Slip Rings for Robotics and Rotary Tables
A seventh axis, a tool changer or an index table all ask the same question: how do power and signals cross a joint that turns forever? The answer is a slip ring sized to the wrist — not to the robot.
Key specifications
Specifications
| Parameter | Value | Notes |
|---|---|---|
| Bore options | 12.7 / 25.4 / 38.1 / 50 mm | Match the axis shaft, not the robot payload |
| Circuit count | 2 – 36 | Tool power, I/O, fieldbus, encoder |
| Current per ring | 5 A / 10 A / 20 A | Parallel rings for tool power above 20 A |
| Voltage | 440 V | Dielectric strength 800 VAC (power) |
| Rotation speed | Up to 250 rpm | Index tables and positioners run well within this |
| Life expectancy | 20 / 50 / 80 million revolutions | High-cycle tool changers need the top tier |
| Operating temperature | −30 to +80 °C | Welding cells need headroom |
| Protection class | IP51 / IP65 / IP68 | IP65 for machining and welding environments |
| Contact material | Six-element alloy wire, gold plated | Low noise for fieldbus and encoder signals |
Where they are used
- Robot seventh axis — travel axis power and signals across a rotating joint
- Tool changers — power, air and I/O at the wrist
- CNC rotary and index tables — servo power and encoder feedback
- Positioners and turntables — welding positioners, assembly carousels
- End-effector rotation — continuous rotation instead of a cable loop
The three mistakes that kill robot slip rings
- Sizing by robot payload instead of axis shaft — a 200 kg robot may have a 30 mm wrist shaft. The bore follows the shaft, not the payload chart.
- Running a cable loop “for now” — a dress pack that twists through 540° per cycle fails at the conductor, usually inside the cable, where it is hard to find. If the axis truly rotates continuously, a slip ring is the only durable answer.
- Ignoring fieldbus requirements — EtherCAT, PROFINET and CAN need controlled impedance and shielding. A power-grade ring will carry the voltage but will not preserve the signal.
Specification shortcut
- Shaft diameter at the rotating joint — this sets the bore class.
- Circuit list — tool power (A), I/O count, fieldbus type, encoder type.
- Rotations per cycle and cycles per shift — this sets the life tier.
- Environment — coolant, weld spatter, dust; IP class follows.
Frequently asked questions
Can a slip ring pass EtherCAT or PROFINET?
It can, but only with a signal-grade arrangement: controlled impedance, shielding and dedicated ring groups. Tell us the protocol and data rate — a standard power ring will not preserve the signal.
How many rotations can a tool changer do before service?
With the 80-million-revolution tier and gold-plated contacts, a high-cycle changer runs for years without contact service. The bearing and seal are the parts to watch.
Do I need a separate rotary union for air?
Not necessarily — gas-electric units combine both in one housing. If air pressure is moderate and the port size fits, one unit is simpler and cheaper than two.
What if the axis only turns 300 degrees?
Then a cable loop may still be viable. A slip ring is justified when rotation is continuous or exceeds what a dress pack can absorb over the machine life.
Related products
- 25.4 mm bore series — the common robot and table size
- 12.7 mm bore series — compact wrist and small tables
- 50 mm bore series — large positioners
- All through-bore slip rings
Specifying a slip ring for a robot or rotary table?
Send the shaft diameter, circuit list and cycle rate — you will get a technical recommendation, usually within 5 hours.
