Guide · Updated June 11, 2026
What happens to the part during a power loss?
A power cut or emergency stop should never drop a part. This guide explains how different grippers behave when power is lost, and why a mechanical hold is the safe choice.
Power loss is not a rare edge case — it includes every emergency stop, every tripped breaker, every planned shutdown. What the gripper does in that instant decides whether you have a safe stop or a dropped, damaged, or dangerous part.
How different grippers behave
| Gripper type | Behaviour on power/air loss |
|---|---|
| Pneumatic (no check valve) | May open as pressure falls — part can drop |
| Pneumatic (with check valve) | Holds briefly, until pressure bleeds off |
| Motor-held electric | Holds only while current is maintained |
| Spring-closed | Holds, but force is fixed and often limited |
| Mechanically self-locking (Servo-Flex) | Holds indefinitely with no power or air |
Why a mechanical hold is the safe choice
Servo-Flex locks its clamping force through the mechanism itself. Once closed, the jaws stay clamped whether or not the gripper has power. That means:
- an emergency stop never drops the part;
- a power cut overnight does not scatter parts on the floor;
- unattended and collaborative operation stays safe by design.
Designing for the worst moment
Good cell design assumes power will be lost at the worst possible time — mid-motion, part in hand. A gripper that holds mechanically turns that moment into a non-event. It is also one less hazard to mitigate in your risk assessment.
The takeaway
If your cell runs unattended, lifts heavy or hazardous parts, or shares space with people, the gripper's power-loss behaviour is a safety decision, not a detail. Learn how Servo-Flex achieves it on the technology page.