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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 the change in encoder value per position control frequency (1/65536 turn units).
2. 2Read the code on the alarm screen: code 1 means a linear axis exceeded its travel range, code 2 a rotary axis exceeded 360 degrees or a limited axis has negative data, code 3 a limited axis exceeded its travel range; any other value is the magnitude of encoder change per control cycle.
3. 3For codes 1-3 check the axis position data and soft limits: jog the axis back inside its travel range and verify the position data is valid before retrying.
4. 4Inspect the encoder link cable and connectors on the named axis for damage, oil or loose pins, especially near moving parts of the machine, and reseat or replace the cable.
5. 5On a BL motor check the motor encoder; on a VAC motor check the PG or magnetic encoder and its cable; substitute with known-good parts to isolate the faulty feedback device.
6. 6If feedback hardware is eliminated, the inverter unit control board is suspect; have it checked or exchanged, then re-home the axis and verify normal rapid feedrate.