Sand casting is used to manufacture large metal workpieces. The processing is executed by pouring molten metal into a sand mold. During the process, the mold is subjected to mechanical and thermal stress. It is of economic interest to inspect the molds for defects that can affect casting results, in the worst case leading to discarded products. This thesis investigates and proposes an automated solution for inspecting surface cracks in sand molds. A hybrid solution using image processing and convolutional neural networks has been developed. The first is to find and implement a crack detection method that can perform equally well or better than a human. The second objective is to investigate the amount of training data needed. Twenty-one machine learning models have been trained to evaluate the impact training data size along with transfer learning, fine-tuning, data augmentation, and image processing have on performance. As a result, it was found that the image processing part of the method is not effective in finding cracks in its current form. However, the convolutional neural network still achieves good performance. The method has been trained and tested on sand mold core images captured with a test workbench along with images of concrete walls and pavement acquired from the SDNET2018 data set. Sand mold images achieve 82% accuracy and 79% recall when training on 90 images while testing on 28 images separate from training. A maximal performance of 97.9% accuracy and 99.7% recall is achieved when training on 5400 SDNET2018 images and then testing on 608 images. When training on 100 SDNET2018 images and tested on the same 608 images, a performance of 86.0% and 96.7% recall is achieved. It is concluded that the proposed solution is feasible. Transfer learning and data augmentation are essential techniques to achieve good performance if a small amount of data is available, while fine-tuning may give a slight performance boost. Further work should be performed considering the impact of curved geometry on performance. Investigating alternative structures of the convolutional neural network and testing alternative hyperparameters may improve generalization performance. The image processing performance may be improved if the manufacturing process is more precisely defined, as parameters can be more optimally tuned.

Introduction: Production systems go through changes over time and there are different factors driving the change. Metal Additive manufacturing (AM) could be a factor with industries that already havetaken interest in the manufacturing technique. Qualification and standards of manufacturing guide consistent product quality and could face challenges when implementing AM. However,most publications about metal AM are currently posted from a material point of view. This requires more publications with comprehensive overviews of metal AM and dive deeper into metal AMs industry applications, limitations and challenges. Purpose: The purpose of this thesis is to identify challenges that may arise in the implementation of AM. The intention is also to compare the conventional method of sand casting with AM for metal production targeted at excavators. This is accomplished by specifically highlighting the metallurgical benefits of AM. Research Questions: RQ1: What challenges arise when qualifying AM products for excavators? RQ2: What are the metallurgical benefits of an AM produced product in comparison to a Sand Casted product for excavator bucket teeth? Method: An inductive approach has been taken, with a literature, empirical and case study conducted.The construction of the theoretical framework used information from scientific articles and books. The findings of the empirical study arrived from information gathered through observations and experimentation, with help and interpretation from the case companies. The empirical findings will assist in answering the research questions. The case study consisted of metallurgical testing in form of porosity analysis, microstructure examination, hardness- and chemical composition test. Conclusion: Several challenges were discovered that will impact the qualification of AM products. These can affect the results derived from the case study, providing incorrect data. It can however be seen as beneficial as it provides knowledge of how to reduce or eliminate their impact withfuture analyses.The AM products tested, displayed positive metallurgical properties in comparison with sand casted products. A standout trait was the consistency in the dimension and density of the AM products, displaying how AM can create nearly identical products.

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På Volvo Group Trucks Operations (GTO) i Skövde tillverkas cylinderblock, cylinderhuvud och svänghjul genom gjutning med sandformar. Då formverktygen som formar sandformarna fylls uppkommer slitage där sandpartiklarna träffar, vilket leder till att formverktygen behöver underhållas regelbundet.Målet med denna studie är att hitta alternativa material som formverktygen kan tillverkas i alternativt förstärkas eller beläggas med för att minska slitaget i formverktygen och på så sätt minska kostnader genom att förlänga underhållsintervallen. Problemet analyseras och en litteraturstudie kring erosiv och abrasiv nötning genomförs.Ett antal material tas fram genom en materialvalsprocess som lämpliga kandidater baserat på litteraturstudien, materialkartor och diskussion. Materialprover testas med en standardmetod för erosion med gasburna partiklar. Resultat från tidigare empiriska studier tyder på att erosion påverkas starkt av materialegenskaper så som hårdhet och seghet men även de eroderande partiklarnas infallsvinkel och hastighet.Erosionstestet utförs för 30 och 90 graders infallsvinkel. Testet visar att de mjukare stålen, Holdax och Sverker 21, har högre beständighet mot erosion vid låga infallsvinklar och det hårdare stålet Nimax har högre beständighet vid höga infallsvinklar. Nimax anses vara ett lämpligt material till formverktyget då Nimax har den totalt lägsta erosionstakten vid hopslagning av den totala erosionstakten över båda infallsvinklarna. Nimax har den lägsta erosionstakten vid 30 graders infallsvinkel och anses även ha god beständighet mot erosion vid 90 graders infallsvinkel.Rekommendation ges kring upprepade erosionstester för att säkerställa resultatet. Rekommendationer finns också kring materialprovning i formverktyget för att se om ett materialbyte skulle leda till besparingar. Undersökning av möjligheter att konstruera bort nötning i formverktyget genom ändring av infallsvinklar mellan den inblåsta sanden och formverktyget, samt ändring av lufttryck rekommenderas. / At Volvo Group Trucks Operations (GTO) in Skövde, cylinder blocks, cylinder heads and flywheels are manufactured through sandcasting. As the forming tools that forms the sand forms are filled with sand, wear occurs where the sand particles hit the tool surface. The forming tool thus needs to be regularly maintained. The aim of this study is to evaluate alternative materials that the forming tools can be manufactured in to reduce wear, and thereby reducing costs by extending maintenance intervals. The problem is analyzed and a literature study on erosive and abrasive wear is carried out. A number of materials are presented as suitable candidates based on the literature study, material charts and discussion. Material samples are tested using a standard method for solid particle erosion using gas jets. Results from previous empirical studies indicate that erosion is strongly influenced by material properties such as hardness and toughness but also the angle of impingement and velocity of the erosive particles.The erosion test is performed at 30 and 90 degree angle of impingement. The test shows that the softer steel, Holdax and Sverker 21 have higher resistance to erosion at low angles of impingement and the harder steel Nimax has higher resistance at high angles of impingement. Nimax is considered a suitable material for the forming tool, as Nimax has the overall lowest erosion rate when adding the total erosion over both angles of impingement. Nimax has the lowest erosion rate at 30 degrees angle and is also considered to have good resistance to erosion at 90 degrees angle. Recommendation is given on repeated erosion tests to validate the results. There are also recommendations regarding material testing in the forming tool to see if a material change would lead to savings. Examination of possibilities to make changes in the sand filling process, altering angle of impingement between the sand blown and the forming tool as well as air pressure is recommended.

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / The contribution of the metalworking sector to the gross domestic product is decreased by 8.6% in the 2017–2018 period because of problems such as high rejection rates, lead times, and raw material losses. Consequently, the sector’s production was reduced by PEN 1,200,000 while demand remained flat. Thus, this article proposes a production control model using 5S, Single-Minute Exchange of Dies, and tools such as Kanban and Constant Work-in-Progress (CONWIP) to increase the productivity of a sand casting line in a Peruvian metalworking enterprise that manufactures parts for mining on request. The improvement proposal involves the implementation of lean manufacturing tools and analyzes low productivity effects. The problems identified are typical of the Peruvian metalworking sector; thus, this study may contribute to finding possible solutions for issues faced by other enterprises. / Revisión por pares

While Aluminium has lots of unique properties and is seen as a material of the future, its production and manufacturing has significant environmental impacts. For complex and dimensional shapes casting remains the main manufacturing method and in this study the environmental pressure of different casting techniques is compared. A screening LCA is conducted to determine the environmental impacts of plaster mould castings in a case study at the Ventana Hackås AB foundry in Mid Sweden. The findings are compared to models of sand, pressure die and lost wax castings, based on literature datasets. The most relevant factors for the environmental performance are identified as the production of the aluminium alloy and the amount and source of energy. For plaster mould castings additionally the plaster consumption is significant, while lost wax castings are dominated by the mould production and general processes. Under similar circumstances a relatively similar performance was found for all casting techniques except the lost wax process, which is at least 3 times more emission intensive. Of the remaining techniques pressure die castings performed the best and plaster mould castings the worst, but different sources of uncertainties have been identified in this comparison. In addition a carbon footprint interface is created based on these findings, to enable specific comparisons of different casting method setups. Customizable variables allow the adaptation of three scenarios to real world conditions. As the main influencing factors the aluminium alloy, source of electricity and casting technique have been identified. / <p>2018-10-10</p>

Gegenstand der Arbeit ist die Untersuchung der Gefügebildung dünnwandig erstarrter Eisenlegierungen und deren Auswirkung auf die mechanischen Eigenschaften. Die Arbeit ist in zwei Teile untergliedert. Im experimentellen Teil wurden Stahlgusslegierungen unter Variation ihrer Zusammensetzung erschmolzen und in Quarzsandformen vergossen. Das erhaltene Probenmaterial wurde im Gusszustand sowie nach optional angewendeten Wärmebehandlungen untersucht. Die Abhängigkeiten zwischen chemischer Zusammensetzung, Gefügeausbildung und mechanischen Eigenschaften wurden quantitativ dargelegt. Der Modellierungsteil enthält die Ergebnisse der Simulation des Gieß- und Erstarrungsprozesses eines ausgewählten Stahlgusswerkstoffs. Zur Durchführung der Simulation kamen kommerziell verfügbare Softwarepakete zum Einsatz. Die Ergebnisse wurden mit experimentell ermittelten Daten verglichen und die Adäquatheit der Simulation beurteilt. Die Anwendbarkeit der genutzten Simulationsmethoden auf den Bereich dünnwandiger Stahlgussteile wurde aufgezeigt.

This thesis deals with solving the most serious internal defects in castings made of aluminum alloys which are cast in sand molds in Slévárna a modelárna Nové Ransko Ltd. The problem solving contains a description of the problematic castings with the investigation of the structure and phases and subsequent detailed analysis of their production. The Author of this thesis also examines the influence of Fe and Mn on a possible formation of the internal porosity with the help of test meltings with the evaluation of the internal structural change. The Author’s design solution is a close checking of chemical composition with regard to the ratio Mn / Fe present in the alloy, the purchase of Foundry Degassing Unit to reduce gassiness of melted metals and better control of gassiness with the help of the appropriate equipment for the density Dichte index.

Gegenstand der Arbeit ist die Untersuchung der Gefügebildung dünnwandig erstarrter Eisenlegierungen und deren Auswirkung auf die mechanischen Eigenschaften. Die Arbeit ist in zwei Teile untergliedert. Im experimentellen Teil wurden Stahlgusslegierungen unter Variation ihrer Zusammensetzung erschmolzen und in Quarzsandformen vergossen. Das erhaltene Probenmaterial wurde im Gusszustand sowie nach optional angewendeten Wärmebehandlungen untersucht. Die Abhängigkeiten zwischen chemischer Zusammensetzung, Gefügeausbildung und mechanischen Eigenschaften wurden quantitativ dargelegt. Der Modellierungsteil enthält die Ergebnisse der Simulation des Gieß- und Erstarrungsprozesses eines ausgewählten Stahlgusswerkstoffs. Zur Durchführung der Simulation kamen kommerziell verfügbare Softwarepakete zum Einsatz. Die Ergebnisse wurden mit experimentell ermittelten Daten verglichen und die Adäquatheit der Simulation beurteilt. Die Anwendbarkeit der genutzten Simulationsmethoden auf den Bereich dünnwandiger Stahlgussteile wurde aufgezeigt.:1 Einleitung 2 Grundlagen 2.1 Keimbildung 2.2 Unterkühlung 2.3 Erstarrungsmorphologie 2.4 Gießfehler 2.5 Erkenntnisstand und Defekte 3 Aufgabenstellung und ihre Präzisierung 4 Kleintechnische Versuche zur Herstellung dünnwandiger Stahlgussteile 4.1 Genutzte Anlagen und Untersuchungsmethoden 4.2 Auswahl der Versuchslegierungen 4.3 Ergebnisse der experimentellen Untersuchungen 4.3.1 Duplexstahl 4.3.2 Ferritisch-bainitischer TRIP-Stahl 4.3.3 Bainitischer luftvergüteter Stahl 5 Modellierung des Erstarrungsprozesses 5.1 Simulationsmethoden 5.2 Formfüllsimulation 5.3 Erstarrungssimulation 5.4 Bewertung der Simulationsergebnisse 6 Zusammenfassung 7 Literaturverzeichnis 8 Tabellen 9 Bilder Anhang