PSI - Issue 42

Manuel Sardinha et al. / Procedia Structural Integrity 42 (2022) 1274–1281 M. Sardinha et al. / Structural Integrity Procedia 00 (2022) 000–000

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Both the results of B and G series demonstrate that ironing application can successfully reduce warping. These experiments all commonly focused on introducing ironing within the first three layers of the build process. To summarise, Figure 7 shows a qualitative assessment of the results that allow a final comparison between the average of the tested hypothesis. For this analysis, four main criteria were defined: warping reduction, lateral appear ance, bottom appearance, and printing time. In each criterion, a score from 1 (very unsatisfactory) to 6 (optimised) was used.

Fig. 7: Quantitative comparison of research hypothesis.

4. Final Remarks

In this study, the authors follow the results of a previous work [17] that suggested the ironing process as a potential processing technique to reduce the warping of FFF parts. To explore the influence of ironing, the authors first sought suitable conditions to potentiate consistent warping in ABS cuboid specimens. For this purpose, various parameters such as build platform adhesion type, build platform temperature and printing temperature su ff ered iterations, which allowed a deeper understanding of the warping phenomena in fused filament fabricated parts. Since no mechanical tests were performed, results are purely evaluated concerning the prints’ geometric accuracy and visual aspect. Authors confirm that the bed coating is one of the most determining factors when aiming for warping reduction. Furthermore, solemnly applying glue or equivalent to the build platform is not always the most e ff ective way to avoid warping parts, especially when employing high bed temperatures. The first significant result to be noted is the set of settings and circumstances and their relation to specimen shape, which were achieved to e ff ectively and consistently replicate warping, demonstrating that this natural distortion in ABS parts can be controlled. Secondly, this research supports the claim of previous works [17] regarding the ironing process potential to reduce warping probability. It should be noted that even in scenarios where applying the ironing process throughout the specimen can reduce warping, it also increases production time and creates a localized lack of internal cohesion in the FFF part. In the future, such issues can be improved by widening ironing process capabilities and processing parameters. Another downside of using ironing to combat warping is the additional processing phase, referred to as ’mid-processing’ in this study, where the g-code must be updated to include ironing layers across the part. Concerning the results of the di ff erent tested hypotheses debated in the previous section, it is clear that overuse of ironed layers might easily be the source of unforeseen geometrical distortions. Nevertheless, results indicate that only applying the ironing technique within the first three layers of the specimen gives the most consistent warping reduction while minimizing secondary distortion e ff ects. Furthermore, 1 to 3 ironed layers do not significantly extend the production time of specimens. For the cuboids of this study, each ironed layer increments approximately 5% of build time. Even so, in FFF parts with a large contact area with the build platform, the time increment that comes from the introduction of ironing paths could have a more expressive influence on the final production time. For this reason, in the future, partially ironing the first layers of a specimen to selectively control the cooling shrinking forces could potentially reduce the warping of parts while minimizing additional production time, which should be particularly useful for parts with a large contact area with the build platform. Among the potential future research related to the influence of ironing in FFF parts, authors suggest the following paths: 1. Quantify the e ff ect of partially ironing one layer of a part instead of ironing a complete layer; 2. Evaluate the influence of di ff erent ironing distances, and ironing temperatures (which should directly a ff ect ma terial drainage and final visual aspect); 3. Further study the size and shape sensibility of these results.