Print a Leg

Posted on October 4, 2020

First things first: we got a logo. This logo should represent Berlin, football, robotics, electronics, lasers, AI, …, but it also had to be simple. Which is why we asked someone who actually knows a bit about logo design.

We agreed on this logo:

Now all we need is a robot. Our goal is to design an easily reproducible and cheap robot that is able to participate in the Humanoid League of the RoboCup. We strive to contest in the Kidsize league, that means our robots will be 90-100cm high. (That is equal to the size of a two year old child.)

Thanks to our experience with robotics we can and want to avoid known pitfalls. We want to reduce the stress applied on the axles of the motors. By driving the joint indirectly (for example with timing belts, push rods or bevel gears), the skew force is not transmitted from the joint to the motor. This reduces the stress on the motors and will improve the longevity of the parts. In the case of the knee it will avoid skew of the leg and thereby improve proper movement under load. We challenge ourselves to design accessible parts that are cost-efficient. This will be accomplished by 3D printing the casing of the robot.

Our design started with a simple 3D CAD model found on GrabCAD. Micha and Lutz worked tirelessly on the design of our first-generation robots' legs. They took the 3D model and added space for screws, joints, electronics, and motors. After ~24hrs of printing, this is the result:

The 3D printing of all the parts was done on an Artillery Genius printer using simple PLA. The leg is 30cm high and weighs 580g. It consists of seven parts and is held together by 41 M3*10 screws. We are quite pleased with the result of our 3D print. It remains to be seen if the plastic will withstand the mechanical stress and the heat of the motors. We are quite optimistic it will work.

The leg is easy in comparison to the hip joint that we are working on right now. The hip is probably one of the hardest parts of the robots. We will keep you posted via this blog. If you have any questions about our design contact us via or join our Matrix Channel