FANUC SP9078 Alarm 78: Safety Parameter Check Mismatch

FANUC SP9078 means that the spindle amplifier's safety-parameter check result does not match the CNC's safety-parameter check result. The CNC displays SP9078, while the spindle amplifier displays alarm 78. This alarm can occur only when FANUC Dual Check Safety is in use.

SP9078 is a cross-check mismatch between two safety-processing channels. It is not automatically proof that an operator entered an unsafe value. Depending on the applicable FANUC manual and hardware series, the official procedure may begin by setting the approved spindle safety parameters again or may direct replacement of the CNC CPU card and the applicable spindle-amplifier hardware.

For other alarms in this number range, see the FANUC Serial Spindle Alarm Codes SP9034–SP9092.

What Does FANUC SP9078 Mean?

Dual Check Safety uses independent processing to monitor safety-related spindle operation. Both the CNC CPU and spindle CPU check the safety parameters used for the spindle. SP9078 is generated when the results of those checks do not agree.

The alarm therefore identifies a mismatch in the check results, not necessarily a specific parameter that is too high, too low, or outside its permitted range. That distinction is important:

• SP9071 / alarm 71 means the spindle detected a safety-parameter error.

• SP9078 / alarm 78 means the CNC and spindle amplifier did not reach the same result when checking the safety parameters.

The mismatch may require approved parameter data to be set again, or it may indicate a fault in the CNC CPU card or spindle-amplifier electronics. The correct action depends on the CNC, drive series, software, and applicable manual edition.

Which Safety Parameters Are Involved?

For systems covered by the FANUC Series 30i-A Dual Check Safety Operator's Manual B-64004EN/02, the spindle safety parameters identified in the SP9078 procedure are:

These numbers apply to the systems and manual edition that specify them. Other CNC series, software versions, or safety configurations may use different procedures or additional protected data. Always identify the exact manual before entering or restoring any value.

“Set the safety parameter again” means restoring the machine builder's validated values. It does not mean increasing a safety-speed limit until the alarm disappears, copying values from another machine, or guessing a replacement value.

SP9078 Is a Dual Check Safety Cross-Check Alarm

FANUC describes SP9078 as part of the cross-check function. The purpose of the cross-check is to confirm that a safety-related judgment made by one CPU is consistent with the judgment made by another CPU. SP9072, SP9077, and SP9078 identify different spindle-side cross-check results:

• SP9072 compares motor-speed check results.

• SP9077 compares axis-number check results.

• SP9078 compares safety-parameter check results.

On supported controls, the DUAL CHECK diagnosis area includes a spindle-status screen. It can display the cause of a spindle-related cross-check alarm when the CNC safety judgment differs from the other CPU. Record this information before removing power or changing data.

The diagnosis screen helps confirm the alarm category and affected spindle. It does not authorize unplanned changes to protected safety data.

1. Confirm SP9078 and Amplifier Alarm 78

Before changing parameters or replacing hardware, verify:

• The CNC alarm screen shows SP9078 or the corresponding SSPA:78 message.

• The spindle amplifier status display shows 78.

• The machine is equipped and configured with FANUC Dual Check Safety.

• The alarm is assigned to the spindle system rather than a servo or PMC safety channel.

• Any simultaneous CNC, spindle, PW, SV, or DCS alarm is recorded.

If available, open the Dual Check Safety spindle-status diagnosis screen and record the cross-check information. Also record:

• Complete CNC series and model

• CNC CPU card part number and revision

• Complete spindle amplifier or SPM part number, including every suffix

• Amplifier family and hardware revision

• Spindle software series and edition

• A backup or approved record of the current safety parameters

• Whether the CPU card, amplifier, control board, software, or safety data was recently changed

• Whether the alarm appeared at power-up or during operation

These details determine which official procedure applies.

2. Reconcile the FANUC Manual Instructions

The FANUC manuals do not all give the same first action for SP9078:

These instructions are not necessarily contradictory. The Dual Check Safety manual provides a data-restoration action for the applicable control configuration, while the amplifier maintenance manuals identify the hardware locations when the check mismatch remains or hardware is determined to be faulty.

A conservative service sequence is:

1. Identify the exact CNC, amplifier, software, and applicable manual edition.

2. Preserve the existing parameters and compare them with the authorized machine record.

3. If the applicable DCS procedure instructs it, enter the same approved spindle safety values again using the authorized method.

4. Complete the required power cycle or activation procedure from that manual.

5. If SP9078 remains, follow the applicable hardware replacement instruction.

Do not use this general sequence to override a machine-builder procedure written for the specific machine.

3. Restore Only Validated Safety Values

Before re-entering any safety parameter:

• Obtain the machine builder's approved parameter record or a verified backup from the same machine.

• Confirm the CNC series, software, spindle number, and machine configuration.

• Record the current value before making any change.

• Follow the required password, write-protection, and power-cycle procedure.

• Have an authorized person perform the work.

Do not copy parameters from another machine simply because it has the same CNC or spindle amplifier. Machine kinematics, spindle specifications, guarding, safe-speed requirements, and risk assessment may differ.

If there is no verified parameter record, stop and obtain the correct machine data. Guessing a safety value is not an acceptable method of clearing SP9078.

4. Follow the Correct Hardware Procedure if the Alarm Remains

When the approved parameters have been verified or restored and SP9078 remains, use the maintenance manual for the installed amplifier series.

For an αi system covered by B-65285EN/04, the official hardware locations are:

• CNC CPU card

• Spindle amplifier control printed-circuit board

For an αi-B system covered by B-65515EN/01, the official hardware locations are:

• CNC CPU card

• Complete spindle amplifier

FANUC does not state a universal rule that one side must always be replaced first. Use the diagnostic evidence, recent service history, exact hardware family, and controlled substitution with known-good compatible parts to isolate the fault.

The technician sequence of replacing the spindle control board, then the CNC CPU card, and finally the amplifier may be reasonable on a supported αi configuration, but it is not universal. On an αi-B amplifier, complete-unit replacement is the documented drive-side action.

5. Back Up the CNC Before CPU Card Replacement

CNC CPU card replacement can affect system software, option support, parameters, PMC data, offsets, macro variables, and safety configuration. Create and verify the required backups before removing the card.

The backup plan should include, as applicable:

• CNC and spindle parameters

• Protected Dual Check Safety parameters

• PMC ladder and PMC data

• Tool and work offsets

• Macro variables and machine-builder data

• System software and option information

• Existing safety acceptance or check-test records

Do not assume that a normal parameter export contains every protected or machine-builder-specific item. Restoration must follow the procedure for the exact CNC and machine.

6. Select Compatible Replacement Hardware

For the CNC CPU card, verify:

• Full card number and revision

• CNC series and hardware generation

• System software and option compatibility

• Memory and machine-data requirements

• Dual Check Safety support

For the spindle-amplifier board or complete amplifier, verify:

• Full FANUC part number and every suffix

• Amplifier family and hardware specification

• Correct control-board number, when board replacement is supported

• Spindle software compatibility

• CNC, spindle motor, and DCS compatibility

• Connector arrangement and installation requirements

Do not select a replacement by appearance, output rating, base model, or connector count alone. An incompatible component can introduce new software, option, parameter, or safety alarms.

If replacement drive hardware is required, browse FANUC servo, spindle, and power drives or send REACO CNC the complete part number for a compatibility check.

7. Replace the Suspected Hardware Safely

Only qualified personnel should replace a CNC CPU card, spindle-amplifier control board, or complete spindle amplifier.

Before beginning work:

1. Stop the machine using the approved procedure.

2. Isolate and lock out the main power.

3. Wait the specified DC-link discharge time.

4. Verify that the required circuits are de-energized.

5. Use electrostatic-discharge precautions when handling circuit boards.

6. Record board positions, connectors, switches, and removable configuration items.

7. Preserve the original component until repair validation is complete.

Install only verified compatible hardware. Transfer memory, software, option devices, jumpers, or configuration parts only when the applicable FANUC or machine-builder procedure explicitly requires it.

8. Validate the Safety Parameters and Functions

Clearing SP9078 is not sufficient to release the machine for production. FANUC requires the safety parameters and safety functions to be checked after a safety-related component is replaced or safety data is changed.

After parameter restoration or hardware replacement:

• Confirm that SP9078 and amplifier alarm 78 no longer appear.

• Confirm that no new parameter, software, axis-assignment, hardware, or DCS alarm is displayed.

• Compare all applicable safety parameters with the approved machine record.

• Confirm that parameter protection is restored correctly.

• Perform the prescribed Dual Check Safety function check or acceptance test.

• Verify the safe-speed and spindle-stop monitoring behavior required by the machine design.

• Test normal spindle operation only after all safety checks pass.

• Record the restored values, replacement part, test method, and results.

The safety-function test must be carried out by an authorized or qualified person. If safety-function data was modified, the related test must be repeated and documented.

Difference Between SP9071 and SP9078

The two alarms both mention safety parameters but identify different conditions:

Do not assume SP9078 proves that one displayed value is outside its permitted range. The essential condition is disagreement between the two independent checks.

SP9078 Compared With Other Cross-Check Alarms

Always diagnose the exact number shown on the spindle amplifier. Similar wording does not make the repair procedures interchangeable.

For a related internal safety-test alarm, see the FANUC SP9016 Alarm 16 guide.

FANUC SP9078 Diagnostic Table

What Not to Do With SP9078

• Do not bypass or disable Dual Check Safety.

• Do not increase safe-speed values merely to clear the alarm.

• Do not copy safety parameters from another machine without validated equivalence.

• Do not assume SP9078 and SP9071 have identical detection conditions.

• Do not replace hardware before preserving the existing parameters and configuration.

• Do not replace only a control board when the applicable amplifier series requires complete-unit replacement.

• Do not install an unverified CNC CPU card or spindle amplifier.

• Do not return the machine to service before the safety-function check is completed and recorded.

Recommended Troubleshooting Order

1. Confirm SP9078 on the CNC and alarm 78 on the spindle amplifier.

2. Verify that Dual Check Safety is in use.

3. Record all simultaneous alarms and the Dual Check spindle-status diagnosis, when supported.

4. Record the exact CNC, CPU card, spindle amplifier, control-board, and software information.

5. Preserve the current parameters and obtain the approved machine-specific safety record.

6. Identify the exact FANUC and machine-builder procedures for the installed system.

7. If specified, re-enter the approved spindle safety values without altering their validated limits.

8. Complete the prescribed activation or power-cycle procedure and check whether SP9078 clears.

9. If the alarm remains, determine whether the applicable drive-side action is control-board or complete-amplifier replacement.

10. Back up the machine completely before CNC CPU card replacement.

11. Replace the supported fault location using known-good compatible hardware.

12. Verify the restored configuration and all applicable safety parameters.

13. Perform and document the required Dual Check Safety function test before returning the machine to production.

Technical References

• FANUC AC Servo Motor αis/αi Series, AC Spindle Motor αi Series, Servo Amplifier αi Series Maintenance Manual, B-65285EN/04, Alarm Code 78

• FANUC Series 30i-A Dual Check Safety Operator's Manual, B-64004EN/02, Cross Check Function and SP9078

• FANUC Servo Amplifier αi-B Series Maintenance Manual, B-65515EN/01, Alarm Code 78 (SP9078)

Always use the manual edition that applies to the exact CNC, spindle amplifier, spindle software, Dual Check Safety configuration, and machine.

Need Help With FANUC SP9078 Alarm?

REACO CNC provides independent testing, repair, compatibility checking, and replacement support for FANUC CNC CPU cards, spindle-amplifier control boards, and complete spindle amplifiers. Send us the CNC alarm screen, amplifier display, complete CNC model, CPU card number, full spindle amplifier model and suffix, spindle software information, approved safety-parameter record, and details of when the alarm occurs.

Visit the FANUC Technical Support Center for more FANUC alarm guides, or contact REACO CNC for assistance.

Reference Source: Beijing FANUC. This article is based on FANUC technical documentation. The applicable parameter-restoration, hardware-replacement, and safety-validation procedure depends on the exact CNC, spindle amplifier, software, Dual Check Safety configuration, and machine.