Lockout Tagout

Lockout/Tagout (LOTO) is a formal hazardous energy control procedure used to shut down, isolate, secure, and verify CNC machines before servicing. It prevents unexpected startup or release of stored energy by physically locking energy-isolating devices and applying tags to identify the authorized worker responsible.

In a typical CNC cell, an operator or maintenance tech first executes the machine's normal stop procedure to park axes, decelerate the spindle, and engage servo brakes. Then, they open the main disconnect, isolate air supply and hydraulic valves, and lock out auxiliary systems like coolant or lubrication pumps—each with a personal lock on the appropriate energy-isolating point or a group lockout hasp for multiple workers. Stored energy is released or restrained: hydraulic and pneumatic pressure bled to zero, moving parts allowed to stop completely, and gravity-loaded components blocked or supported. Verification is critical—the worker attempts a normal start and checks gauges for zero pressure or motion. In millwork assembly or edgebanding, the same logic applies to pinch-point systems, feed rollers, knife stations, clamp frames, and conveyor sections where residual air pressure or spring tension can still cycle hardware after power removal. The goal is to keep the machine 'off and still' during non-routine servicing.

• ⚠️Skipping residual-energy release: A CNC with locked electrical power still has trapped pneumatic pressure in a clamp circuit, causing a vise or actuator to move during service and crush fingers.
• ⚠️Failing to isolate all sources: The main power is locked out, but an auxiliary circuit like hydraulic pump or vacuum supply remains active, allowing unexpected motion or axis drift during maintenance.
• ⚠️No verification step: Workers trust the disconnect without attempting a start or checking gauges, so a mislabeled disconnect or stored mechanical energy goes unnoticed until a technician enters the danger zone.