Fanuc SP9002 Alarm – SSPA:02 Excessive Speed Deviation

Alarm: SP9002 – SSPA:02 EX DEVIATION SPEED

What Does This Alarm Mean?

The spindle amplifier commanded the spindle to run at a specific speed, but the actual spindle speed could not keep up. The difference between the commanded RPM and actual RPM became too large, so the amplifier generated SP9002 to protect the spindle system.

Simple Meaning: The spindle is trying to reach the requested speed but can’t.

Common Symptoms

SP9002 alarm during spindle start.
Spindle accelerates slowly.
Spindle stops during heavy cutting.
RPM fluctuates.
Machine alarms when changing spindle speed.

Most Common Causes

1. Heavy Cutting Load (Most Common)

The spindle is overloaded and cannot maintain the commanded RPM.

Check:

Deep depth of cut
Large diameter tool
Excessive feed rate
Tool wear

Solution:
Reduce cutting load and optimize machining parameters.

2. Acceleration Time Too Short

If Parameter No. 4082 is set too low, the spindle is forced to accelerate too quickly.

Solution:
Verify and adjust Parameter 4082 according to the machine builder’s recommendations.

⚠️ Never change parameters without backing them up or consulting the machine manufacturer.

3. Mechanical Resistance

The spindle requires more torque because of excessive mechanical friction.

Inspect:

Spindle bearings
Belt tension
Gearbox (if equipped)
Tool holder for jamming

4. Spindle Motor or Amplifier Issue

Possible faults include:

Weak spindle motor
Spindle amplifier output problem
Encoder feedback issue
Loose motor power or feedback cables

Quick Troubleshooting Flow

SP9002 Alarm

Is the machine performing heavy cutting?

Yes → Reduce feed rate and depth of cut.
No → Continue.

Does the spindle reach the commanded RPM without cutting?

No → Check spindle motor, amplifier, and encoder.
Yes → Continue.

Check spindle bearings, belts, and mechanical resistance.

Verify Parameter No. 4082 (Acceleration/Deceleration Time).

Monitor spindle load. If it remains high without cutting, inspect the spindle assembly and amplifier.

Technician’s Tip

If SP9002 occurs only during machining, the problem is usually excessive cutting load or mechanical resistance, not a faulty spindle amplifier. If the alarm appears even with no tool cutting, inspect the spindle motor, encoder, amplifier, and Parameter 4082.

Prevention

Use recommended cutting parameters.
Replace worn cutting tools.
Monitor spindle load regularly.
Inspect spindle bearings and belts during preventive maintenance.
Change Parameter 4082 only after confirming the mechanical system is healthy.