Analysis of 3D-Printed Cycloidal Gear Degradation in a Run-to-Failure Test

The paper presents results of a degradation analysis of polyamide 12 reinforced with carbon fibers used for additive manufacturing of cycloidal gear. Both FEM simulation and a fatigue test indicated the ability of the material to withstand loads during the work of cycloidal transmission. However, a run-to-failure (RTF) test revealed critical failure after 105 cycles, with displacement and damage of the material in the area close to bearing instead of expected areas of teeth being in friction with pins. Acceleration analysis with time synchronous averaging (TSA) confirmed rapid degradation of the material’s strength at the end of the RTF test. It was found that the PA12 cycloidal gear damage was a result of fatigue accelerated by the temperature increase under the cyclic loads that took place during the RTF test. In particular, displacement of 0.2 mm did not appear in the specimens tested at 27 °C even after 105 cycles, while at 140 °C this value was reached almost immediately. At 70 °C and 90 °C, plastic deformation of 0.2 mm was reached after 30,000 and 5000 cycles, respectively. The finding can be used in a predictive maintenance system of such cycloidal transmission with 3D-printed polymer gears.