Influence of Wear and Thermal Deformation on Machined PEEK Plastic Bush and Ti Crank Shaft

In biped walking humanoid robot, toughness, durability and lightweight of joint parts are crucial factors due to parts’ constant exposure to high torque and loads. Such ergonomically challenging conditions create the need for joint systems comprising independent elements capable of keeping the component operable for long periods of time. In our work, we focused on wear and thermal deformation in two different grades of both poly-ether-ether-ketone (PEEK) and polyoxymethylene (POM) plastic bushes. The components used for investigation were bushes typically employed in speed reduction devices in joint models for biped walking humanoid robots. In such joint systems, plastic bushes are directly connected to a crankshaft, playing an important role in the robot's movement ability. In order to acquire the knowledge of how to build more efficient systems, the influence of the titanium crankshaft roughness on the frictional heat occurring between the shaft and the polymer bush as well as the input axis-output axis backlash require close examination. Based on Rolling Contact Fatigue test, we established the optimal machining conditions for the crank shafts and bushes. Also, superior to other tested polymers as far as glass transition temperature, wear toughness and thermal deformation are concerned, PEEK was found to be the best suiting material for our investigation.