TL;DR
Carriage drive faults on CNC tube benders typically come from servo drive alarms, encoder errors, or lubrication starvation on the carriage linear guides. Check the servo drive alarm code first.
What you might see
- CNC shows carriage axis fault or following error
- carriage moves erratically or not at all
- servo drive fault LED active on the drive cabinet
- grinding noise from the carriage linear guides
Likely causes
Servo drive internal fault from overload, overheat, or bus voltage drop
Encoder feedback cable damaged or connector loose causing position errors
Linear guide rails dry from missed lubrication causing binding and overload
Ball screw contamination with metal chips from the bending process
Required tools
- Servo drive fault code manual
- Grease gun with machine-specified grease
- Multimeter for encoder cable continuity
- LOTO kit
Safety first
- Lock out the machine before manually moving the carriage or inspecting any drive components.
- Never bypass or silence a servo fault without identifying and correcting the underlying cause.
Procedure
- 1
Note the fault code displayed on the servo drive in the electrical cabinet. Look it up in the servo drive manual to identify the specific cause.[1]
- 2
If the fault is an overtemperature alarm, check that the drive cabinet cooling fan is operating and the cabinet filters are not blocked.
- 3
Power down and lock out the machine. Inspect the encoder cable on the carriage servo motor from the motor connector to the servo drive. Check for pinch points or damaged insulation.
- 4
Lubricate the carriage linear guide rails and ball screw with the grease type and quantity specified in the BLM maintenance manual.[1]
- 5
Manually move the carriage along its full travel length with the machine off and feel for any binding or tight spots.
- 6
Power up and perform the CNC homing cycle. Monitor the position feedback on the CNC to confirm the encoder is counting correctly.
- 7
If the fault returns immediately, swap the encoder cable or encoder head as a diagnostic step before replacing the servo drive.
Sources
Schwarze-Robitec BLM Group e-TURN / Smart Tube / Pipe Bender general technical documentation, Schwarze-Robitec
BLM Group e-TURN / Smart tube bender maintenance and electrical documentation, servo axis inspection (general)
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