Saudi Cultural Missions Theses & Dissertations

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    A techno-economic assessment of centralized vs. distributed aerospace manufacturing systems
    (Cranfield University, 2024-09) Alshurafa, Majid Makki; Haddad, Yousef
    This thesis provides a comprehensive techno-economic assessment comparing centralized and distributed aerospace manufacturing systems, with a focus on the use of additive manufacturing (AM) for producing turbine blades in aircraft engines. The study reveals that centralized manufacturing results in a higher cost per part at $463.97, largely due to logistics expenses, but offers greater financial stability with a positive NPV of $5 million. On the other hand, distributed manufacturing achieves a lower cost per part at $334.60 by eliminating logistics costs. Initially, this approach showed a negative NPV; however, after price adjustments, the distributed system could reach a significantly higher NPV of $38 million. Despite these cost benefits, distributed manufacturing carries higher financial risks due to its sensitivity to material cost fluctuations. These findings highlight the trade-offs between the operational stability of centralized systems and the potential cost efficiency of distributed systems when leveraging AM technology
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    Development of Robots and Algorithms for Cooperative Additive Manufacturing
    (University of Manchester, 2024-04-11) Alhijaily, Abdullah; Bartolo, Paulo; Cangelosi, Angelo
    Additive manufacturing (AM) is dominated by single robots which present limitations in fabrication time and efficiency of the system. To address this problem, this research explores the concept of cooperative printing in which multiple printheads fabricate the same part concurrently. However, configurations for cooperative printing in the literature present several limitations such as reduced cooperative printing area and cross prevention in which no two printheads are allowed to cross each other's paths during printing. Thus, a novel configuration is proposed in this research. This configuration was realised on a custom gantry machine. As shown, the proposed configuration allows printing parts that are impossible to print or inefficiently printed by other cooperative printing configurations. Furthermore, several novel algorithms are formulated and implemented in the developed machine. Additionally, efficient algorithms were developed for path planning that allowed to reduce the computation time of slicing for cooperative printing from minutes to milliseconds. Also, the proposed system significantly increased the printing speed surpassing the maximum printing time reduction reported in the literature. Conversely, mobile robots are promising for AM due to their large workspace. However, current plastic AM by mobile robots produce parts with poor quality and rough surface finish. Thus, an accurate mobile robot specialised for mobile AM is developed for this research. The proposed mobile robot's accuracy and precision were assessed and was found to have a 0.37 mm average error surpassing the literature on mobile AM. Finally, it was shown that the developed mobile robot surpasses them both in terms of quality and accuracy. For gantry systems, offline path planning is reliable and efficient due to their high accuracy and predictability. However, it is unreliable for low accuracy and error-prone systems such as mobile robots. To overcome this, an online cooperative printing path planning designed for the developed mobile robot is proposed. Several novel real time algorithms were developed, including a novel online collision avoidance algorithm that guaranteed collision-free motions. This research stands as the first work to develop fully online path planning for cooperative printing.
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    IMPACT DE LA FABRICATION ADDITIVE SUR LA PERFORMANCE DE LA SUPPLY CHAIN
    (Université de Bordeaux, 2023-11-29) Noorwali, Albraa; Ducq, Yves
    Additive Manufacturing (AM), often referred to as 3D printing, is a technology that allows for the direct creation of 3D products from digital models, offering industries new possibilities for design, customization, and rapid prototyping. Its impact spans industries such as aerospace, healthcare, and automotive, promising cost-effective production and innovative solutions. However, the quality of AM-produced products depends on the post-processing operation, and some non-quality issues are often encountered. Despite the extensive literature comparing AM to conventional manufacturing (CM), there is still a need for empirical evidence and comprehensive cost analyses to guide companies in adopting AM, especially by considering the non-quality issues. This thesis addresses this gap by (1) empirically investigating the impacts of AM across all supply chain processes by using collected data from a sample of 51 companies, (2) evaluating, by means of a simulation study and data from an oil and gas company, the practicality and cost-effectiveness of shifting from CM to in-house AM production while considering investment costs and different quality levels, and (3) exploring the advantages of integrating AM within a dual sourcing framework to assess cost implications and resilience benefits. The empirical investigation shows two major benefits of AM, namely: the ability to produce complex parts in low volumes and good design and the prototyping capability. Moreover, the simulation study provides evidence on the limits of AM when there is a low-quality level generated by postprocessing. The thesis enables as well to show the benefits of using AM within a dual sourcing context.
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    Remote Monitoring and Controlling of Additive Manufacturing Machines Using Industry 4.0 Principles
    (University of Manchester, 2019-11-22) Alhijaily, Abdullah; Bartolo, Paulo
    Manufacturing has seen many changes over the years; some of these changes correspond to new paradigms and are usually associated with industrial revolutions. Industry 4.0, the fourth industrial revolution, is continuing the improvements that the past industrial revolutions have done to manufacturing. It aims to impact the physical world by utilizing digital technologies. This research reviewed the concept of Industry 4.0 and key associated techniques such as the Internet of Things (IoT) and Cloud Computing. The ability to integrate different technologies in an Industry 4.0 environment to improve manufacturing is also discussed. Significant details are provided to additive manufacturing, a key element of Industry 4.0. However, as observed few attempts were made to integrate Additive Manufacturing with other technologies in an Industry 4.0 environment. This research addresses these limitations through the development of a computational application to remotely control and monitor any additive manufacturing machine, using cyber physical systems, cloud computing, and IoT. The research also applied the developed system on an additive manufacturing machine at The University of Manchester as a case study. The system opens up new dimensions for additive manufacturing by allowing the access of any machine from any place at any time. This improves the utilization of machines. Moreover, the system opens new opportunities for mass personalization.
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    An Investigation of The Effect of Rheo-Printing Technology on Big Area Additive Manufacturing
    (Saudi Digital Library, 2024-11-27) Alzahrani, Faisal J; Coulter, John P
    A novel processing innovation named Rheo-printing technology was introduced that could impact the field of the Big Area Additive Manufacturing (BAAM). The Rheo-printing technology applies a controlled circumferential and axial shear rate to the polymer melt before depositing the polymer through the printing nozzle. The rheological polymer properties modify due to the applied shear rate, and the ultimate goal is to enhance the product's properties. The application of the circumferential shear rate on the polymer melt is accomplished through a rotational printing nozzle. Adjusting the rotational speed of the printing nozzle controls the shear rate applied to the polymer melt, providing control over the rheology of the polymer melt. This research employs an extrusion-based AM machine that uses polymer pellets as a feedstock to investigate the impact of Rheo-printing technology on BAAM. The effect of Rheo-printing technology was investigated theoretically and numerically to examine the shear rate impact on the material's viscosity. Different shear-thinning polymers were included in the investigation; the viscosity influence of each polymer has been studied through a range of rotational speeds, and statistical analysis has been applied to the obtained results for a comprehensive understanding. The investigation compared the influence of Rheo-printing technology on two different nozzle sizes. For small additive manufacturing or desktop 3D printers, a 0.6 mm nozzle diameter was utilized, while a 2 mm nozzle diameter was employed for BAAM. Overall results showed that the effect of Rheo-printing technology appeared more significant with a bigger nozzle diameter. Also, there is a favorable correlation between nozzle rotation and viscosity for all polymers, regardless of nozzle diameter. Specifically, this correlation manifests as a decrease in viscosity as the nozzle is rotated, with the magnitude of this reduction becoming more pronounced at higher rotational speeds and near in the outermost region of the extruded polymer road. Two different numerical simulations were included to study the impact of the temperature on the printing process. The first numerical simulation was to study the effect of printing speed on the temperature evolution of each layer during the printing process. Results showed that the temperature fluctuation as each layer's heating and cooling during the printing process decreased with increasing the printing speed. The second numerical simulation was to study the platform temperature's impact on each layer's temperature evolution during printing. The effect of increasing the platform temperature was shown clearly on the cooling interval of each layer. Increasing platform temperature reduces the heat losses in the printed layer during the cooling interval. An experimental investigation also employed conventional printing and Rheo-printing technology to investigate the temperature evolution during printing and compare the obtained results. This investigation was performed by printing two samples using conventional and Rheo-printing technology and monitoring the temperature evolution during printing. The anisotropy and porosity of BAAM products were investigated, and the enhancement of Rheo-printing technology on product properties was validated numerically and experimentally. Three groups of different layer-building times were designed, and twenty-four samples were printed using conventional and Rheo-printing technology, investigating the impact of Rheo-printing technology on interlayer adhesion strength. Also, three configurations were designed, and eighteen samples were printed using conventional and Rheo-printing technology, investigating the effect of Rheo-printing technology on void formation. The enhancement of the Rheo-printing technology on mechanical properties of BAAM samples was validated where the anisotropy and porosity percentage were reduced.
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