One of the most significant parameters of the Fused Deposition Modelling (FDM) for 3D printing process is the raster angle. In this study, the five different raster angles are used to fabricate the 3D parts using thermoplastic material - polylactic acid (PLA), and tensile properties of these parts are investigated to identify the best raster position to fabricate the strongest 3D printing part. In this study, the microstructural analyses on fracture interface, and on outer and inner surfaces of these 3D parts are performed using a scanning electron microscopy (SEM) to examine material failure modes and reasons, and defects in the 3D parts. This study identified the best raster orientation to lie down the layers of 3D printing material during the process. This study also identified that there are several defects in 3D printed parts at micro level that have large impact on mechanical properties of 3D printed part.

Fused deposition modelling (FDM) is a popular but complex additive manufacturing process that works with many process parameters which are crucial to investigate. In this study, 3D parts were fabricated by placing each filament layer in opposite direction to the others; for this, two combinations of raster angles, (45° −45°) and (0° 90°), along with three different infill speeds were used. In this study, two 3D printing material types—Polylactic Acid (PLA) and tough-PLA were used. The material properties of each 3D part were investigated to identify the best combination of these parameters. A microstructural analysis was also performed on outer and inner surfaces along with fracture interface of the parts after tensile testing using a scanning-electron-microscopy (SEM) to explain material failure modes and reasons. The results suggest that for both the material types, a raster angle of 45° −45° produces stronger parts than to a raster angle of 0° 90°. This study also suggests that a slow infill speed improves tensile properties by providing a better inner-connection between two contiguous roasters. Thus, the detailed analysis of microstructural defects correlated with tensile test results provides insight into the optimisation of raster angle and infill speed, and scope for improvement of mechanical properties.

Additive manufacturing (AM) has revolutionized the manufacturing industry by enabling the fabrication of complex geometries and designs with ease. 3D printing—fused deposition modeling (FDM) has emerged as a prevalent technique, owing to its versatility and cost‐effectiveness. However, the FDM process is complex and depends on multiple parameters, which makes it challenging to obtain high‐quality and consistent 3D printed components. The purpose of this study is to simplify the printing process for users and potentially improve the overall quality and consistency of printed objects. This research delved into optimising 3D printing parameters, specifically raster orientation and in‐fill speed, for PLA material through three experimental studies. The mean effect of these parameters and the effects of their interaction through analysis of variance (ANOVA) on tensile properties were also discussed. Initial experiments identified the most suitable parameters and its optimal values for PLA, which were then applied to five different materials: PETG, PLA tough, Recycle PLA, Plain PLA, and ABS. Tensile tests assessed the printed parts, and scanning electron microscopy (SEM) was employed to analyze fracture interfaces and material failure causes. This study identified a raster of 45°/−45° and 30 mm/s infill speed as optimal for diverse 3D printing materials. Notably, ABS, PETG, and tough PLA exhibited better tensile strengths, surpassing manufacturer benchmarks. However, Plain PLA and Recycled PLA, despite lower tensile strengths, proved valuable for specific applications. Interestingly, all tested materials showed greater flexibility than manufacturer recommendations, suggesting their suitability in scenarios needing both strength and flexibility. This study's results offer promising avenues for refining 3D printing practices, to the advantage of all users. The findings from this study offer significant insights for future research to investigate the effect of other process parameters on the quality of 3D printed parts, leading to further advancements of AM.Highlights: Optimised 3D printing parameters. Applicability of optimised settings extended across various materials. ABS, PETG, and tough PLA exceeded manufacturer benchmarks in tensile strength. Experimental and ANOVA findings are in good agreement, revealing significant process parameters.

This study presents a novel multi-material additive manufacturing (MMAM) strategy by combining virgin polylactic acid (vPLA) with recycled polylactic acid (rPLA) in a layered configuration to improve both performance and sustainability. Specimens were produced using fused deposition modelling (FDM) with various vPLA: rPLA ratios (33:67, 50:50, and 67:33) and two distinct layering approaches: one with vPLA forming the external layers and rPLA as the core, and a second using the reversed arrangement. Mechanical testing revealed that when vPLA is used as the exterior, printed components exhibit tensile strength and elongation improvements of 10–25% over conventional single-material prints, while the tensile modulus is largely influenced by the distribution of the two materials. Thermal analysis shows that both vPLA and rPLA begin to degrade at approximately 330 °C; however, rPLA demonstrates a higher end-of-degradation temperature (461.7 °C) and increased residue at elevated temperatures, suggesting improved thermal stability due to enhanced crystallinity. Full-field strain mapping, corroborated by digital microscopy (DM) and scanning electron microscopy (SEM), revealed that vPLA-rich regions display more uniform interlayer adhesion with minimal voids or microcracks, whereas rPLA-dominated areas exhibit greater porosity and a higher propensity for brittle failure. These findings highlight the role of optimal material placement in mitigating the inherent deficiencies of recycled polymers. The integrated approach of combining microstructural assessments with full-field strain mapping provides a comprehensive view of interlayer bonding and underlying failure mechanisms. Statistical analysis using analysis of variance (ANOVA) confirmed that both layer placement and material ratio have a significant influence on performance, with high effect sizes highlighting the sensitivity of mechanical properties to these parameters. In addition to demonstrating improvements in mechanical and thermal properties, this work addresses a significant gap in the literature by evaluating the combined effect of vPLA and rPLA in a multi-material configuration. The results emphasise that strategic material distribution can effectively counteract some of the limitations typically associated with recycled polymers, while also contributing to reduced dependence on virgin materials. These outcomes support broader sustainability objectives by enhancing energy efficiency and promoting a circular economy within additive manufacturing (AM). Overall, the study establishes a robust foundation for industrial-scale implementations, paving the way for future innovations in eco-efficient FDM processes.