What Is an Emergency Stop? E-Stop Systems in Industrial Robotics.

What Is an Emergency Stop?

An emergency stop, commonly called an E-stop, is a manually initiated safety function intended to stop a hazardous machine operation in an emergency.

Emergency stops are commonly activated using prominent pushbuttons or other designated controls.

In robotics, an emergency stop provides a way for an operator or another person to initiate a stop when an immediate hazard is recognized.

For example, a worker who sees a robotic machine behaving dangerously may activate an emergency-stop device to initiate the system's designed stopping response.

Key Takeaways

• Emergency stops provide a manually initiated way to stop hazardous machine operation.
• An emergency stop is a complementary protective measure, not a replacement for guarding or other risk-reduction measures.
• Resetting an emergency-stop device should not automatically restart hazardous machine motion.

How Does an Emergency Stop Work?

An emergency-stop device is connected to a safety-related control system.

When activated, it triggers a predefined stopping function.

Depending on the machine and its risk assessment, the system may remove actuator power immediately or perform a controlled stop before removing power.

The appropriate stopping behavior depends on the hazards.

For example, abruptly removing power from a vertical robotic arm could allow a suspended load to fall if the mechanism lacks suitable holding provisions.

A controlled stopping arrangement may therefore be necessary for certain machines.

The emergency-stop function must be designed as part of the complete safety system.

Emergency Stop vs. Normal Stop

A normal stop is used during routine machine operation.

For example, a factory operator may stop a production line at the end of a shift.

An emergency stop is intended for situations requiring a rapid response to an immediate or developing hazard.

It is not intended to replace normal operating controls.

Regularly using an emergency stop as a routine production stop may also be inappropriate for the system's intended design.

Does an Emergency Stop Make a Robot Safe?

Not by itself.

A worker should not have to recognize and react to every dangerous movement before an accident occurs.

Physical guarding, interlocks, protective sensing, and other measures may be required to reduce hazards before they occur.

Emergency stops provide an additional protective function.

The appropriate arrangement depends on a risk assessment and applicable standards.

What Happens After an E-Stop Is Pressed?

The machine must enter its designed stopped condition.

The cause of the emergency must then be addressed.

Resetting the emergency-stop device releases the stop command, but should not automatically restart hazardous operation.

A separate intentional action should be required to restart the machine under appropriate conditions.

Frequently Asked Questions

Does pressing an emergency stop always remove electrical power immediately?

No. Different stopping functions may be used depending on the equipment and safety requirements.

Is an E-stop a replacement for a safety fence?

No. Emergency stops are complementary protective measures and do not replace required safeguards.

The Bottom Line

Emergency stops provide an important means of responding to hazardous machine operation. They must be designed around the equipment's risks and used alongside other appropriate safety measures.