PSI - Issue 77

Y. Bakir et al. / Procedia Structural Integrity 77 (2026) 639–648 Y.Bakir et al./ Structural Integrity Procedia 00 (2026) 000–000

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Figure 12 Residual stress curves as orange curves referring results obtained by default scanning strategy and blue curves refer to idle time strategy[4]. 4. Conclusions In order to overcome challenges that might arise from printing thin and long tensile specimens, a special experiment setup was designed to optimize printability. The building process was monitored by Optical Tomography in situ monitoring system. Two different scanning strategies, their influence on tensile properties were tested. In addition, for the purpose of observing melting track formation, rectangular prism shaped parts were built. The data gathered by monitoring system should be evaluated with respect to the experiment setup. • Idle time introduction between the hatching lines significantly altered the melting track formation near the edges of the parts. Idle time seem to have caused the separation of the melting tracks. Shrinkage of the melted material is influenced as well. The average width of the melting tracks formed with default process settings was 165 µm while with idle time the width was 95 µm. • There was not any process interruption, therefore it can be said the experiment design consisted of prop supports provided sufficient stiffness and heat transfer in order to avoid excess overheating and deformation. • Monitoring system consisting of a thermal camera was sensitive to the changes in the scanning strategy. The radiation emitted from the melt pool had lower average and lower standard deviation with the idle time strategy. Based on this data, it can be said that, idle time strategy was less susceptible to the changes in the scanning strategy that occur in between layers. • According to the single layer images the idle time also results in more stable melting across a layer. While, default process settings resulted in localized higher GV o, idle time strategy could be used for prevention of possible local over-heating. • According to the residual stress measurement idle time strategy resulted in lowering the residual stress significantly. • Finally, there was not any significant difference with mechanical properties of the parts that were tested for this work. Variation in the monitoring data and melting track formation did not translate to any changes in the mechanical properties. As it can be seen from the results, in situ monitoring system is sensitive to the changes in the process settings. And its utilization can help for improving the understanding of SLM process phenomena. During production of parts there are multiple factors and mechanisms affecting the high-speed local melting and these phenomena should be considered for assessing the process stability.