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FANUC Controller
Overtravel/Limit · Basic · 5-15 minutes
Fanuc Alarm 109 - FORMAT ERROR IN G08
Fanuc Alarm 109 occurs when the G08 (High-Speed Cycle) command contains an incorrectly formatted P address value. The P value must be either P0 (to disable high-speed cycle) or P1 (to enable high-speed cycle), with no other values or missing P address permitted in the G08 block.
109
Fanuc Alarm 109 - FORMAT ERROR IN G08
Overtravel -X
Axis overtravel -x limit triggered. The machine has reached the software or hardware travel limit in the indicated direction.
Root Cause Summary
Fanuc Alarm 109 occurs when the G08 (High-Speed Cycle) command contains an incorrectly formatted P address value. The P value must be either P0 (to disable high-speed cycle) or P1 (to enable high-speed cycle), with no other values or missing P address permitted in the G08 block.
Safety
- Move away carefully
- Move axis slowly to avoid damaging limit switches or machine components
- Before jogging the axis, ensure that there are no obstructions in the path of travel. A collision could cause damage to the machine or workpiece.
- Be extremely cautious when jogging near the limit switch. Excessive force can damage the switch or the machine.
- Power down the machine before inspecting any electrical components or wiring. Lockout/Tagout procedures should be followed.
- High voltages are present in the machine's electrical cabinet. Only qualified personnel should access the cabinet.
- Moving machine components can cause serious injury. Keep hands and clothing clear of moving parts.
- If the machine continues to overtravel after troubleshooting, contact a qualified service technician.
- Move away from the limit carefully to avoid injury or further equipment damage; ensure emergency stop is accessible before proceeding.
Causes and Fixes
- 1
Press RESET to clear the alarm and place the machine in EDIT mode.
- 2
Navigate to the program containing the error using PRGRM key and search for G08 command at the alarmed sequence number displayed on the alarm screen.
- 3
Examine the P address value after G08. Verify it is either P0 or P1. Correct any values such as P2, P3, or negative values to the appropriate setting.
- 4
Execute a program check run in SINGLE BLOCK mode to verify the G08 command executes without alarm before running production.
Call a technician if:
- ·Hardware limit switches require replacement
- ·Servo encoder failure confirmed
- ·Mechanical binding cannot be cleared
- ·Parameter corruption suspected
Prevention
- Regularly verify work coordinate offsets before program execution
- Include G28 reference return moves in program headers
- Monitor position error trends during preventive maintenance
- Verify software limit parameters match machine mechanical limits
Common Mistakes
- Ignoring work coordinate system selection
- Moving axis manually without checking limit switch status
- Modifying limit parameters without mechanical verification
- Running programs without graphics verification
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