🦾 Nina Mao | UW Mechanical Engineering

In Husky Robotics, we have historically used a differential gear system for our wrist joint. It's a compact method of driving 2 degrees of freedom, and we've found that a full 6-DOF arm is critical for our competitions. However, our previous differential wrists used 3D printed PETG or carbon fiber-filled PLA for the driveshafts and gears, which proved problematic with extended usage—a lack of stiffness caused the teeth to easily slip due to the high axial forces of the miter gears, the surfaces with supports were difficult to smooth which caused nonconstant asymmetrical motion between the 2 side gears, and the driveshaft failed due to fatigue during competition.

 

By upgrading to steel miter gears, aluminum driveshafts, and brushless motors and adding bronze bushings (rather than the previous plastic on plastic joints), we were able to significantly upgrade our operation, longevity, and strength while simultaneously reducing our overall footprint and weight (even after the switch from plastic to steel gears)!

 

We also focused heavily on improving the manufacturability of the wrist by ensuring all machined parts were easily clamped and limited to 2D shapes that could be waterjet when possible as well as mounting the gearboxes to the back plate rather than the sides for easier assembly.

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This was my first project at Husky Robotics after stepping down from Arm Subsystem Lead (due to becoming a Master's student) and 2 internships. With my increased experience compared to my previous robotics projects, I was able to guide the other members on my team and create a much more thoughtful and robust design!