231-4210

Access PLC Program Source

Navigate to MOD > PLC > Edit Program to view the PLC source code. Look for axis enable outputs typically named similar to M4000-M4007 for X-C axes or outputs like O32-O39 depending on PLC program structure.

Common Heidenhain PLC programs use markers M4000+axis_number for drive enable. X=M4000, Y=M4001, Z=M4002, etc.

Verify Enable Logic Conditions

Examine the PLC logic that sets the enable marker for the affected axis. Confirm conditions like E-STOP released (typically M8000), controller ready (M8010), and no active alarms are all satisfied before drive enable is set.

Use PLC Debug mode to watch marker states in real-time while cycling power or E-STOP to see which condition fails.

Check Physical Output Assignment

In MOD > PLC > I/O Assignment, verify that the PLC output marker is correctly mapped to the physical output terminal connected to the drive enable input. Confirm terminal number matches wiring documentation.

Do not modify I/O assignments without complete wiring documentation - incorrect changes can cause unexpected machine motion.

Force Output for Testing

In PLC Debug mode, use the Force function to manually set the drive enable marker to TRUE (1). Observe if drive becomes ready. If successful, the PLC logic conditions are the problem, not the hardware.

Only force outputs with machine in safe state and all personnel clear. Remove force conditions immediately after testing.

Locate Drive Enable Terminals

Identify the enable input terminals on the drive amplifier for the affected axis - typically labeled STO, STO_A/STO_B, or ENABLE. Consult amplifier documentation for exact terminal designations.

Most Heidenhain-compatible drives use dual-channel STO inputs requiring both channels bridged with 24VDC for enable.

Measure Enable Circuit Voltage

With controller powered and E-STOP released, measure DC voltage between enable terminals and 0VDC common. Should read approximately 24VDC. If 0V, trace circuit back through safety relays, E-STOP chain, and interlock switches.

Use only CAT III rated multimeter. Do not bypass safety circuits for testing purposes.

Check Safety Relay Outputs

Locate the safety relay module (typically Pilz, Schmersal, or similar) in control cabinet. Verify output contacts are closed using continuity test or LED status indicators. Reset safety relay if required per manufacturer procedure.

Many machines use dual-channel safety relays requiring manual reset after E-STOP - look for a reset button on the relay module itself.

Verify Wiring Continuity

With power OFF, perform continuity test from PLC output terminal through all intermediate connections to drive enable input terminal. Check for loose terminals, broken wires, or corroded connections in the enable circuit path.

Disconnect power and lock out before continuity testing. Re-verify wiring against schematic before re-energizing.

Check Amplifier Status Indicators

Examine LED indicators on the drive amplifier module for the affected axis. Red or flashing LEDs typically indicate fault states. Note the LED pattern and reference amplifier manual for specific fault code.

Common Heidenhain-compatible drives (AEXU/UMC series) use 7-segment displays or multi-color LEDs - record exact pattern before attempting reset.

Access Drive Diagnostics via HSC

If using Heidenhain UM or EB modules with HSC (Heidenhain Serial Communication), connect to System Parameters > HSC > Drive Diagnostics to read internal drive status and fault registers. Record all active fault codes.

Navigate MOD > Settings > Components to access individual drive modules if configured in the control.