https://www.um.edu.mt/library/oar/handle/123456789/145210 2026-10-30T23:21:42Z https://www.um.edu.mt/library/oar/handle/123456789/150521 Title: 5-axis indexing additive manufacturing towards quasi-isotropic components Abstract: This project addresses the inherent mechanical limitations of traditional 3-axis Fused Filament Fabrication (FFF) and Fused Granular Fabrication (FGF), specifically the issue of anisotropy caused by planar layer deposition. While 3D printing has seen significant advancements in material variety and surface quality, the variation in mechanical strength relative to layer orientation remains a critical hurdle for structural engineering applications. The primary aim of this research was to mitigate mechanical anisotropy by leveraging the multi-directional deposition capabilities of 5-axis Additive Manufacturing (AM). By transitioning from traditional planar layering to 5-axis toolpaths, the project sought to approach quasi-isotropic structural performance. To achieve this, the project set out to review current 5-axis hardware and software, select a polymer material known to exhibit significant anisotropy in 3D printing (PLA-CF10%), and design a custom case study geometry optimised for 3-axis, 5-axis indexing techniques, and compression testing. The experimental results demonstrated that while 5-axis indexing eliminates traditional support structures and alters compressive behaviour, it does not eliminate material anisotropy. For the 50 mm cubes, the 5-axis specimens achieved a higher average peak load of 56.9 kN in the Z-orientation compared to the 45.7 kN 3-axis baseline, yet global anisotropy remained at 15%, similar to the 17% observed in traditional 3-axis counterparts. Unlike the 50 mm cubes, which leveraged greater material mass to withstand higher forces, the 35 mm cubes suffered a severe reduction in compressive strength under 5-axis indexing. This drop was most pronounced in the X-orientation, where peak stress fell from 15.51 MPa in the 3-axis baseline down to 7.81 MPa. This dual-scale analysis highlighted that smaller cross-sectional areas are exceptionally vulnerable to wall buckling and localised shear along block boundaries, revealing that multi-axis indexing seam lines act as internal stress concentrations that initiate premature failure. The study concludes that although multi-axis indexing can reinforce specific load-bearing faces, its mechanical reliability is strictly limited by its discrete nature and geometric scale. Future advancements should focus on continuous 5-axis slicing software to enable conformal toolpaths that follow internal stress lines, potentially eliminating the weak bonding interfaces observed in the indexing method. Description: B.Eng. (Hons)(Melit.) 2026-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/150519 Title: Digital light processing based fabrication of biomimetic micro-moulded polymer inserts for antifouling applications Abstract: Surface fouling is a major challenge in biomedical and engineering applications, where biological contaminants can reduce efficiency, hygiene, and overall performance. Bioinspired shark-skin micro-riblet structures have emerged as a promising passive antifouling solution. However, accurately replicating these microscale riblets remains challenging. This study assessed the feasibility of fabricating two biomimetic test artefacts, TA1 and TA2, with different riblet geometries. TA1 featured larger riblets than TA2. The artefacts were produced using a process chain combining Digital Light Processing (DLP)-based rapid tooling (RT) with micro-injection moulding (μIM), followed by a series of characterisation methods and experiments. Material characterisation showed that post-curing significantly affects the performance of IM-HDT resin. Notably, a twenty-minute cure at 230°C was shown to provide the ideal balance among thermal and mechanical properties, and structural integrity, whereas longer curing led to degradation. Digital Light Processing (DLP) experimental validation showed that optical over-curing and feature aspect ratio strongly influence dimensional accuracy, thus requiring compensation strategies to achieve the design target dimensions. The μIM process successfully replicated the inserts in polypropylene (PP), producing consistent micro-riblet structures with high precision. Wettability and surface free energy analyses showed that the replicated riblets modified liquid-surface interactions, indicating improved antifouling behaviour. The TA2-inspired design exhibited the most stable hydrophobicity and lowest surface energy, suggesting that smaller riblet geometries provide better antifouling performance. Overall, the research demonstrated that combining DLP-based RT with μIM is a feasible approach for producing functional biomimetic shark-skin micro-riblet structures. Nonetheless, well-defined materials, process parameters, and microscale design are essential to achieve accurate riblet geometries. Description: B.Eng. (Hons)(Melit.) 2026-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/150518 Title: Sustainability assessment of mechanical polymer recycling Abstract: Thermosets present a significant end-of-life challenge owing to its permanently crosslinked molecular structure, which prevents conventional thermoplastic recycling routes. This results in most thermoset waste being disposed through landfill and incineration. This study conducts an Integrated Life Cycle Assessment and Life Cycle Costing of mechanical processing of post-industrial thermoset epoxy waste as a particulate filler in different thermoplastic composite systems, evaluating whether this dual valorisation strategy represents a viable and circular alternative to conventional disposal. Five thermoplastic matrices were assessed across thermoset content levels of 10, 30, 50, and 100 percent with three composite end-of-life strategies and conventional disposal routes. The Life Cycle Assessment was conducted using SimaPro 9.2.0.1 with Ecoinvent 3.7.1 and ReCiPe 2016 Hierarchist endpoint methodology. Life Cycle Costing adopted a facility operator perspective capturing material procurement, processing, disposal, and transport costs per declared unit of 1000 kg of thermoset waste, complemented by a Cost of Ownership analysis over a 10-year facility lifetime. Life Cycle Assessment results demonstrate that environmental viability is fundamentally context-dependent. This is because thermoset incorporation increases environmental burden when the remainder is being sent to landfill. However, it delivers meaningful reduction of up to 47.5 percent in global warming potential when the remaining thermoset is incinerated, with recycled polypropylene consistently achieving the lowest burden across all scenarios. Life Cycle Costing results demonstrate that composite production costs approximately 22 times more per declared unit than conventional disposal, with milling labour and overhead dominating processing costs at high thermoset loading. The integrated assessment concludes that thermoset waste valorisation is environmentally justified but financially premature under current market conditions. The most viable entry point is a recycled thermoplastic matrix at 50 percent thermoset content replacing conventional incineration and the composite sent for recycling at end-of-life (EOL). This study provides the quantitative environmental and financial foundation for identifying the conditions under which viability is achieved. Description: B.Eng. (Hons)(Melit.) 2026-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/150517 Title: Design and prototyping of a modular upper-body exoskeleton for human-centred industrial operations Abstract: Work-related musculoskeletal disorders account for 72% of all work-related ill health in European manufacturing and cost UK industry an estimated £22.9 billion annually. Existing commercial exoskeletons either offer limited passive assistance at low cost or full active capability at prices exceeding €8,000, leaving most small and medium enterprises without a viable option. This dissertation addresses that gap through the design and prototyping of a modular hybrid upper-body exoskeleton targeting workers performing repetitive elevated-arm tasks such as pipe insertion and overhead assembly. The design followed the Roozenburg and Eekels Basic Design Cycle, progressing from a structured end-user survey and Product Design Specification through four synthesis stages to a fully evaluated detailed design. A hybrid architecture combining passive spring gravity-compensation with a CubeMars AK70-10 quasi-direct drive motor for powered elbow assistance was selected from four conceptual alternatives. Biomechanical analysis established a governing cable tension of 1,233.8 N, and material selection using Ashby's methodology identified Al 6061-T6 for all primary load-bearing components, confirmed by FEA which demonstrated a 41% reduction in forearm deformation. The final design accommodates users from the 5th to 95th anthropometric percentile, integrates a full sensor suite, and includes an audio-visual cognitive assistance module. At a recommended unit price of €3,047, it sits at the accessible end of the commercial market while delivering active hybrid functionality. A full-scale PLA prototype was tested across four phases. Passive subsystem testing confirmed effective gravity compensation with no range-of-motion restriction exceeding 10%, and electronic testing validated the full motor drive chain via CAN bus in MIT mode. Cognitive aid testing showed audio-guided participants completed a fault-finding task 68% faster with fewer errors. Two structural defects identified during testing, both caused by incorrect FDM print orientation, were resolved through targeted redesign. The results confirm that the project objectives have been substantially met at prototype scale. Description: B.Eng. (Hons)(Melit.) 2026-01-01T00:00:00Z