Hi everyone!

In the previous post i improved accuracy adding a belt to the shoulder and it worked fine, but this way I couldn't apply force to both direcctions, so I decided to make a printed gears.

After design and some quick calculation this is the result. In fact this new assembly make posible that the arm can be dismounted by removing the two pieces that are above the axis to transport it easier.

Here's a video of how they work:

Now I'm thinking about how to add a spring to help to lift the arm, it would be something like the following image.

See you soon!