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Common Causes

• Motor encoder (BL motor) producing irregular counts
• Encoder link cable or connector fault on a BL motor
• PG or magnetic encoder fault on a VAC motor
• PG/magnetic encoder cable or connector fault on a VAC motor
• Inverter unit control board fault

Troubleshooting Steps

1. 1Read the code number shown with the alarm: code 1 = Linear axis has exceeded its travel range.; code 2 = Rotary axis exceeded its travel range (360) or limited axis has negative positional data.; code 3 = Limited axis has exceeded its travel range.; code other = Absolute value of encoder value change per position control frequency (1/65536 turn units).
2. 2Read the code: 1 means a linear axis exceeded its travel range, 2 means a rotary axis exceeded 360 degrees or a limited axis has negative positional data, 3 means a limited axis exceeded its travel range; other values are the magnitude of encoder change per control cycle.
3. 3For codes 1-3, jog the axis back inside its travel range and verify the position data and soft limits before retrying.
4. 4Inspect the encoder link cables and connectors on the named axis for damage, oil or loose pins, especially where the cable flexes with axis motion.
5. 5On a BL motor check the motor encoder; on a VAC motor check the PG or magnetic encoder and its cable; substitute known-good parts to isolate the faulty feedback device.
6. 6If feedback hardware is eliminated, have the inverter unit control board checked or exchanged, then re-home the axis and verify normal rapid feedrate without the alarm.