I designed this actuator in SolidWorks and 3D printed the plastic components. It uses a two-stage timing belt reduction to provide the motor mechanical advantage. It has at least 3.6 Nm of dynamic torque running at approximately 1.8A.
As shown in the no-load precision test, the actuator is capable of sub-millimeter precision with a 0.55m lever arm.
The first stage is a 5:1 reduction, and the second stage is 3:1. Each stage uses a 200mm loop of GT2 timing belt. Generating sufficient belt tension in the second stage was the largest challenge. I settled on using an adjustable idler bearing, which can be seen in some of the images.
