Asteroid gear has compact structure and high reliability. It is usually used for reducing transmission in industrial fields (rotary, walking, winch, etc.). Because of its high power density, it can achieve small volume and large speed ratio, so it can realize the rapid increase of torque for driving the next level components. Because of the above advantages, asteroid gear has been widely used in the field of wind power yaw and pitch. However, a kind of special failure mode appeared in the early stage of asteroid gear, that is, the planetary pin shaft emerged. The emerging pin shaft butted the upper planetary carrier, hindered the rotation and scraped a large number of cast iron filings, which further caused lubricating oil pollution, bearing failure and high maintenance cost. It will introduce the whole process of the author’s participation in the problem analysis, the determination of the root cause and the final corrective measures.

Through the brief analysis of the pin failure cases in the planetary structure, it is found that it is necessary to make full simulation calculation in the design stage of structural parts. However, simulation calculation is theoretical calculation under certain assumptions, preconditions and simplified conditions. Engineers can not just regard these factors in calculation as default preconditions of software, but need to pay special attention to these conditions, because the correctness of calculation results is precisely based on the correctness of preconditions and other factors. If the premise is not correct enough, the result is not completely convincing. Sometimes design can’t do without the correction of life experience to theory.

The case analysis comes from the application experience of the author’s own industry. According to the similarity of working conditions, it can be used as the experience reference in the field of planetary transmission under similar working conditions to a certain extent.