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Check B-axis movement manually

With machine powered off and E-stop engaged, manually rotate the B-axis to feel for binding, rough spots, or excessive resistance in the rotation.

Ensure machine is powered off and locked out before manual manipulation

Inspect B-axis for debris and damage

Check rotary table bearings, chuck mounting, and rotation mechanism for chips, coolant buildup, or damaged components that could cause binding.

Look for witness marks or scoring on the rotary table that indicate contact or binding

Verify workpiece and fixture weight

Ensure workpiece and fixture are within the B-axis weight capacity and properly balanced to prevent excessive motor loading during rotation.

Check machine specifications for maximum B-axis load capacity and moment ratings

Test B-axis servo performance

Power up machine and jog B-axis at slow feed rates while monitoring servo load in CURRENT COMMANDS > DIAGNOSTICS to identify excessive current draw.

Normal B-axis current should be consistent during rotation - spikes indicate binding points

Inspect servo motor cooling fan

Check B-axis servo motor cooling fan for proper operation, debris blockage, or mechanical failure that would reduce airflow over motor housing.

Fan should run continuously when servo drives are powered - listen for unusual noise or vibration

Clean motor air passages

Remove accumulated chips, coolant residue, and debris from servo motor cooling fins and air intake/exhaust passages using compressed air.

Use appropriate PPE and ensure electrical components are protected during cleaning

Verify ambient temperature conditions

Check that machine environment temperature is within specifications and electrical cabinet ventilation is adequate for proper servo drive cooling.

Servo drives generate significant heat - ensure cabinet fans are working and filters are clean

Monitor motor temperature during operation

Run B-axis through normal motion cycles while checking for excessive heat buildup on motor housing using infrared thermometer or touch test.

Motor should be warm but not too hot to touch - excessive heat indicates cooling problems

Check thermistor resistance values

Disconnect B-axis motor feedback connector and measure thermistor resistance across appropriate pins - should read approximately 1-10K ohms at room temperature.

Thermistor resistance decreases as temperature increases - infinite resistance indicates open circuit

Inspect feedback cable integrity

Examine B-axis motor feedback cable for damage, wear, or loose connections at both motor and drive ends, paying attention to flex points.

Power down machine and lock out before disconnecting feedback cables

Test thermistor circuit continuity

With feedback cable connected, measure continuity from servo drive thermistor input pins to motor thermistor to verify complete circuit path.

Wiggle cables during continuity test to identify intermittent connection problems

Monitor thermistor signal at drive

Use servo drive diagnostics or oscilloscope to monitor thermistor signal stability during B-axis motion to identify intermittent sensor failures.

Erratic or noisy thermistor signals often indicate failing sensors or poor connections

Check servo drive temperature and ventilation

Verify B-axis servo drive cooling fans are operating and heat sinks are clean, check for excessive drive temperature using infrared thermometer.

Servo drives should have adequate airflow - blocked ventilation causes drive and motor overheating

Review B-axis servo parameters

Access SETTING > PARAMETERS and verify B-axis servo tuning parameters (gain, acceleration, current limits) are set to factory specifications.

Incorrect servo parameters can cause instability and excessive current draw

Monitor servo drive current output

Use CURRENT COMMANDS > DIAGNOSTICS to monitor B-axis servo current during motion - excessive or erratic current indicates drive problems.

Compare current readings to other axes - significantly higher current suggests drive or motor issues

Check for servo drive fault history

Review ALARMS > ALARM HISTORY for related servo drive faults or recurring B-axis alarms that might indicate progressive drive failure.

Pattern of increasing alarm frequency often indicates failing drive components

Review B-axis programmed moves

Examine part program for B-axis feed rates, rapid moves, and acceleration demands that may exceed motor thermal capacity during continuous operation.

High-speed continuous B-axis indexing generates more heat than intermittent positioning moves

Check B-axis velocity and acceleration limits

Verify SETTING > PARAMETERS for B-axis maximum velocity and acceleration settings are appropriate for motor thermal rating and application.

Factory settings are conservative - custom applications may need thermal analysis

Test with reduced feed rates

Run problematic program with reduced B-axis feed rates (50-75% of original) to determine if lower speeds prevent thermal alarm.

If reduced speeds eliminate alarm, motor is thermally limited at higher speeds

Implement programmed dwell periods

Add G04 dwell commands in program after intensive B-axis moves to allow motor cooling time between high-demand operations.

Even short dwells (1-2 seconds) can significantly reduce motor temperature buildup