FANUC codes
FANUCOvertravel/LimitIntermediate30-60 minutes

508

Fanuc Alarm 508 - INTERFERENCE: +n

Y+ Overtravel

A tool moving in the positive direction along the n axis has fouled another tool post (two-path control only).

Root Cause Summary

Alarm 508 INTERFERENCE: +n occurs exclusively on two-path (dual-turret or dual-spindle) controlled machines when the control detects potential collision between tool posts moving in the positive direction along the specified axis. This is a software-based interference check that monitors the programmed or commanded positions of both tool posts and triggers when the separation distance violates the safety zone parameters.

Safety

  • Only jog in opposite direction of overtravel
  • Only jog in the opposite direction of the overtravel. Use low jog speed to prevent further damage.
  • Be aware of potential pinch points when jogging the axis. Keep hands and tools clear of moving parts.
  • Power down and lock out the machine before performing any electrical troubleshooting. High voltage is present in the control cabinet and drive system.
  • If the cause of the overtravel is unknown, proceed with caution. The axis may move unexpectedly when power is restored.
  • Consult the machine's safety manual for specific warnings and procedures.
  • Always wear appropriate personal protective equipment and follow machine-specific safety protocols.

Causes and Fixes

  1. 1

    Navigate to SYSTEM > PARAM and check parameters 5470-5479 (interference check enable bits) to verify bit settings for each axis. Confirm parameter 5470 bit 0 (interference check enable) is set to 1.

  2. 2

    Check parameters 5480-5489 (interference area setting for each axis). These define the minimum allowable separation distance between tool posts. Verify values match machine mechanical limits and provide adequate safety margin (typically 50-150mm depending on machine size).

  3. 3

    Review the NC program at the alarm point. Check commanded positions for both paths in CURRENT POSITION screen (POSITION > ACTUAL). Calculate the separation distance along the alarmed axis and compare against parameter 5480+n values.

  4. 4

    If parameters are correct, revise NC program to maintain greater separation during simultaneous operations. Use M-codes for interlock (M68/M69 or custom M-codes) to sequence operations and prevent both turrets from entering interference zones simultaneously.

    Disabling interference check parameters removes critical collision protection. Only adjust after verifying mechanical clearances with manual jogging.

DIY Feasiblehigh confidence

Call a technician if:

  • ·Hardware limit switch replacement needed
  • ·Encoder replacement required
  • ·Dual-path coordination system malfunction
  • ·Parameter corruption requiring factory reset

Prevention

  • Regular limit switch inspection and cleaning
  • Verify program Y-axis limits before running
  • Maintain proper tool post coordination in dual-path programs
  • Periodic encoder cable inspection

Common Mistakes

  • Ignoring software limit warnings before hardware limits trigger
  • Bypassing limit switches instead of fixing root cause
  • Not checking both turret positions in dual-path systems
  • Confusing machine coordinates with workpiece coordinates

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Always verify with your machine manual or a certified technician before performing service procedures.