Post-processing Additively Manufactured Parts with CNC Milling : Fixturing Solutions

Abstract

This thesis investigates fixturing solutions for CNC milling of aluminum parts manufactured by Laser Powder Bed Fusion (LPBF), addressing the challenges posed by complex geometries and dimensional deviations inherent to additive manufacturing. Three distinct fixturing methods were developed and applied: a machined bolt-on jig, additively manufactured polymer counterparts, and integrated fixturing interfaces designed directly into a part. A case study was carried out using test parts: a Vacuum Chamber, a Vacuum Gripper Tool, and a Cell Leg. 3D scanning and caliper measurements were taken before and after milling to check accuracy and stability. Results demonstrate that all three fixturing solutions were effective in securing LPBF parts during machining. The bolt-on jig provided the highest dimensional accuracy and angular stability due to its rigidity and precise contact surfaces. Additively manufactured fixturing offered geometry-specific interfaces and cost benefits but showed slightly increased deviations, primarily due to surface roughness from the LPBF process. Integrated fixturing features exhibited the largest deviations, likely caused by yielding during machining, indicating that further design optimization is needed. The findings highlight a trade-off between cost, lead time, and accuracy when selecting fixturing methods. While traditional machined fixtures excel in precision, additively manufactured fixturing solutions present viable alternatives for customized and cost-effective setups especially when production time allows. Ultimately, fixturing method selection depends heavily on the specific part and should consider part geometry, process requirements, and resource constraints.