Methods and procedures for a long-term additive manufacturing metrology study

Hornung, Skylar Laura
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Most additive manufacturing metrology studies focus on individual prints to characterize or optimize a given process, but there is a lack of publicly available metrology data collected over a series of builds over time. Long-term metrology studies continually monitor the performance of a machine to track changes in the machine’s output. The goal of this study is to support future long-term metrology studies for direct metal laser sintering (DMLS), stereolithography (SLA), and material jetting (MJ) processes, each of which are used by The University of Texas at Austin’s Center for Additive Manufacturing and Design Innovation (CAMDI).

This thesis proposes a new dimensional metrology artifact, a measurement fixture compatible with a coordinate measuring machine (CMM), a measurement program for the CMM, and a database. The proposed metrology artifact includes features that test dimensional and form accuracy for raised and embedded features with square and circular cross-sections. This artifact is small enough to unobtrusively fit into regular unrelated builds without consuming excessive material or extending build times. The accompanying measurement fixture holds each artifact in the same position on the CMM table to reduce user intervention in the CMM’s base alignment process, prevent the artifact from moving when prodded by the CMM’s contact probe, and allow easy artifact insertion and removal. The measurement program enables the fast, precise, and automatic measurement of each specimen. The database reports statistics for each characteristic measured. To explore the results in the database, the user supplies the date range of tests to include in the analysis and flags a test to compare to the historical data.

The paper concludes with a small metrology study from multiple artifact copies printed in a single material on each of CAMDI’s machines to verify the utility of the artifact for each additive manufacturing process. The paper explores the database’s output to find each machine’s tendencies. The results indicate that the proposed artifact, fixture, measurement procedure, and database will be useful tools to monitor each machine in a future long-term metrology study.