PSI - Issue 83

Miloslav Kepka et al. / Procedia Structural Integrity 83 (2026) 138–145

142

3.1 Recoating system This paper addresses the powder deposition process, which is done by the recoating assembly, called the recoater. In the EOS M290 system used for this work, the assembly consists of a recoater arm mounted on a linear guide, driven by a stepper motor via a synchronous toothed belt. The recoater blade is mounted from the bottom side to the recoater arm by a longitudinal plate and several bolts. Precise vertical positioning is ensured by lateral stops, against which the blade rests due to its geometry and self-weight.

Fig. 4. Recoating system.

Fig. 5. Recoater blade mounting.

3.2 Powder bed defects Improper deposition of a new powder layer can lead to several types of defects. The most prevalent and critical defects are described below: Waves is the most dangerous defect type. It occurs when the recoater blade strikes and vibrates against a part that has raised above the powder bed level, often due to thermal expansion caused by insufficient heat dissipation into the building platform. This typically occurs during the transition from support structures to solid cross-sections. Another cause of protrusion is the release of residual stresses, leading to part deformation. These vibrations result in uneven powder distribution, characterized by regions of insufficient and excessive layer thickness in the wave pattern. In severe cases, sections of the part remain entirely uncovered by powder, causing extreme overheating upon laser exposure.