Identification of the Influence of IPA Rinsing Times on Surface Roughness of SLA-Printed Parts Made of Different Materials

This study investigates the influence of isopropyl alcohol (IPA) washing time on the surface roughness of stereolithography (SLA)-printed parts fabricated using the Formlabs Form 3B+ printer. Three photopolymer resins provided by the manufacturer were evaluated: Gray, Tough 2000, and Rigid 10K. Samples were printed in standardized geometries and post-processed under controlled conditions, with IPA washing times ranging from 6 to 30 min, followed by UV post-curing. The surface roughness parameters (Ra, Rz, Rt, and RSm) were measured using a Taylor Hobson Form Talysurf i-Series profilometer under metrologically controlled conditions. The results revealed a clear correlation between increased IPA exposure time and improved surface finish, though the magnitude and monotonicity of this effect were material dependent. Rigid 10K exhibited the most consistent reduction in roughness with longer washing, while Tough 2000 showed substantial improvement with extended durations but also demonstrated temporary surface degradation at intermediate wash times. Gray resin achieved near-optimal roughness after moderate rinsing, with orientation-dependent differences observed. The findings indicate that the careful optimization of washing duration can significantly enhance the surface quality in SLA prints, potentially eliminating the need for secondary finishing processes. The implications are relevant to both industrial and medical applications where dimensional fidelity and surface smoothness are critical. Recommendations for optimal washing durations are proposed for each material, and directions for further research are outlined.