For the series connection of joints, the 4 draw wires of the second (or upper) joint should be conducted through the first (or lower) joint. This feedthrough must be done in such a way that a movement of the lower joint does not alter the wire lengths of the feedthrough, which means Bowden cables are needed.
In the pictures you can see the schematic and actual feedthrough of the 4 draw wires by means of igus® plastic Bowden cables.
In the connecting rods of the joints (“skeleton”), the wires and cables are free in contrast. In total, a maximum of the following elements can be routed through an RL-50 joint:
4 draw wires plus 2 sensor cables (joint 1 and 2) plus 2 additional cables max. d4 (compressed air or electric).