In Situ Atmospheric Plasma Treatment Enables First‐Layer Adhesion of <scp>PEEK</scp> on Borosilicate Glass for <scp>FDM</scp> ‐Printed Non‐Assembly Mechanisms

ABSTRACT Fused deposition modeling of poly‐ether‐ether‐ketone (PEEK) requires a high‐temperature build plate, yet PEEK does not adhere well to a borosilicate glass plate under standard process conditions, preventing printing without adhesive agents or specialized plates. We show that treating only the build plate before printing is insufficient, because the arriving PEEK melt remains chemically inactivated, and that pre‐treating the filament fails because the introduced functional groups are lost at the nozzle temperature of about 385°C–420°C. To overcome this, an atmospheric plasma source (compressed air) was mounted on the print head and directed into the gap between printer nozzle and build plate so that the PEEK melt and the substrate are activated simultaneously at the moment of contact. Owens‐Wendt analysis shows that both surfaces carry a low polar surface energy component under process conditions (PEEK 16.3, glass 14.2 mN/m) and that plasma raises both to a comparable, elevated level (30.7 and 26.0 mN/m). The simultaneous in situ treatment gives a pull‐off adhesion of 0.22 ± 0.03 MPa ( n = 4), with adhesive failure over at least 90% of the nominal area, whereas bed‐only and untreated surfaces show no adhesion. A coupled surface‐energy and thermal analysis yields a two‐condition bonding model, requiring both chemical activation and a thermal window set by the substrate effusivity and that explains the observed substrate selectivity. The method makes PEEK non‐assembly mechanisms printable without adhesive agents.