Hollow-Shaft Cable Routing

Routing cables through the center bore of a joint's motor and reducer instead of along the outside.

In hollow-shaft cable routing, a joint module's motor rotor, reducer, and encoder are all built with a hollow structure, leaving a through-hole in the center for power, data, and pneumatic lines to pass from inside one joint straight to the next, instead of hanging on the outside. The benefit is a cleaner look, cables that can't get tangled or snagged, and a lower risk of catching on a person's hand — important for collaborative arms and humanoid robots that work close to people. The trade-off is that the motor and reducer have to be built a size larger, and the bore diameter and cable bend life have to be designed together; the cable also twists as the joint rotates, which puts an upper limit on the joint's rotation angle. Applications that need unlimited rotation use a slip ring instead. The “hollow-shaft” variants commonly offered for harmonic drives exist for exactly this purpose.

ExampleMany collaborative robot arms show no visible cables on the outside at all, because every cable is routed through the center bore of each joint.

Also called

Hollow-Shaft Wiring, Internal Cable Routing

Related

Joint Actuator Module · Wire Harness · Slip Ring · Strain Wave Gear (Harmonic Drive) · Frameless Torque Motor

Sources

Slip ring - Wikipedia