Fanuc spindle alarm 22 means current exceeding the amplifier's time rating has flowed — not an instantaneous short like AL-12, but a sustained overload: the amplifier delivered more than its continuous rating for longer than its thermal budget allows. Fanuc names the two causes plainly — high frequency of acceleration/deceleration, and high cutting load — and the official remedy is equally plain: ‘ease the operation conditions.’ The useful work is figuring out why the load crept up, because on a machine that ran this job fine last month, something changed.
First: what does the load meter say?
Watch the spindle load meter through the cycle that trips the alarm:
- Sustained load near/over 100% during cutting → genuine process overload — go to Cause 1.
- Load spikes only during accel/decel, light during cuts → duty-cycle overload — go to Cause 2.
- Load high even at idle or during air cuts → something mechanical or parametric is wrong — go to Cause 3. This is the case ‘ease the conditions’ will never fix.
Cause 1 — High cutting load
- Dull or wrong tooling: the most common reason a long-stable job starts tripping AL-22 — worn inserts can double spindle load at identical parameters. Fresh tooling first, before touching anything else.
- Material change: a harder batch, castings with scale/inclusions.
- Process crept up: raised feeds/speeds, deeper cuts, a new fixture allowing heavier passes — the job simply outgrew the spindle. Reduce depth of cut or feed, or split the operation; if the job genuinely needs more, it needs a bigger machine, not a silenced alarm.
Cause 2 — Accel/decel frequency too high
Every spindle acceleration draws several times continuous current. Programs with frequent speed changes, rigid-tap-heavy cycles, or short bar-work cycles with a stop/start per part can overload the amplifier thermally while every individual cut is light. The same duty-cycle physics as AL-01 and AL-09 — the trio often appears on the same machines. Remedies: combine operations per spindle start, avoid unnecessary M05/M03 pairs, lengthen accel time constants, keep one speed where the process allows it.
Cause 3 — The load is high but shouldn't be
If the load meter is high at idle or in air cuts, ‘easing the conditions’ is treating the symptom. Check:
- Spindle mechanics: failing spindle bearings, an over-tensioned or misaligned belt, a dragging brake — compare idle load % against the machine's historical baseline (another reason to record it when healthy). Hand-rotate the spindle power-off and feel for roughness.
- Chip/coolant packing in the spindle taper or labyrinth.
- Wrong motor parameters after amplifier/board work — over-excitation loads the motor at idle; verify against B-65280EN.
Diagnosis checklist (in order)
- Watch the load meter: where in the cycle does load exceed rating — cuts, accels, or always?
- Cutting → fresh tooling, then review parameters/material; reduce cut if genuinely at the limit.
- Accels → reduce start/stop frequency, lengthen time constants, restructure the program.
- Always/idle → mechanics (bearings, belt, brake), then motor parameters.
- Alarm persists at genuinely light load → have the amplifier's current sensing bench-checked — a drifted sensor can fake an overload.
Related guides
- Fanuc spindle alarm 12 (instantaneous overcurrent)
- Fanuc spindle alarm 01 (motor overheat)
- Fanuc spindle alarm 09 (heat sink overheat)
- Top 5 signs your CNC servo motor needs replacement