What the slip ring has to handle
- Unlimited (beyond 360 degrees) rotation at the tool interface without cable wind-up
- Industrial Ethernet and fieldbus channels (e.g. PROFINET, EtherCAT-type real-time networks) alongside load and sensor circuits
- Low-voltage tool power, typically tens of volts and a few amps
- Very short axial length and low mass to preserve payload, often a pancake format
- Pneumatic or vacuum passages combined with electrical rings (electro-pneumatic unit)
- Wide operating temperature and maintenance-free operation for continuous production
- Option for an integrated encoder for secondary position feedback
Typical figures
| Circuits | Example robot pancake ring: up to 20 channels for fieldbus/Industrial Ethernet, load and signal |
|---|---|
| Current | Up to 5 A at 60 V AC or 48 V DC (example pancake ring) |
| Size | 160 mm diameter, installation depth from 10 mm (example pancake ring) |
| Temperature | -40 C to +75 C (example pancake ring) |
| Pneumatics | Combined units with 8 pneumatic channels used on cobot screwdriving tools |
Example figures from the published sources listed below. Your requirement may differ; an engineer will confirm against your duty cycle.
Recommended slip ring types
Standards to consider
- ISO 10218-1 / ISO 10218-2 - safety requirements for industrial robots and robot systems
- ISO/TS 15066 - collaborative robot operation (relevant to cobot end-effectors)
- IEC 60204-1 - electrical equipment of machines
The complete system
A slip ring rarely works alone. For robotics & robot wrists it is usually specified together with:
- frameless torque motor
- harmonic or strain-wave gearbox
- absolute encoder
- servo drive
- holding brake
- tool changer
Specifying these together avoids mismatched connectors, cable routes and feedback interfaces, and gives you one point of contact for the whole axis.
Common problems to design out
- Dropped packets or fieldbus errors from contact noise on Ethernet rings
- Brush wear from high cycle counts at the wrist
- Leaks in combined pneumatic passages
- Cable strain at lead exits from repeated arm motion
Series used in this application
Frequently asked questions
Can a slip ring carry PROFINET or EtherCAT to a robot tool?
Yes. Robot-wrist slip rings are built with industrial Ethernet and fieldbus channels separate from load and signal rings. Published cobot tools pass PROFINET through the slip ring for continuous monitoring during screwdriving.
Why use a pancake slip ring on a robot?
Pancake rings put the tracks on flat boards rather than a long drum, so installation depth can be as little as around 10 mm. That saves length and mass at the wrist, which matters on low-payload robots.
Can air and electrical signals be combined at the robot wrist?
Yes. Combined units pair a rotary union with an electrical slip ring so pneumatic or vacuum lines and electrical channels pass through the same rotating joint. Eight-channel pneumatic combinations are used for multi-step clamping on cobots.