Method for a reliable and cost-efficient coordinate system transfer process for machining wire arc additively manufactured parts

Wire arc additive manufacturing (WAAM) is a process known for its material-saving benefits. However, it requires subsequent post-processing, e.g., machining, due to the low surface quality and form inaccuracies of the workpieces. The additive-subtractive process chain includes the coordinate system transfer process (CSTP), during which the position and the shape of the WAAM parts are determined for the subsequent machining process. Especially for more complex parts with shape variations such as WAAM parts, the CSTP is either very time-consuming or can lead to processing errors. In this paper, a WAAM specimen with target geometry was developed, which incorporates several geometric features. The test specimen was machined using two different state-of-the-art CSTP methods, a conventional (only tactile probing) and the fiducial-based (digitization and tactile probing) one. Comparing the final geometries of the produced workpieces revealed that the conventional CTSP leads to machining errors, while the fiducial-based method leads to a nearly accurately produced part. This also shows that the designed test specimen is suitable for comparing different CSTPs with each other, but also the need for further research. Thus, this paper proposes a novel method for a reliable and cost-efficient CSTP, specifically for the shape accurate machining of WAAM parts. The method considers data of different origins, including WAAM process data, optical data, synthetic data, and tactile probing data. First, a digital model of the WAAM part is built cost-efficiently. Then, tactile probing on the determined measurement points is executed, and a key indicator is derived, which ensures that the CSTP and therefore the machined part is accurate. In future work, the proposed method for a reliable and cost-efficient CSTP will be implemented as well as validated regarding the specimen developed.