Abstract: Causes of contact fatigue failure of the cycloidal and planetary gears in joint reducer for robot during the life test were studied by means of physical and chemical testing and finite element stress analysis. The results show that the failure mode of cycloidal gear surface is scuffing, and the failure mode of planetary gear surface is excessive wear. The design values of contact fatigue strength of cycloidal gear and planetary gear face meet the technical requirements, and the materials used meet the specification. According to the results of metallographic examination, the surface heat treatment performance of planetary gear does not meet the requirements, and the reduction in the hardness of gear surface and contact fatigue strength becomes the main reason for the failure of planetary gear. Based on the analysis results, the improvement measures for the subsequent manufacturing process of planetary gear are put forward.

Key words: life test, gear, wear and scuffing, heat treatment