One of the biggest complaints we hear from our powder brethren is consternation around build plates: Parts can crack and delaminate from the build plate during printing often undetected since the part is buried in powder. Build plate bolts can break from excess residual stress during a build. A failed understanding of how stress accumulation around individual parts during a build leads to the distorted final parts. During one such conversation, someone wondered “How can we measure the loads going through the build plate?” That conversation led to a team being assembled to build an instrumented PBF build plate for the Defense Logistics Agency (DLA) under a Phase I STTR. Ultrasonic additive manufacturing (UMA) was chosen to print a plate with a single embedded fiber optic sensor. UAM is unique in that the solid-state welding technology allows embedding sensors into metal parts. A fiber optic was embedded with a specific undulating pattern that allowed resolving the strain across the entire build plate. The team put the smart baseplate in a LPBF machine and attempted a build that included "problematic" features. From this initial build the team found that the device picked up a significant amount of data: Resolution/scan rate were high enough to discern the scan strategy by layer; defects were measured as large compressive strains forming early in the build at localized points; and a slow delamination was seen in the data although the recoater blade never contacted the delaminating feature.
- Discuss how sensors can be embedded in 3D metal parts
- Describe strain evolution in a LPBF baseplate
Conduct analysis of baseplate strain data to indicate flaws