The following figure shows how to make a pole and tube for this robot. Again, this design is all up to you. You can design customized poles too:
Figure 2: Pole and tube dimension of the robot
From the preceding figure, you can see the dimension of the pole and tube. It's 3.5 cm by 1.4 cm. The poles that we've used here are basically hard plastic. We are using hollow tubes to connect to the poles and extend them for the second layer. The length of the hollow tube is 15 cm, and it has a slightly bigger diameter than the poles, that is, 1.5 cm. Only then will we be able to insert this tube into the pole. A hard plastic piece is inserted at one side of the hollow tube, which helps connect the next layer.