What causes FANUC alarm 316?

The minimum depth of cut (first Q value in G76 second block) is programmed larger than the total thread height (k value). Thread height (k) is entered incorrectly or too small for the thread pitch being cut. Units mismatch where values are entered in inches but machine is in metric mode or vice versa causing scaled values to conflict. Typo or decimal point error in the Q or k parameter resulting in an unrealistic cutting depth ratio. Copy-paste error from a similar program where thread parameters were not updated to match the new thread specification.

How do I fix FANUC alarm 316?

1. Open the G76 cycle block in the program and locate the second line containing the k (thread height) and Q (minimum depth of cut) values, confirm both are present and readable. 2. Verify that the minimum depth of cut Q is less than the thread height k. For example on a 1.5mm pitch thread the height is roughly 0.974mm so Q must be smaller than that value. 3. Cross-check your thread height k against a thread data chart for the specified pitch. The formula for metric threads is k = 0.6495 x pitch, so recalculate and correct if needed. 4. Check that the program units match the active G20 or G21 mode. If the machine is in metric but values were written for inch, scale the k and Q values accordingly. 5. Correct the Q or k value in the program so Q is smaller than k, then restart the program from the beginning of the threading cycle to clear the alarm.

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FANUC Controller

Program/G-code · Basic · 10-20 minutes

Alarm 316

Fanuc Alarm 316 - ILLEGAL CUTTING AMOUNT IN THREAD CUTTING CYCLE

Alarm 316 occurs when the minimum depth of cut (I address) specified in a G76 threading cycle exceeds the total thread height (K address). This causes the CNC to reject the cycle because it cannot execute a single-pass cut larger than the entire thread depth, violating the fundamental logic of the multiple repetitive threading cycle.

FANUCProgram/G-codeBasic10-20 minutes

316

Fanuc Alarm 316 - ILLEGAL CUTTING AMOUNT IN THREAD CUTTING CYCLE

FANUC ALARM 316

Root Cause Summary

Alarm 316 occurs when the minimum depth of cut (I address) specified in a G76 threading cycle exceeds the total thread height (K address). This causes the CNC to reject the cycle because it cannot execute a single-pass cut larger than the entire thread depth, violating the fundamental logic of the multiple repetitive threading cycle.

Causes and Fixes

1
Display the program at the alarm point using MDI/EDIT mode. Locate the G76 block and verify the I and K address values.
2
Check that I address (minimum cutting depth in radius for Type I format or finishing allowance for Type II) is smaller than K address (total thread height in radius). For external threads, typical I values are 0.05-0.2mm.
3
Correct the I value to be less than K value. For example, if K0.8 (0.8mm thread depth), ensure I is programmed as I0.1 or similar smaller value.
4
Reset the alarm using RESET button and execute the corrected G76 block in single block mode to verify proper threading cycle operation.

DIY Feasiblehigh confidence

Call a technician if:

·Parameters 3401-3404 corruption
·Persistent alarm after program corrections
·Suspected servo or encoder issues affecting position feedback

Prevention

Always verify thread calculations before programming G76 cycles
Use thread pitch gauges to confirm specifications
Create standard G76 templates for common thread sizes
Regularly backup and verify threading parameters 3401-3404

Common Mistakes

Confusing thread pitch with lead on multi-start threads
Using diameter values instead of radius in X-axis programming
Forgetting to account for tool nose radius in thread depth calculations
Mixing metric and imperial units in the same program

Related Alarms

315 317 318 320

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