4DoF mini robot arm

The robot was designed to use sg90 servo motors, and to be controlled via rosserial.
Since the scope of the project only considered its movement, it doesn't have an end effector. However, if you like, you can print any, as the last link (link 4), is completely flat.
To mount the complete robot, you need 3 screws per servomotor. That shouldn't be a problem, since these motors come with said screws.
For the construction, you need two pairs of the link 2 pieces (link 2 a & link 2 b). It is also possible to keep adding link 2s to get more degrees of freedom and length, but due to the form of the arm and the strength of sg90 servos, I don't think surpassing the original 4 DoF would be a good idea.