230-0005

Visual inspection of all E-STOP buttons

Check all emergency stop buttons on machine, pendant, and control cabinet. Look for pressed, stuck, or damaged mushroom buttons.

Do not bypass safety circuits - always repair properly

Release and twist E-STOP buttons

Pull and twist each E-STOP button clockwise to release. Verify mechanical action is smooth and contacts engage properly.

Listen for audible click when button releases - indicates good contact action

Check PLC diagnostics in TNC

Access MOD function, select PLC, then INPUT/OUTPUT to monitor E-STOP input status (typically X121.1). Verify signal goes high when all buttons released.

Use TNC's PLC monitor to trace signal path through safety relay logic

Reset alarm sequence

Press CE key to clear alarm, then NC START to reinitialize control-ready sequence after confirming all E-STOPs are released.

Check safety relay status LEDs

Locate safety relay module in electrical cabinet. Verify power LED is on and output LEDs indicate proper relay state.

Only qualified electricians should work inside electrical cabinets with power on

Verify 24VDC supply to safety circuit

Measure 24VDC at safety relay input terminals. Check fuses F1/F2 for 24V supply circuit feeding safety relays.

Use TNC parameter 128200 SUPPLY_VOLTAGE to monitor system voltages

Test safety relay reset function

With all E-STOPs released, press safety relay reset button. Monitor PLC input X121.1 in TNC diagnostics for proper signal transition.

Some safety relays require specific reset sequence - check relay documentation

Check wiring continuity

With power off, verify continuity through E-STOP chain from safety relay output back to PLC input terminal.

Check PLC program status

Access TNC MOD function, select PLC, then STATUS. Verify PLC program is running and no PLC errors are present.

Look for PLC STOP condition or syntax errors in program

Monitor control-ready marker

In PLC diagnostics, check marker M7 (typical control-ready marker). Trace logic conditions preventing M7 from being set.

Use TNC's PLC editor to single-step through safety logic sequence

Verify safety interlock inputs

Check all safety door switches, light curtains, and guard switches that feed into control-ready logic. Monitor respective PLC inputs.

Never defeat safety interlocks - repair faulty switches properly

Compare with backup PLC program

If available, compare current PLC program with known good backup using TNC's PLC compare function to identify unauthorized changes.

Check TNC system parameters

Verify parameter 128100 EMERGENCY_STOP_INPUT is set to correct PLC input address. Check parameter 128101 for proper safety configuration.

Use parameter backup/restore function to compare with known good configuration

Perform TNC system diagnostics

Access MOD function, select SYSTEM INFO, then DIAGNOSTICS. Check for hardware errors on PLC interface modules.

Document all error codes before attempting any system resets

Restart TNC control system

Perform controlled shutdown via MOD function, then power cycle TNC. Monitor startup sequence for proper PLC initialization.

Allow full 2-minute initialization before testing E-STOP circuit

Test PLC I/O functionality

Use TNC's I/O test function to manually toggle outputs and verify PLC interface card communication is working properly.

Inspect E-STOP circuit wiring

Visually inspect all wiring in E-STOP chain for damage, loose connections, or corrosion. Pay attention to flex cable areas and terminal blocks.

Turn off power before inspecting connections in electrical cabinet

Check terminal tightness

Verify all terminals in E-STOP circuit are properly tightened. Check PLC input terminal X121.1 and safety relay connections.

Use proper torque specifications for terminal blocks - typically 0.5-0.8 Nm for small terminals

Test circuit continuity

With power off, use multimeter to verify continuity through entire E-STOP circuit from 24V supply through all switches back to PLC input.

Actuate each E-STOP button while testing to verify proper contact operation

Check for voltage drops

With circuit powered, measure voltage at each connection point to identify high resistance connections or voltage drops exceeding 0.5V.