230-0194

Check current velocity settings

Access MOD > Machine Parameters and check MP1020 (maximum velocity) and MP1021 (maximum acceleration) for the affected axis.

Calculate max frequency: Velocity (mm/min) × Encoder lines/rev × Motor revs/mm ÷ 60

Verify encoder resolution settings

Check MP4130 (encoder lines per revolution) and ensure it matches the actual encoder specification to prevent frequency calculation errors.

Incorrect encoder resolution can cause position errors and frequency overruns

Reduce velocity parameters

Temporarily reduce MP1020 by 50% and test axis movement to confirm if frequency limit is the issue.

Modern encoders typically have 1-5 million lines/rev - higher resolutions require lower velocities

Optimize motion parameters

Adjust MP1021 (acceleration) and MP1022 (jerk) to create smoother motion profiles that avoid frequency spikes during rapid changes.

Inspect encoder cable routing

Check that encoder cables are properly separated from power cables and routed through dedicated cable tracks with proper shielding.

Never route encoder cables parallel to motor power cables - maintain minimum 100mm separation

Verify cable shield connections

Ensure encoder cable shields are properly connected at both ends and check continuity with multimeter. Shield resistance should be <1 ohm.

Use TNC diagnostic screen MOD > Diagnosis > Encoder to monitor signal quality in real-time

Check encoder supply voltage

Measure encoder supply voltage at the encoder connector - should be 5V ±0.25V for TTL or per manufacturer spec for other types.

Low supply voltage can cause signal distortion and false frequency readings

Test with encoder disconnected

Temporarily disconnect encoder and check if alarm persists - if alarm clears, issue is encoder/cable related rather than TNC internal.

Monitor encoder signals with oscilloscope

Connect oscilloscope to encoder A/B channels and observe signal quality during slow manual movement - signals should be clean square waves.

Use proper grounding and isolation when connecting test equipment to avoid damage

Check encoder mechanical condition

Manually rotate axis and feel for rough spots, binding, or irregular movement that could indicate encoder bearing damage.

Listen for unusual noises from encoder during movement - grinding or clicking indicates mechanical failure

Verify encoder mounting

Check encoder coupling for wear, looseness, or misalignment. Coupling should have no visible play or damage.

Flexible couplings should show even wear patterns - uneven wear indicates misalignment

Test encoder at different speeds

Use TNC manual mode to test encoder at various speeds from 1% to 50% rapid - note at what speed alarm occurs.

Verify encoder interface type

Check MP4110 (encoder interface) matches actual encoder type: 0=TTL, 1=HTL, 2=EnDat, 3=SSI, etc.

Mismatched interface types can cause 4x frequency multiplication errors

Check encoder evaluation method

Verify MP4120 (encoder evaluation) is set correctly: 0=single, 1=double, 4=quadruple evaluation of encoder signals.

Higher evaluation settings multiply effective frequency - use lowest setting that provides required resolution

Validate encoder input assignment

Confirm MP4100 (encoder input assignment) correctly assigns the encoder to the proper TNC input channel.

Cross-check with electrical drawings to ensure encoder is connected to assigned input

Reset encoder parameters to default

Backup current parameters, then reset encoder-related MPs to default values and reconfigure step by step.

Test with known good encoder

Temporarily connect a verified working encoder from another axis to the problematic input channel to isolate TNC hardware issues.

Ensure encoder types and parameters match before connecting to avoid damage

Check TNC input voltage levels

Measure input voltages at TNC encoder connector - should match encoder output specifications (typically 0-5V for TTL).

Use TNC built-in diagnostics under MOD > Diagnosis > Hardware to check input status

Review TNC error log

Access MOD > Diagnosis > Error Messages and check for related hardware errors or encoder input failures.

Look for patterns of errors that might indicate progressive hardware failure

Contact Heidenhain service

If hardware failure is confirmed, document all test results and contact authorized Heidenhain service for TNC repair or replacement.