Fault Phenomenon: Co-Nele KNL5600 safety functions are normal when cold. After an emergency stop (operating temperature), the emergency stop button fails and cannot be reset, posing a danger.

Troubleshooting Process:
– Checked emergency stop button: button mechanical structure normal, no seizing.
– Checked emergency stop circuit: circuit continuity normal, no open circuit.
– Checked safety relay: relay engages normally, no fault.
– Measured emergency stop circuit resistance at operating temperature: found infinite circuit resistance.

Root Cause: Internal contacts of the emergency stop button melt and stick due to heat, preventing it from opening.

Required Parts: Emergency stop button assembly.