231-8CA0

Access motor table configuration

Navigate to MOD function → Machine Parameters → Motor table and locate the affected axis motor configuration.

Always backup current motor table before making changes using the archive function

Verify STR parameter value

Check the STR (lines per revolution) parameter against the encoder nameplate or documentation. Common values are 1024, 2048, or 4096 lines per revolution.

Incorrect STR values will cause position errors and potential crashes

Update and validate configuration

Enter correct STR value, save motor table, and perform controlled axis movement to verify proper operation.

Use manual pulse generator (MPG) for initial movement verification after parameter changes

Inspect encoder physically

Remove encoder cover and visually inspect glass scale or disk for cracks, contamination, or physical damage to reference track.

Power down axis drive before encoder inspection to prevent electrical hazards

Check reference signal quality

Use TNC diagnostic screen (MOD → Diagnosis → Encoder signals) to monitor reference pulse amplitude and consistency during slow manual movement.

Reference signals should show clean square waves with consistent amplitude

Clean or replace encoder

Clean encoder surfaces with appropriate solvent or replace encoder assembly if damage is confirmed. Recalibrate reference point after replacement.

Always use lint-free cloths and encoder-safe cleaning solutions

Perform cable continuity test

Power down system and use multimeter to check continuity of all encoder cable conductors from encoder connector to TNC input module.

Ensure complete power isolation before cable testing to prevent damage to TNC inputs

Check cable routing and strain relief

Inspect cable routing for sharp bends, pinch points, or inadequate strain relief that could cause intermittent faults during axis movement.

Encoder cables should have minimum bend radius of 10x cable diameter

Test signal integrity under movement

With proper connections verified, monitor encoder signals on TNC diagnostic screen while moving axis through full travel to identify intermittent faults.

Intermittent cable faults often appear at specific axis positions or movement directions

Check cable separation and shielding

Verify encoder cables maintain minimum 6-inch separation from power cables and confirm shield connections are proper at both ends.

Shield should be connected to ground at TNC end only to prevent ground loops

Monitor signal quality during operation

Use TNC encoder diagnostic display to observe signal stability during normal machine operation, noting any correlation with spindle or other axis movements.

High noise levels can cause position loss and axis runaway conditions

Implement noise suppression measures

Install ferrite cores on encoder cables, improve grounding, or relocate cables away from noise sources. Consider upgrading to differential encoder signals if available.

Differential encoder signals (A+/A-, B+/B-) provide superior noise immunity compared to single-ended signals

Swap encoder connections for testing

If multiple axes available, temporarily swap encoder connections between working and faulted axis to isolate TNC input module issues.

Ensure axis parameters are also swapped to prevent incorrect scaling during test

Check TNC input module status

Access TNC hardware diagnostics (MOD → Service → Hardware test) to verify encoder input module operational status and error flags.

Document all error codes and module serial numbers for service technician reference

Contact authorized service

If input module failure confirmed, contact HEIDENHAIN authorized service for module replacement and system recalibration.

TNC module replacement requires factory authorization and specialized calibration procedures