos compósitos impressos em 3D de PVDF/TPU/CB-PPy 38/62 vol% contendo 5% e 6% de CB-PPy são de uma a sete ordens de grandeza menores do que os encontrados para os compósitos com a mesma composição moldados por compressão. Mesmo que o valor da condutividade elétrica para o compósito PVDF/TPU 38/62 vol% com 6% de CB-PPy moldado por compressão foi de 1,94x10-1 S•m-1, o compósito impresso em 3D com a mesma composição mostrou um valor muito baixo de condutividade elétrica de 6,01x10-8 S•m-1. Por outro lado, o compósito co-contínuo de PVDF/TPU 50/50 vol% com 10% de aditivo impresso em 3D apresentou um alto valor de condutividade elétrica de 4,14×100 S•m-1 mesmo após o processo de impressão. Além disso, as respostas piezoresistivas dos compósitos foram investigadas. Para os compósitos PVDF/TPU/CB-PPy 38/62 vol%, as amostras moldadas por compressão e impressas em 3D com 5% e 6% de CB-PPy exibiram boa resposta piezoresistiva. No entanto, apenas os compósitos com 6% de aditivo apresentaram valores elevados de sensibilidade e gauge factor, atuação em ampla faixa de pressão e respostas piezoresistivas reprodutíveis durante a aplicação de 100 ciclos de compressão/descompressão para ambos os métodos de fabricação. Por outro lado, para os compósitos co-contínuos de PVDF/TPU/CB-PPy apenas a amostra moldada por compressão com 5% de CB-PPy apresentou respostas piezorresistivas boas e reprodutíveis. A cristalinidade e o teor de fase β do PVDF foram investigados para os compósitos. Embora o grau de cristalinidade das amostras tenha diminuído com a adição de CB-PPy, a porcentagem de fase β no PVDF aumentou. O coeficiente piezoelétrico d33 das amostras aumentou com a porcentagem de fase β. A adição de 6% ou mais de CB-PPy foi necessária para aumentar significativamente o coeficiente piezoelétrico (d33) dos compósitos. O conteúdo de fase β e as respostas piezoelétricas do PVDF foram menores para as amostras preparadas por FFF. Por fim, como pesquisa colateral, a eficiência de blindagem contra interferência eletromagnética (EMI-SE) foi medida para todos os compósitos. Compósitos com maior condutividade elétrica apresentaram melhor blindagem da radiação eletromagnética. Além disso, os compósitos baseados na blenda co-contínua apresentaram maior eficiência de blindagem contra EMI do que os compósitos de PVDF/TPU 38/62 vol%. O principal mecanismo de blindagem foi a absorção para todos os compósitos. As amostras preparadas por FFF apresentaram respostas de EMI-SE menores quando comparadas às amostras moldadas por compressão. / The aim of this study was the development of flexible and highly electrically conductive polymer composites via compression molding and fused filament fabrication for possible applications as piezoresistive or piezoelectric materials for pressure sensors. Composites based on blends of poly(vinylidene fluoride)/thermoplastic polyurethane (PVDF/TPU) as matrix and containing various fractions of carbon black-polypyrrole (CB-PPy) as conductive filler were prepared. Several characterization techniques were performed in order to evaluate the mechanical, thermal, chemical and electrical properties, morphology and printability of the investigated materials. First, PVDF/TPU blends with different compositions were prepared by melt compounding followed by compression molding. The results showed that the flexibility aimed for the final materials was improved with the addition of TPU to PVDF composites. SEM images evidenced the achievement of a co-continuous blend comprising 50/50 vol% of PVDF/TPU. The blends composed of PVDF/TPU 38/62 vol% and the co-continuous blend of PVDF/TPU 50/50 vol% were selected as matrices for the preparation of compression molded and 3D printed composites in order to achieve an optimal compromise between electrical conductivity, mechanical properties and printability. Various amounts of carbon black-polypyrrole, from 0 up to 15%, were added to the selected blends in order to rise the electrical conductivity of the composites and to possible act as nucleating filler for the β crystalline phase of PVDF in order to increase its piezoelectric response. The addition of CB-PPy increased the electrical conductivity of all composites. However, the electrical conductivity of composites based on PVDF/TPU 50/50 vol% co-continuous blends was higher than those found for PVDF/TPU 38/62 vol% composites at the same filler content. Indeed, the electrical percolation threshold of the conductive co-continuous composite blends was 2%, while the electrical percolation threshold of the composites with the nonco-continuous composite blends was 5%. With respect to the mechanical properties, the incorporation of the filler into the blends leaded to more rigid materials with higher elastic modulus, lower elongation at break and higher storage modulus. The storage modulus (G’) and complex viscosity (η*) of the composites increased with the addition of CB-PPy. The rheological percolation threshold was found to be 3% for PVDF/TPU/CB-PPy 38/62 vol% and 1% for PVDF/TPU/CB-PPy 50/50 vol%, indicating that higher amount of filler could compromise the processability of the composites. The addition of CB-PPy also resulted in a reduction on the Tg and Tm values of the composites due to the reduction of the mobility of the polymeric chains. Based on the electrical conductivity and mechanical behavior of the composites, three different compositions were selected for the extrusion of filaments to be used in a 3D printing process. Overall, the 3D printed parts presented lower mechanical and electrical properties because of the presence of voids, defects and overlapping layers that can hinder the flow of electrons. The electrical conductivity values of PVDF/TPU/CB-PPy 38/62 vol% composites containing 5% and 6 wt% of CB-PPy 3D printed samples are one to seven orders of magnitude lower than those found for compression molded composites with the same composition. Even if the electrical conductivity value for PVDF/TPU 38/62 vol% compression molded composite with 6% of CB-PPy was as high as 1.94x10-1 S•m-1, the 3D printed composite with same composition showed a very low electrical conductivity of 6.01x10-8 S•m-1. On the other hand, the 3D printed co-continuous composite PVDF/TPU 50/50 vol% with 10% of filler displayed a high value of electrical conductivity of 4.14×100 S•m-1 even after the printing process. Moreover, the piezoresistive responses of the composites were investigated. For PVDF/TPU/CB-PPy 38/62 vol% composites, the compression molded and 3D printed samples with 5% and 6% of CB-PPy exhibited good piezoresistive response. However, only the composites with 6% displayed high sensitivity and gauge factor values, large pressure range and reproducible piezoresistive responses under 100 cycles for both methods. On the other hand, for PVDF/TPU/CB-PPy co-continuous composites only the compression molded sample with 5% of CB-PPy presented good and reproducible piezoresistive responses. The crystallinity and β phase content of PVDF were investigated for the composites. Althought the degree of crystallinity of the samples decreased with the addition of CB-PPy, the percentage of β phase in PVDF was increased. The piezoelectric coefficient d33 of the samples increased with the percentage of β phase. The addition of 6% or more of CB-PPy was necessary to increase significatively the piezoelectric coefficient (d33) of the composites. The β phase content and piezoelectric responses of PVDF were lower for samples prepared by FFF. Finally, as a collateral research, the electromagnetic interference shielding effectiveness (EMI-SE) were measured for all composites. Composites with higher electrical conductivity showed better shielding of the electromagnetic radiation. In addition, composites based on the co-continuous blend displayed higher EMI shielding efficiency than 38/62 vol% composites. The main mechanism of shielding was absorption for all composites. Specimens prepared by FFF displayed diminished EMI-SE responses when compared to compression molded samples. / Lo scopo di questo studio è lo sviluppo di compositi polimerici flessibili e ad elevata conducibilità elettrica tramite stampaggio a compressione e manifattura additiva (fused filament fabrication) per possibili applicazioni come materiali piezoresistivi o piezoelettrici in sensori di pressione. In particolare, sono stati preparati compositi a base di miscele di poli(vinilidene fluoruro)/poliuretano termoplastico (PVDF/TPU) come matrice e contenenti varie frazioni di nerofumo-polipirrolo (CB-PPy) come riempitivo conduttivo. Sono state utilizzate diverse tecniche di caratterizzazione al fine di valutare le proprietà meccaniche, termiche, chimiche ed elettriche, la morfologia e la stampabilità dei materiali ottenuti. In primo luogo, miscele PVDF/TPU con diverse composizioni sono state preparate mediante mescolatura allo stato fuso seguita da stampaggio a compressione. I risultati hanno mostrato che la flessibilità del PVDF viene notevolemente migliorata dall’aggiunta di TPU. Le immagini SEM hanno evidenziato il raggiungimento di una miscela co-continua per una composizione 50/50% in volume di PVDF/TPU. Le miscele composte da PVDF/TPU 38/62 vol% e la miscela co-continua di PVDF/TPU 50/50 vol% sono state selezionate come matrici per la preparazione di compositi per stampaggio a compressione e manifattura additiva al fine di ottenere un compromesso ottimale tra conducibilità, proprietà meccaniche e stampabilità. Alle miscele selezionate sono state aggiunte varie quantità di nerofumo-polipirrolo, dallo 0 al 15%, per aumentare la conducibilità elettrica dei compositi ed eventualmente fungere da additivo nucleante per la fase β cristallina del PVDF al fine di aumentarne la risposta piezoelettrica. L'aggiunta di CB-PPy ha aumentato la conduttività elettrica di tutti i compositi. Tuttavia, la conduttività elettrica dei compositi basati su miscele co-continue di PVDF/TPU 50/50% in volume era superiore a quella trovata per compositi PVDF/TPU 38/62% in volume con lo stesso contenuto di riempitivo. Infatti, la soglia di percolazione elettrica delle miscele conduttive era del 2%, mentre la soglia di percolazione elettrica dei compositi con miscele composite non continue era del 5%. Per quanto riguarda le proprietà meccaniche, l'incorporazione del riempitivo nelle mescole ha portato a materiali più rigidi con modulo elastico più elevato, allungamento a rottura inferiore e modulo conservativo più elevato. Il modulo conservativo (G') e la viscosità complessa (η*) dei compositi sono aumentate con l'aggiunta di CB-PPy. La soglia di percolazione reologica è risultata essere del 3% per PVDF/TPU/CB-PPy 38/62 vol% e dell'1% per PVDF/TPU/CB-PPy 50/50 vol%, indicando che una maggiore quantità di riempitivo potrebbe compromettere la processabilità dei compositi. L'aggiunta di CB-PPy ha comportato anche una riduzione dei valori di Tg e Tm dei compositi a causa della riduzione della mobilità delle catene polimeriche. Sulla base della conduttività elettrica e del comportamento meccanico dei compositi, sono state selezionate tre diverse composizioni per l'estrusione di filamenti da utilizzare in un processo di stampa 3D. Nel complesso, le parti stampate in 3D presentavano proprietà meccaniche ed elettriche inferiori a causa della presenza di vuoti, difetti e strati sovrapposti che possono ostacolare il flusso di elettroni. I valori di conducibilità elettrica dei compositi PVDF/TPU/CB-PPy 38/62 vol% contenenti il 5% e il 6% di CB-PPy di campioni stampati in 3D sono da uno a sette ordini di grandezza inferiori a quelli trovati per i compositi stampati a compressione con la stessa composizione. Anche se il valore di conducibilità elettrica per il composito stampato a compressione PVDF/TPU 38/62 vol% con il 6% di CB-PPy era pari a 1,94x10-1 S•m-1, il composito stampato in 3D con la stessa composizione ha mostrato un valore molto basso di conducibilità elettrica, pari a 6,01x10-8 S•m-1. D'altra parte, il composito PVDF/TPU 50/50 vol% stampato in 3D con il 10% di riempitivo ha mostrato un elevato valore di conducibilità elettrica, pari a 4,14 × 100 S•m-1, anche dopo il processo di stampa. Inoltre, sono state studiate le risposte piezoresistive dei compositi. Per i compositi PVDF/TPU/CB-PPy 38/62 vol%, i campioni stampati a compressione e stampati in 3D con il 5% e il 6% di CB-PPy hanno mostrato una buona risposta piezoresistiva. Tuttavia, solo i compositi con il 6% hanno mostrato valori di sensibilità e gauge factor elevati, ampio intervallo di pressione e risposte piezoresistive riproducibili in 100 cicli per entrambi i metodi. D'altra parte, per i compositi co-continui PVDF/TPU/CB-PPy solo il campione stampato a compressione con il 5% di CB-PPy ha presentato risposte piezoresistive adeguate e riproducibili. La cristallinità e il contenuto di fase β del PVDF sono stati studiati per i compositi. Sebbene il grado di cristallinità dei campioni diminuisca con l'aggiunta di CB-PPy, la percentuale di fase β in PVDF risulta aumentata. Il coefficiente piezoelettrico d33 dei campioni aumenta anch’esso con la percentuale di fase β. L'aggiunta del 6% o più di CB-PPy è stata necessaria per aumentare significativamente il coefficiente piezoelettrico (d33) dei compositi. Il contenuto di fase β e le risposte piezoelettriche del PVDF sono inferiori per i campioni ottenuti mediante stampa 3D. Infine, come ricerca collaterale, è stata misurata l'efficacia della schermatura contro le interferenze elettromagnetiche (EMI-SE) per tutti i compositi. I compositi con una maggiore conduttività elettrica hanno mostrato una migliore schermatura della radiazione elettromagnetica. Inoltre, i compositi basati sulla miscela co-continua hanno mostrato un'efficienza di schermatura EMI maggiore rispetto ai compositi a 38/62% in volume. Per tutti i compositi, il principale meccanismo di schermatura è l'assorbimento. I campioni preparati mediante manifattura additiva hanno mostrato risposte EMI-SE inferiori rispetto ai campioni stampati a compressione.

Seit Jahren muss sich die Jugend vorwerfen lassen, politikverdrossen zu sein. Spätestens seit Beginn des Jahres 2019 ist dieses Pauschalurteil nur noch schwer zu verteidigen. Denn jeden Freitag gehen deutschlandweit tausende junge Menschen auf die Straßen und machen lautstark auf ihre Anliegen aufmerksam. Inspiriert durch die junge Schwedin Greta Thunberg, die im August 2018 einen einsamen Protest startete, entwickelt sich in kurzer Zeit eine globale Bewegung, die für das ureigenste Interesse der Jugend eintritt: Für die eigene Zukunft. Die Fridays-for-Future-Bewegung drängt mit weltweit hunderttausenden jungen Aktivistinnen und Aktivisten auf die Straßen und fordert ein Umdenken in der Klima- und Umweltpolitik. Doch trotz breiter Unterstützung für das Anliegen erzeugt die Fridays-for-Future-Bewegung ein Konfliktfeld. Da die Schulstreiks für das Klima am Freitagvormittag stattfinden, stehen sie im eindeutigen Konflikt mit der staatlichen Schulpflicht und involvieren zwangsläufig die Lehrkräfte in den Kontext der Fridays-for-Future-Bewegung. Lehrerinnen und Lehrer hatten praktisch keine Möglichkeit, sich der Bewegung zu entziehen und waren gefordert, mit der Situation umzugehen. Die Lehrkräfte mussten dafür nicht nur Wege finden, dieses außergewöhnliche politische Phänomen im Unterricht zu thematisieren, sondern auch Lösungen, wie mit streikenden Schülerinnen und Schülern verfahren werden kann. Diese Arbeit nimmt die Lehrkräfte und Schulen in den Blick und damit eine neue Perspektive auf Fridays for Future ein. Dabei ist zum einen von Interesse, aus welchen Beweggründen die Lehrerinnen und Lehrer bestimmte methodisch-didaktische Entscheidungen getroffen haben, um dieses aktuell-politische Phänomen im Unterricht (nicht) zu thematisieren. Zum anderen wird betrachtet, wie sich der Umgang mit Schülerinnen und Schülern gestaltet, die am Freitag der Schule fernbleiben, um eine Fridays-for- Future-Demonstration zu besuchen. In beiden Dimensionen liegt der Fokus dieser Arbeit auf den individuellen Erfahrungen und Entscheidungsfindungsprozessen der Lehrkräfte.:1. Einleitung 2. Theoretische Grundlagen 2.1 Theoretische Einordnung 2.1.1 Definition des Begriffes „Soziale Bewegung“ 2.1.2 Definition des Begriffes „Jugendprotest“ 2.2 Historische Zusammenfassung 2.3 Die Fridays-for-Future-Bewegung 2.3.1 Organisation und Aktionsformen der Bewegung 2.3.2 Entwicklung der Bewegung 2.3.3 Die Demonstrierenden 2.3.4 Fridays for Future und die Schulpflicht 2.3.5 Öffentliche Rezeption 3. Jugendprotest und politische Bildung 3.1 Politische Partizipation als Ziel Politischer Bildung 3.2 Nachhaltigkeit und Partizpation in der politischen Bildung 3.3 Politische Aktion und politische Bildung 3.4 Lernen durch Politische Aktion 4. Methodik 4.1 Theoretischer Hintergrund 4.1.1 Begründung der Forschungsmethoden 4.1.2 Forschungsperspektive 4.2 Datenerhebung mittels Interview 4.2.1 Methodenbegründung 4.2.2 Problemzentriertes Interview nach WITZEL 4.2.3 Datenerhebung 4.3 Datenauswerung durch Qualitative Inhaltsanalyse 4.3.1 Qualitative Inhaltsanalyse nach MAYRING 4.3.2 Vorbereitung der Datenauswertung 5. Darstellung der Ergebnisse 5.1 Schulorganisatorischer Umgang 5.2 Methodisch-didaktischer Umgang 5.3 Affektiver Umgang 6. Fazit und Ausblick 7. Literatur- und Quellenverzeichnis 8. Anhang 9 Selbstständigkeitserklärung

Plastics contribute 2 GTons to the global carbon footprint, today, several countries have set targets to achieve carbon neutrality. Plastics, being a major contributor to global carbon footprint, would need to be reduced significantly from our daily life to achieve that or a way needs to be devised to recycle them. A big bottleneck in this process is to reduce the consumption of thermosetting plastics or to reduce the emissions associated with plastic and move towards economical and environmentally safe plastics having a longer lifespan and efficient recyclability. Fused filament fabrication (FFF) is the most commonly used 3D printed technology available today. Its applications range from production of prototypes to hollow shafts, and fully functional commercial components. This technology is revolutionary in a sense that it offers advantages such as cheaper raw materials, high degree of customizability, production in smaller batches at lower costs, decrease in material wastage, rapid prototyping, and complex geometry. A number of thermoplastic polymers can be used with FFF technology to produce parts, in addition research is on going to print materials not commonly used for FFF process. Polyoxymethylene (POM) could be a viable option for utilization as FFF basestock for the production of tribologically functional components. POM is an engineering thermoplastic that offers high resistance to wear, low friction, excellent impact resistance, and good chemical resistance. These properties render it suitable for production of gear wheels and low load bearings. It is currently processed using traditional manufacturing methods such as injection and compression moulding, while its printability has received very little attention in the openly available literature. An attempt has been made in this thesis to fill up this research gap by providing insight into POM filament quality, and the thermal, mechanical, and tribological behaviour of POM printed parts. The influence of overfill and layer height on the bulk properties of the printed samples, its play with counterface surface roughness and applied load has also been investigated.

<div>The work discussed in this document seeks to integrate conductive additives with energetic material systems to offer an alternative source of ignition for the energetic material. By utilizing the conductive properties of the additives, ohmic heating may serve as a method for preheating and igniting an energetic material. This would allow for controlled ignition of the energetic material without the use of a traditional ignition source, and could also result in easier system fabrication.</div><div>For ohmic heating to be a viable method of preheating or igniting these conductive energetic materials, there cannot be significant impact on the energetic properties of the energetic materials. Various mass solids loadings of graphene nanoplatelets (GNPs) were mixed with a reactive mixture of aluminum (Al)/polyvinylidene fluoride (PVDF) to test if ohmic heating ignition was feasible and to inspect the impact that these loadings had on the energetic properties of the Al/PVDF. Results showed that while ohmic heating was a plausible method for igniting the conductive energetic samples, the addition of GNPs degraded the energetic properties of the Al/PVDF. The severity of this degradation was minimized at lower solids loadings of GNPs, but this consequently resulted in larger voltage input requirements to ignite the conductive energetic material. This was attributable to the decreased conductivities of the samples at lower solids loading of GNPs.</div><div>In hopes of conserving the energetic properties of the Al/PVDF while integrating the conductive additives, additive manufacturing techniques, more specifically fused filament fabrication, was used to print two distinct materials, Al/PVDF and a conductive composite, into singular parts. A CraftBot 3 was used to selectively deposit Conductive Graphene PLA (Black Magic) filament with a reactive filament comprised of a PVDF binder with 20% mass solids loadings of aluminum. Various amounts of voltage were applied to these conductive energetic samples to quantify the time to ignition of the Al/PVDF as the applied voltage increased. A negative correlation was discovered between the applied voltage and time to ignition. This result was imperative for demonstrating that the reaction rate could be influenced with the application of higher applied voltages.</div><div>Fused filament fabrication was also used to demonstrate the scalability of the dual printed conductive energetic materials. A flexural test specimen made of the Al/PVDF was printed with an embedded strain gauge made of the Black Magic filament. This printed strain gauge was tested for dual purposes: as an igniter and as a strain sensor, demonstrating the multi-functional use of integrating conductive additives with energetic materials.</div><div>In all, the experiments in this document lay a foundation for utilizing conductive additives with energetic materials to offer an alternative form of ignition. Going forward, ohmic heating ignition may serve as a replacement to current, outdated methods of ignition for heat sensitive energetic materials.</div>