Beyond lifetime testing: Time-resolved wear and failure analysis of additively manufactured gears

In this work, a gear test rig developed for additively manufactured (AM) gears with continuous wear measurement is presented, and its capabilities are demonstrated through application-oriented experimental studies. The test rig enables time-resolved measurement of tooth flank wear, torque, and both ambient and surface temperature, thereby providing direct insight into damage progression during operation. Defined operating conditions can be precisely controlled through additional instrumentation and extension modules, including contactless directional temperature measurement, software-based termination criteria, and optional thermal and lubrication modules. This allows individual damage mechanisms to be investigated reproducibly and with high temporal resolution. To validate the testing concept, experimental series were conducted using AM gears manufactured from Polylactic Acid (PLA) and Acrylonitrile Butadiene Styrene (ABS). The results revealed pronounced material-dependent wear and failure mechanisms that differed both between the investigated materials and from those commonly observed in conventionally manufactured polymer and metal gears. While ABS was primarily characterized by crack-induced tooth and partial-tooth fracture, the behavior of PLA was dominated by complex thermally driven processes, including creep, material displacement along the tooth flank, deformation, peeling, and abrasion. The investigations showed that AM gears require a nuanced analysis due to their anisotropic material properties, limited geometric accuracy, and strongly temperature-dependent material behavior, which evolves throughout the service life. Furthermore, the tooth flank geometry changes continuously during operation as a result of wear, deformation, and material displacement. By combining continuous wear measurement with time-resolved surface temperature monitoring under controlled operating conditions, the proposed testing concept enables detailed investigation of wear and failure processes and provides a robust experimental framework for the development and validation of future design approaches for AM gears.