231-C280

Verify Motor Pole Pairs

Check the motor nameplate or documentation for the correct number of pole pairs. This is typically 3-5 for standard servo motors. Pole pairs = number of poles / 2.

Common Heidenhain motor configurations: standard servo motors typically have 3-4 pole pairs, while torque motors may have 10-20 pole pairs.

Access Machine Parameter MP1810

Enter MOD mode, navigate to Machine Parameters, select the affected axis, and locate MP1810 (motor pole pairs). Compare the configured value with the motor specification.

Changing MP1810 requires machine manufacturer authorization and will affect motor commutation for all operations.

Correct and Test

If MP1810 is incorrect, enter the correct pole pair value, save parameters, perform a control restart, and re-execute the encoder commutation routine for this axis.

After changing MP1810, always run the automatic commutation procedure rather than manually setting MP1800.

Check Commutation Offset Value

Access MP1800 for the affected axis via MOD > Machine Parameters. A value of 0 or -1 typically indicates commutation has not been performed or the value was lost.

Document MP1800 values for all axes before any encoder replacement - this can save significant setup time.

Execute Automatic Commutation

Navigate to MOD > Test > Encoder Commutation (exact path varies by TNC version). Select the affected axis and initiate automatic commutation. The motor will rotate slowly to determine the correct offset.

Ensure the axis can move freely approximately 1-2 motor revolutions without collision. Remove any workpiece and retract from machine limits.

Verify and Save

After commutation completes, verify MP1800 now contains a value between 0-359 degrees. Save machine parameters and perform a test movement in manual mode to confirm smooth operation.

A properly commutated axis will show minimal current ripple and run smoothly at low speeds - check in diagnosis display during slow jog.

Inspect Encoder Physical Mounting

Power down the machine and manually check the encoder rotor coupling to the motor shaft. Verify the encoder rotor set screw or coupling is tight and properly seated.

Disconnect power and verify lockout/tagout procedures before accessing motor/encoder components.

Check Encoder Stator Alignment

Verify the encoder stator housing is firmly mounted to the motor with correct airgap (typically 0.15-0.3mm for Heidenhain encoders). Check for any physical damage or debris in the airgap.

Use a feeler gauge to verify encoder airgap uniformly around the rotor - uneven gap indicates misalignment.

Verify Shaft Coupling Integrity

Inspect the mechanical coupling between encoder and motor shaft for wear, slippage marks, or damage. Ensure proper torque on all mounting hardware per encoder specifications.

Look for witness marks on the shaft and encoder rotor - these indicate slippage has occurred and commutation is invalid.

Re-establish Commutation

After correcting any mechanical issues, perform the encoder commutation procedure again to establish a new valid MP1800 value based on the corrected mechanical alignment.

Perform commutation twice and compare MP1800 results - they should be within 2-3 degrees if mechanical mounting is solid.