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Maintaining Grip During Emergency Stop with E‑Pick

Ensure continuous vacuum power to prevent part drop–even during power loss or E‑Stops.

Context

When using the E‑Pick vacuum gripper, an emergency stop (E‑Stop) can interrupt the vacuum supply, causing the gripped object to fall. This presents risks to part integrity, operator safety, and equipment reliability—especially if the gripper is powered through the robot’s wrist via an I/O Coupling.

This article explains how to ensure the vacuum is maintained even during an E‑Stop by using the correct power setup.

 

1. What Happens During an E‑Stop?

When a UR robot triggers an E‑Stop, it immediately cuts off power to non-essential systems—especially the 24 V supply at the wrist connector. If your E‑Pick is powered through this port, the vacuum is lost, and the object will fall.

This issue is especially relevant when using:

  • Wrist-mounted I/O Coupling

  • No backup power source

 

 

2. Use Controller Power to Maintain Vacuum

If your E‑Pick is connected directly to the robot controller’s digital output using a cable:

  • The gripper continues to receive 24 V power even during an E‑Stop.

  • Vacuum is maintained.

  • The object stays safely in place.

This method is simple and robust—but may require longer cabling.

 

3. Issue with Wrist-Mounted

If your gripper is powered through the I/O Coupling or E-Series Coupling at the robot wrist:

  • The 24 V power is cut off during an E‑Stop.

  • The E‑Pick immediately loses vacuum.

  • The object falls as soon as the stop is triggered.

This behavior is inherent to the robot controller’s emergency safety logic.

 

4. Recommended Solution: Use a UPS

To prevent part drops when using the I/O Coupling:

  • Connect the E‑Pick to an uninterruptible power supply (UPS).

  • This keeps the gripper powered even when the robot controller shuts off the wrist 24 V.

  • Vacuum is maintained long enough to safely manage the situation or recover the system.

UPS must supply 24 V DC and be correctly sized for the E‑Pick’s current draw.

 

5. Additional Design Tips

  • Use mechanical supports: Where possible, design the end-effector or part nest to provide passive holding in case of vacuum failure.

  • Program safe stop behavior: Consider adding UR logic that detects an E‑Stop and prepares the robot or gripper accordingly (where permitted).

  • Test under E‑Stop: Validate the behavior during commissioning with actual parts to ensure safe handling in real events.

 

Conclusion

To avoid dropped parts during an emergency stop:

  • Avoid relying on wrist-mounted power alone.

  • Use direct controller power or a UPS to maintain vacuum pressure.

  • Consider adding passive retention or UR programming logic as secondary safety measures.