PSI - Issue 77

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

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

2.2. Process Parameters Main process parameters greatly dictate the heat input that is applied to the raw material by the laser. The parameters for this work were Laser power as 285 W, Laser Speed as 960 mm/s, hatch spacing as 0.11 mm and layer thickness 40 µm. The pattern of laser movement is rotated by 47° and shifted in between every layer. These parameters were identical for all samples that were built for this work. The building platform temperature was kept at 40 °C throughout the printing process. 2.3. Experiment Design During SLM process, the raw powder is laid over the building platform by the help of a so called “Recoater” mechanism. The layer thickness selected for prints in this work is 40 µm therefore it can be said that the height of gap to be filled by powder for each layer is around the layer thickness value. This value also dictates the maximum amount of deformation on the part, that would not hinder recoating and stop the built. In addition, since the powder is dragged by recoating blade across building platform which results in friction forces between the powder particles, as well as friction between the powder and part surface. The design of the print should provide sufficient stiffness to encounter such forces. Building parts that have small cross-sections are prone to deformation as the building height increases. This is due to possible local over-heating and poorer heat conductivity that comes from smaller cross-section to length ratio.

Figure 4 Tensile bars and experimental setup design for printing them.

Thus, long parts, that have small cross section perpendicular to the building direction, might be challenging to print. In the first picture, the front-view of the tensile sample is given and its thickness is 1.3 mm. In the second image the orientation of the parts and solid prop supports can be seen. The goal with such support design is to provide stiffness and higher conduction rate at high building height for this part. Arrows point out the “pockets” of solid material that is printed to act as heat sink as well as stiff prop supports to house supports structures on top of them. The amount of support was shown to directly influence the conduction rate thus monitoring data[7]. Hatching lines indicate the track of the laser beam’s movement during exposure of metal powder. Hatching lines are parallel to and at the distance set by the process parameter “hatch distance”. However, proximity of hatching lines may result in over-heating while scanning of smaller cross-sections due to the fact that bigger amount of lines, that are exposed per unit time as well as increased overlapping between melted material tracks. With this work two different strategies are tested. While one of them is a default strategy that might lead to over-heating in small cross-sections, with the other strategy idle times are added between exposure of short hatching vectors to avoid local over-heating.