When a CNC machine performs rigid tapping, the Z-axis linear feedrate must match the spindle's rotary motion precisely to maintain the correct thread pitch. If the spindle lags or the Z-axis overshoots, the threads will strip, or the tap will snap.
: If the positional deviation exceeds the value set in parameter 1829, the CNC system will trigger an "Excess Error (Stop)" alarm.
To view or change this parameter, you must follow the standard Fanuc Parameter Write Enable (PWE) procedure: Parameter toggling while machining - Fanuc - Industry Arena fanuc parameter 1829
Following error at rapid = 800 / 33.3 ≈ 24 mm! But 1829 = 3 mm. Every rapid retraction caused a 24 mm error but the alarm fired at 3 mm – instant fault.
If Parameter 1829 is adjusted too high, the servo loop becomes overly sensitive. The motor will overshoot its target, overcorrect in the opposite direction, and begin oscillating. This hunting behavior prevents the axis from settling, causing an excess error alarm while trying to stop. 3. SV 0438 - Motor Overcurrent / Overload When a CNC machine performs rigid tapping, the
To truly understand Parameter 1829, you must understand (Servo Loop Gain). Parameter 1825, measured in sec⁻¹ or (mm/min)/mm , defines how aggressively the servo corrects errors.
Navigate to the parameter screen on your FANUC control unit: Press the hard key. Press the PARAM soft key. Type 1829 and press NO. SRH (Number Search). Note the value assigned to the problematic axis. To view or change this parameter, you must
If all mechanical and electrical checks pass, consider a modest increase to Parameter 1829. Increase in small increments (e.g., 10–20%) and retest until the alarm clears.
SERVO ALARM: n-TH AXIS-EXCESS ERROR
Modifying core servo parameters should always be approached with care. Keep the following best practices in mind:
Parameter 1829 is axis-specific. For a typical three-axis milling machine, you will see separate values for the X-axis, Y-axis, and Z-axis. Identify which axis is triggering the alarm by noting the alarm message (e.g., "1st AXIS-EXCESS ERROR" indicates the first axis).