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Check Following Error Value

Press CURRENT COMMANDS, navigate to the rotary axis display and observe the following error value during motion. Compare against Parameter 29 setting.

Following error should typically stay under 0.001 inches during normal operation

Inspect Rotary Axis Mechanically

With machine powered down and E-stop engaged, manually rotate the rotary axis to check for binding, excessive friction, or mechanical obstructions.

Ensure machine is fully powered down and locked out before manual inspection

Verify Lubrication and Wear

Check rotary axis bearings, worm gear lubrication, and inspect for excessive wear patterns that could cause binding during rotation.

Look for metal shavings or discoloration in the gear oil which indicates excessive wear

Test Axis Movement

Use JOG mode to move the rotary axis at slow feed rates (10-50 RPM) while monitoring following error in CURRENT COMMANDS display.

Binding will show as periodic spikes in following error at specific rotational positions

Check Encoder Cable Connections

Inspect encoder cable connections at both the motor and drive end. Look for loose connections, corrosion, or damaged pins in the encoder connector.

Power down machine before disconnecting encoder cables to prevent drive damage

Monitor Encoder Signals

Access DIAGNOSTICS > ENCODER and observe the encoder count stability while manually rotating the rotary axis. Look for erratic counting or missing pulses.

Encoder counts should increment smoothly without jumps or reversals during manual rotation

Inspect Encoder for Contamination

Check the encoder disc and optical sensors for coolant, chips, or oil contamination that could interfere with signal generation.

Use compressed air and lint-free cloth with isopropyl alcohol to clean encoder components

Verify Encoder Power Supply

Check encoder power supply voltage at the drive using a multimeter. Should read +5VDC ±5% between encoder power pins.

Low encoder supply voltage often indicates drive problems or excessive cable resistance

Review Servo Parameters

Access SETTING > PARAMETERS and review Parameters 70-79 (servo gains) for the rotary axis. Compare against Haas recommended values for your specific rotary model.

Write down current parameter values before making any changes for easy restoration

Check Velocity and Acceleration Limits

Verify Parameters 17 (Max Velocity) and 18 (Acceleration) are set appropriately for the rotary axis mechanical limits and load conditions.

Reduce acceleration by 25% temporarily to see if following error improves

Perform Servo Optimization

Use the built-in servo optimization routine in DIAGNOSTICS > SERVO OPTIMIZATION to automatically tune the rotary axis parameters.

Ensure rotary axis can move freely through full range before running optimization

Test with Conservative Settings

Temporarily reduce servo gains by 20% and test axis movement to determine if tuning is the root cause of the following error.

If conservative settings eliminate the alarm, gradually increase gains while monitoring following error

Check Drive Status LEDs

Observe the servo drive status LEDs on the rotary axis drive module. Green indicates normal operation, red indicates fault conditions.

Refer to the drive LED pattern chart in the electrical manual for specific fault codes

Monitor Drive Current Output

Use CURRENT COMMANDS display to monitor actual motor current during rotary axis movement. Compare against commanded current values.

Current output should track commanded values smoothly without sudden drops or spikes

Check Drive Temperature

Verify servo drive cooling fans are operating and check for excessive heat buildup in the electrical cabinet that could cause drive thermal protection.

Allow drives to cool before handling and ensure proper ventilation

Swap Drive Module

If available, swap the rotary axis drive with a known good drive module to isolate whether the drive hardware is faulty.

Power down machine and follow proper ESD procedures when handling drive modules

Inspect Motor Coupling

Check the coupling between servo motor and rotary axis for looseness, wear, or damage that could cause backlash or slippage during rotation.

Look for metal shavings around the coupling which indicate wear or misalignment

Check Motor Mounting

Verify servo motor mounting bolts are tight and motor is properly aligned with the rotary axis drive mechanism.

Support motor weight properly when checking mounting bolts to prevent dropping

Test Motor Resistance

With power off, measure motor winding resistance using a multimeter. All three phases should read similar resistance values (typically 1-5 ohms).

Significant resistance differences between phases indicate motor winding problems

Monitor Motor Performance

Observe motor operation for unusual noise, vibration, or heat generation during rotary axis movement that could indicate internal motor problems.

Compare motor temperature after operation with other servo motors - excessive heat indicates problems