Effect of rotational speed on the performance of unreinforced and glass fiber reinforced Nylon 6 spur gears

Polymer gears used in power and motion transmission work under different loads and speeds. Mechanical properties of the polymers are severely influenced by the loading rate compared with the metals. The gear rotational speed decides the loading frequency of the polymer gear tooth, which influences the temperature generated and thereby the strength of the material. Performance of polymer base gears at different gear rotational speeds is reported in this paper. Injection molded unreinforced Nylon 6 and 20% short glass fiber reinforced Nylon 6 spur gears were tested at various speeds and torque levels in a power absorption type gear test rig. Gear rotational speed affects the performance of gears made of both the materials at high running speeds and high test torques and not in low speeds and torque levels. On-line measurement of test gear surface temperature and failure analysis was done to understand the failure mechanisms. At all the investigated gear speeds, glass fiber reinforced Nylon 6 gears shows superior performance over unreinforced Nylon 6 gears due its superior mechanical strength and resistance to thermal deformation.