330-0039

Access Machine Parameter Display

Navigate to MOD > Machine Parameters > Input Signals to monitor permissive key input status in real-time.

Use PLC program status display to see actual input states

Test Key Switch Continuity

With machine power off, use multimeter to check continuity across permissive key switch contacts in both positions.

Ensure LOTO procedures before electrical testing

Verify Signal at TNC Input

Check voltage at TNC input terminal while operating permissive key - should show 24VDC when activated.

Check machine parameter MP7500.x for permissive input assignment

Replace Defective Switch

Install new permissive key switch ensuring proper wiring connections and test axis movement permission.

Verify switch ratings match original specifications

Check PLC Program Logic

Access PLC program via MOD > PLC > Program and verify permissive key input logic in the safety interlock section.

Look for M01 markers related to permissive functions

Verify Machine Parameter MP7500

Check MP7500.x series parameters for correct permissive input assignment and polarity settings.

Document original parameter values before making changes

Test PLC Input Mapping

Use PLC status display to confirm permissive key input is properly mapped and responding to physical switch activation.

Cross-reference with electrical drawings for correct input assignment

Correct PLC Configuration

Modify PLC logic or machine parameters as needed and perform complete axis test cycle to verify proper operation.

Test all safety interlocks after PLC modifications

Trace Permissive Signal Path

Follow wiring from permissive key switch to TNC input terminal using electrical schematic diagrams.

Check for wire damage at cable flex points and connectors

Test Circuit Continuity

Perform end-to-end continuity test from switch terminals to TNC input with power disconnected.

Disconnect power and verify zero energy state before testing

Inspect Connection Points

Check all terminal blocks, connectors, and junction boxes in the permissive signal path for loose or corroded connections.

Use thermal imaging to identify high-resistance connections

Repair Wiring Faults

Replace damaged cables or repair connections, then verify proper signal transmission during axis testing.

Use proper wire gauge and insulation ratings for replacement

Identify Input Module Location

Locate the specific TNC input module handling permissive signals using machine parameter MP7500.x assignments.

Check TNC hardware configuration documentation

Test Input Module Function

Apply known good 24VDC signal to input terminal and verify recognition in TNC input status display.

Ensure correct voltage levels to prevent module damage

Check Module LED Indicators

Observe input module LED status while activating permissive key - LED should illuminate when signal is present.

Compare with adjacent working inputs for reference

Replace Input Module

Install replacement TNC input module and reconfigure machine parameters if necessary to restore permissive function.

Power down TNC completely before module replacement

Review Safety System Architecture

Examine complete safety circuit including E-stops, guards, and permissive interlocks for proper series/parallel configuration.

Check for safety relay coil feedback loops

Test Safety Circuit Isolation

Temporarily isolate permissive circuit from other safety devices to verify independent operation.

Maintain all other safety protections during testing

Verify Safety Relay Operation

Check safety relay contacts and coil operation in the permissive circuit using multimeter and relay status indicators.

Look for welded contacts or coil resistance issues

Reconfigure Safety Integration

Correct safety circuit wiring or logic to ensure proper permissive signal transmission to TNC control.

Validate all safety functions after circuit modifications