Mechanical Design
Hollow-Shaft vs. Solid-Core Sensors: Cable Routing Architectures
Ask any maintenance engineer what kills robot uptime, and the answer is rarely software. It's cables. Specifically, cables at the wrist that get twisted, pinched, and abraded until they fail. Your choice of sensor architecture—hollow shaft or solid core—determines how bad this problem gets.
A Typical Wrist Setup
Picture a real-world end effector: pneumatic gripper, 2D vision camera, maybe a laser distance sensor. That's two pneumatic lines, 24V power, Gigabit Ethernet for the camera, and discrete I/O for the valve block. Five or six cables before you even count the force sensor itself.
With a solid-core sensor sitting between the flange and the tool, every one of those cables has to route around the outside of the sensor body. When Axis 6 rotates—which it does constantly in a pick-and-place cycle—those cables twist, rub against the housing, and accumulate fatigue. Give it a few hundred thousand cycles and something breaks.
Routing Through the Center
A hollow-shaft sensor has a bore machined straight through the measuring body. Instead of routing cables around the sensor, you thread them through it—right along the rotational axis of Axis 6.
This matters because cables on the center axis of rotation experience minimal torsional stress. They're not being stretched across a wide radius. The bend is symmetric, the stress is distributed, and cable life goes up by an order of magnitude in continuous-rotation applications.
The AXIOM-HS has a bore large enough to pass standard M12 and RJ45 connectors without disassembly. During a tool change, you pull the whole assembly—sensor, cables, and tool—as one unit.
When Solid-Core Makes Sense
Hollow-shaft sensors sacrifice some structural material to create the bore. A solid core handles higher axial loads (Fz) and bending moments (Mx, My) for the same outer diameter because there's more material working in the load path. Overload ratings tend to be higher, and cross-talk tends to be slightly lower.
If your tool is simple—a suction cup, a probe, a single pneumatic line—routing isn't a problem. In that case, a standard AXIOM gives you better structural margins in a more compact package.
Cable failures are predictable, preventable, and expensive. Choosing the right sensor geometry is the cheapest reliability upgrade you can make at the wrist.