Elbow.scad A parametric elbow or simple shoulder joint.It will allow you to hide wires etc. inside the mechanism, making the arm appear very simple, while the underlying system may be quite complex.Change the parameters to match the support pipe to the PVC or other piping you will use for the arm sections. The support pipe has 3mm thick walls, so the inner diameter should be 6mm less than the outerPrint two for each elbow joint. Use two 608 bearings and place in the bearing recesses in the one half of the joint, and secure the other half to the 8mm threaded rod using 20mm washers in the bearing recesses.