Influence of process instabilities and elevated temperatures on mechanical properties of PBF-LB-manufactured polyamide 12

Purpose: This study aims to produce interrupted specimens, for which the print job was stopped for 3 min and subsequently continued by applying the next layer of powder. By testing tensile, flexural and impact properties, different loading cases are investigated for continuous and interrupted print jobs with further process defects. A temperature range of −20 °C up to 140 °C is tested for three orientations of continuously sintered specimens. Design/methodology/approach: To obtain reliable properties, the production process has to be stable and reproducible, i.e. continuous and without any interference, particularly for powder bed fusion-based (PBF) parts. In reality, many reasons lead to interruptions during production. Hence, the purpose of this study is to investigate the effects of interrupted print jobs and their impact on the mechanical performance of PBF-based polyamide 12 specimens. Findings: It is shown that a printing interruption during the build cycle without oxygen leakage or temperature drop does not negatively affect quasi-static mechanical properties but deteriorates the impact performance. For reference purposes, the tensile properties of continuously sintered specimens are analyzed from −20 °C up to 140 °C. A very strong temperature dependence of the mechanical performance is observed above the glass transition temperature. Originality/value: Unexpected interruptions can happen during print jobs, and their impact on the quasi-static properties and impact properties depending on the orientation is pointed out. Thus, even an interrupted print job can be used depending on the application case. Furthermore, this shows a possible application for future printers with purposely interrupted print jobs to embed, e.g. radio frequency identification tags.