By Dovydas Kersys · Chapter 27 of 58 in Machine Commissioning.
Before you begin: Follow the machine documentation, risk assessment, site procedures and lockout/tagout requirements. Commissioning can expose personnel to electrical energy, stored pressure and unexpected motion. Never defeat a safety function merely to make a test easier. Examples and diagrams are generic and must be checked against the actual machine.
Machines use different stop behaviors for normal stop, emergency stop, guard opening, controlled stop and power loss. Commissioning must prove the intended deceleration and final safe state.
Why this matters during commissioning
A stop that is too aggressive may trip drives or spill product; a stop that is too slow may violate process or safety requirements.
Commissioning procedure
- Identify stop categories/modes defined by the risk assessment and machine design.
- Measure or observe stopping behavior at low and then representative speed.
- Verify mechanical brakes, drive braking resistors and controlled deceleration where used.
- Confirm stop commands override production commands.
- Test restart behavior after each stop type.
Common failure patterns
- Normal stop and emergency stop use the same uncontrolled behavior even though design calls for different responses.
- Drive deceleration causes overvoltage trip.
- Brake applies before speed reaches a safe low level, causing shock.
- Machine restarts when stop device is reset.
Evidence to record
- Measured value and test point
- Expected value / expected state
- Observed value / observed state
- Pass/fail result and any deviation
- Name/date or responsible person where required
FIELD RULE: A correct stop test proves both how motion stops and what prevents unexpected restart.
PART V
Machine Safety Functions
Machine Safety Functions
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Adapted from Machine Commissioning for Maintenance and Automation Technicians, by Dovydas Kersys. © 2026 Dovydas Kersys. Featured cover image is an AI-generated editorial illustration.