Assessment of Post-printing Component Cleaning Solutions for Lithography-based Metal Additive Manufacturing

Abstract

Additive Manufacturing (AM) enables the production of highly detailed components with complex internal geometries difficult to manufacture conventionally. Lithography-based Metal Manufacturing (LMM) is one such novel AM method, and the subject of investigation of this thesis. Post-processing of LMM components with internal features smaller than 1.5mm presents significant cleaning challenges. During de-caking, heat is applied to liquefy and drain excess feedstock. However, capillary forces and surface films trap viscous excess feedstock within internal features, making removal difficult. The current cleaning procedure produces defects and lacks standardization. This thesis aims to develop a standardized post-processing method minimizing cleaning-induced defects and yielding reliable cleaning results. Ten batches of stainless steel 316L test components containing channels, junctions, and narrow fin arrays were manufactured and cleaned iteratively to identify defect-causing parameters. These parameters were validated through additional batches to establish a complete cleaning procedure. Mechanical and chemical agitation proved most effective for feedstock removal. The optimal method involved inverted printing to avoid flow restrictions caused by the build plate, followed by a 15-minute de-caking stage and intermittent cleaning cycles using pressurized air and heated proprietary solution IncuSOL. A final 60 second exposure to the ultrasonic bath in heated IncuSOL is used to clear residual feedstock from components. Since polymerization begins immediately after printing and is accelerated by heat, cleaning must start directly after the print, conclude within 30 minutes, with the heating temperature limited to 60 ◦C. Using this method, straight internal channels as small as 0.8mm in diameter and 5mm in length were successfully cleared. Further research is required to evaluate process consistency for other materials.