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Common Causes

• Mechanical binding or excessive friction in the axis due to crashed tooling, impacted way covers, or insufficient lubrication on ball screws and ways
• Servo motor cable damaged with shorted phases or degraded insulation causing current spikes and ground faults
• Servo amplifier tuning parameters set incorrectly causing oscillation, hunting, or constant high current draw to maintain position
• Failed servo motor with shorted windings, bad encoder, or seized bearings creating excessive load on the drive
• Loose or corroded connections at the servo motor encoder or power cable creating intermittent high resistance and current surges

Troubleshooting Steps

1. 1Step 1: Note which axis faulted from the alarm message and manually rotate the ball screw by hand in MDI mode with servo power off to check for unusual resistance or binding
2. 2Step 2: Access Diagnostics page and check current draw on the faulted axis at rest and during slow jog - compare to other axes (typically under 2 amps at rest)
3. 3Step 3: Inspect the servo motor cable from motor to amplifier for damage, verify all connections are tight at motor, amp, and junction boxes with no corrosion or burn marks
4. 4Step 4: Check way lubrication system operation and manually lubricate the affected axis ways and ball screw if auto lube is not functioning properly
5. 5Step 5: Verify servo motor encoder feedback by observing position counts in Diagnostics while jogging - erratic counts indicate encoder cable or motor encoder failure
6. 6Step 6: Swap servo amplifier with a known good axis to determine if fault follows the amp (bad drive) or stays with axis (motor or mechanical issue), then replace failed component