What causes FANUC alarm 066?

Machine system or function indicated by the alarm name has detected a fault. Control parameter or configuration error related to the alarm condition. Hardware component fault on the CNC or machine. Part program error or illegal operation for the indicated function. Machine interlock or safety condition not satisfied.

How do I fix FANUC alarm 066?

1. Note the alarm number and check the Fanuc alarm screen for any sub-code or additional details. 2. Identify the specific machine system or function from the alarm name. 3. Power cycle the machine to clear transient faults. 4. Consult the Fanuc parameter or operator manual for alarm 066 specific remedy. 5. Contact Fanuc service if the alarm persists after basic troubleshooting.

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FANUC Controller

Program/G-code · Intermediate · 15-30 minutes

Alarm 066

Fanuc Alarm 066 - IMPROPER G-CODE IN G71-G73

Alarm 066 occurs when the CNC detects an illegal or incompatible G-code command within the definition block of a multiple repetitive cycle (G71, G72, or G73). These canned cycles have strict restrictions on what commands can be used between the cycle call and its termination, and violations such as additional canned cycles, coordinate system changes, or certain modal commands will trigger this alarm.

FANUCProgram/G-codeIntermediate15-30 minutes

066

Fanuc Alarm 066 - IMPROPER G-CODE IN G71-G73

SYSTEM ALARM 66

Root Cause Summary

Alarm 066 occurs when the CNC detects an illegal or incompatible G-code command within the definition block of a multiple repetitive cycle (G71, G72, or G73). These canned cycles have strict restrictions on what commands can be used between the cycle call and its termination, and violations such as additional canned cycles, coordinate system changes, or certain modal commands will trigger this alarm.

Causes and Fixes

1
Review the program block starting with G71, G72, or G73 and identify the start block (P address) and end block (Q address) sequence numbers that define the roughing path.
2
Examine all blocks between the P and Q sequence numbers for prohibited commands: G70-G76 (nested canned cycles), G50/G92 (coordinate setting), G96/G97 (CSS on/off), G40-G42 (tool nose radius compensation), or M-codes other than M98/M99.
3
Remove or relocate prohibited G-codes outside the canned cycle definition. For coordinate system changes, place G50/G92 before the G71-G73 call. For CSS mode, activate G96 before the cycle begins.
4
Re-execute the program in single block mode (SINGLE BLOCK key on panel) to verify the cycle executes without alarm. Check CURRENT > PROGRAM screen during execution to monitor block-by-block processing.

DIY Feasiblehigh confidence

Call a technician if:

·Parameter corruption suspected
·Repeated alarms after program correction
·Control software issues

Prevention

Always validate G71-G73 profiles contain only G00, G01, G02, G03 movement commands
Set spindle, tool, and coordinate systems before calling roughing cycles
Use program simulation to verify cycle compatibility before running

Common Mistakes

Including drilling cycles within turning roughing profiles
Placing coordinate system changes inside cycle definitions
Adding spindle control commands within the profile geometry

Related Alarms

065 067 010 011

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