231-C420

Access Servo Parameters

Navigate to MOD function → Machine Parameters → CfgAxisServo → Select affected axis to access controller parameters.

Document current values before making changes for rollback capability

Check Current Loop Parameters

Verify MP1420 (Kv factor), MP1421 (Ki factor), and MP1422 (Kd factor) against machine documentation or Heidenhain recommended values for your motor type.

Incorrect values can cause violent machine movement

Perform Servo Optimization

Use TNC servo optimization function via MOD → Machine Parameters → CfgServoOpt to automatically tune controller parameters.

Run optimization with machine unloaded and all axes properly referenced

Validate Stability

Execute slow positioning moves and monitor for oscillation or following errors using the position monitor display.

Start with very slow feedrates and gradually increase

Check Acceleration Feedforward

Verify MP1423 (acceleration feedforward) is within 0-100% range. Values above 80% often cause instability on Heidenhain systems.

Start with 50% and adjust incrementally while monitoring axis response

Verify Friction Parameters

Check MP1430 (static friction) and MP1431 (sliding friction) values match actual machine characteristics and motor specifications.

Excessive friction compensation can cause stick-slip behavior

Test Dynamic Response

Execute programmed moves with varying accelerations while monitoring servo following error in the diagnostic display.

Use TNC's built-in oscilloscope function to visualize servo response

Adjust Parameters Incrementally

Reduce feedforward values by 10-20% increments until stable operation is achieved, then fine-tune upward if needed.

Never exceed manufacturer recommended maximum values

Review Filter Settings

Check MP1440 (notch filter frequency), MP1441 (notch filter depth), and MP1443 (low-pass filter frequency) in CfgAxisServo parameters.

Notch filters should target specific resonant frequencies identified during commissioning

Disable Filters Temporarily

Set MP1440=0 and MP1443=0 to disable filtering, then test axis stability to isolate filter-related issues.

Machine may be noisier but should demonstrate basic stability

Perform Frequency Analysis

Use TNC frequency analysis function to identify actual machine resonances and configure notch filters accordingly.

Multiple notch filters may be needed for complex mechanical systems

Re-enable Filters Gradually

Restore filter settings one at a time, testing stability after each change to identify problematic configurations.

Improper filter frequencies can amplify rather than suppress vibrations

Verify Motor Table Entry

Check MP1400 (motor table number) matches the physically installed motor. Access via MOD → Machine Parameters → CfgAxisServo.

Motor table numbers are typically documented in machine electrical drawings

Validate Motor Parameters

Confirm motor table entries for rated current, voltage, and encoder resolution match motor nameplate and documentation.

Incorrect current limits can damage motor or amplifier

Check Encoder Configuration

Verify encoder type and resolution in motor table matches actual feedback device installed on the axis.

Encoder resolution mismatch is a common cause of this alarm

Update Motor Table if Needed

Create new motor table entry or modify existing entry to match actual hardware configuration, then restart control.

Always backup machine parameters before making motor table changes

Check Amplifier Status

Monitor amplifier diagnostic LEDs and check for additional error codes in the TNC error log that might indicate hardware faults.

Do not operate with suspected amplifier defects - risk of damage

Measure Output Currents

Use TNC current monitor display to observe motor current waveforms for irregularities, spikes, or asymmetry indicating IGBT problems.

Current should be smooth sinusoidal waveforms during constant velocity moves

Perform Amplifier Self-Test

Execute built-in amplifier diagnostics if available, or swap amplifier with known good unit to isolate hardware issues.

Only qualified technicians should handle amplifier replacement

Contact Service Support

If hardware defect is confirmed, document error conditions and contact Heidenhain service for amplifier repair or replacement.

Provide complete error log and parameter backup to service technician