The effect of gear-manufacturing quality on the mechanical and thermal responses of a polymer-gear pair

Gear-manufacturing quality affects the load sharing between the meshing gears as well as the load distribution along the width of the tooth. This study aims to investigate the effect of gear-manufacturing quality on the mechanical and thermal states of polymer-gear pairs and consequently on their lifetime. The deviations of the geometric quality parameters, i.e., the lead profile and pitch, were found to have a substantial effect on the stress (root and flank) state of the gear. The effect of the lead deviation was found to be most pronounced for the quality grades Q12 to Q10, where depending on the load, a 30–80% stress reduction was observed when improving the gear quality from Q12 to Q10. Improving the quality from Q10 to Q8 did not lead to a substantial improvement in the load distribution and the observed stress reduction was in range of 5–20%. Similar trends were found for the pitch deviation, where again the most pronounced stress reduction was seen when improving the quality grade from Q12 to Q10. The study reveals where the most effective changes, leading to an increased gear-life, can be achieved. Improving the gear quality grade from Q12 to Q11 proved to have a much more substantial effect than improving the gear quality from Q9 to Q8. Considering that improving the gear quality from Q12 to Q11 or even Q10 can be achieved by a proper tool design and corrective iterations with the right process parameters, while improving the quality from Q9 to Q8 is by far more challenging. A novel methodology is proposed to assess the effect of the gear's quality on the generation of heat and the resulting operational temperature. The proposed methodology enables more accurate prediction of the gear pair's operating temperature.