Sinumerik 810D Spindle Fault 25201: Reset and Recovery Procedure

Problem Definition

A Sinumerik 810D-controlled milling machine (Hardinge-built, Siemens 810D controller, 480 V three-phase supply) is showing Alarm 25201 "Axis SP drive fault" following a momentary interruption of the 480 V shop supply. The spindle refuses to run up to speed as long as the alarm is active, and a second alarm — 510303 "Mode group not ready / ShopMill E_ASUP not executed [System]" — is displayed before any spindle command is issued. The operator also reports that the machine's Emergency Stop cannot be acknowledged with the reset button, which means the E-Stop interlock chain in the integrated PLC is latched shut and is blocking all axis and spindle enable signals upstream of the NCK.

This fault pattern is typical of the SIMODRIVE 611 digital drive line that the 810D pairs with: a power-loss event places one or more drive modules into a hardware-latched fault state, and that state is held in the drive's I/R (Infeed/Regenerative) and spindle modules until the dedicated reset sequence is performed. The 810D also includes an integrated S7-300-class PLC; if that PLC is not in RUN, or its program references a stale peripheral input image, the E-Stop chain stays engaged even when the NCK is healthy.

Affected Components and Topology

The recovery path depends on which module latched first. On a 480 V 810D system, the typical SIMODRIVE 611 power section is laid out as follows:

The SP (Spindle) drive module in the 810D chain is a SIMODRIVE 611-D 1PM6/1FT6-series module, addressed on the internal drive bus. Alarm 25201 is generated by the NCK when the SP module's "ready-to-operate" contactor drops, when the module pulls its drive-fault line low, or when the I/R module signals a bus or DC-link fault. Because the SP module is the only one whose speed command is being rejected, the fault is almost always localized to that one slot, not the I/R module.

Alarm 25201 — Technical Description

Alarm 25201 is the generic drive-fault message raised by the NCK when one of the assigned drives on the PROFIBUS-equivalent internal drive bus reports an error. The NCK text reads:

25201 Axis %1 drive fault %2

Where %1 is the affected axis name (SP1, SP2, etc.) and %2 is the manufacturer-specific drive error code returned via the drive's status word. The 25201 alarm by itself does not tell you which submodule raised it; it only tells you the NCK lost the ready handshake with the drive. The actual root cause lives in either the SIMODRIVE 611 status word bits or in the 7-segment display on the drive module itself.

Common drives-side causes for 25201 following a 480 V interruption include:

1. DC-link undervoltage during the sag — the drive latched fault code "3" (line supply / DC link) on its 7-segment.
2. Speed-controller encoder feedback loss — the spindle encoder cable or the DRIVE-CLiQ/encoder plug partially unseated during the brown-out, so the drive's regulator drops out with feedback error.
3. Motor over-temperature (PTC) — the spindle motor's thermal contact opened as the drive was decelerating from an uncontrolled state.
4. I/R module "DC link not OK" propagating to all downstream drives — the I/R module itself is healthy but the line-side contactor did not re-engage cleanly.

Cascading Alarms — 510303 and the E-Stop Interlock

Alarm 510303 ("Mode group not ready" / "E_ASUP not executed") is not an independent fault — it is a symptom. ShopMill's E_ASUP (asynchronous subprogram) tries to fire on every mode-group transition; if the mode group is not in the "ready" state, the ASUP is rejected and 510303 is logged. The mode group stays "not ready" because the integrated PLC has dropped the NCK's Mode Group Ready bit, which is held in the NCK/PLC interface DB.

The E-Stop latch is held by the PLC program in DB19 (or customer-named equivalent), bit-driven by:

• DB19.DBX0.0 — E-Stop active (input from the hardware E-Stop chain)
• DB19.DBX0.1 — E-Stop reset request (from the operator panel)
• DB19.DBX0.2 — E-Stop acknowledged (latched output back to the NCK)

Pre-Recovery Safety Checks

1. Verify the 480 V supply is fully restored and stable. Use a DMM or scope on the line side of the UE/UI filter; the sag that caused the fault may still be present.
2. Lock and tag the main disconnect. The SIMODRIVE 611 DC bus stores energy in the I/R module capacitors for several minutes after line power removal — wait at least 5 minutes after powering down before inserting or removing any module.
3. Visually inspect every module in the rack for blown fuses (pop-up indicators on the front of the I/R and drive modules), discolored PCBs, or connector backs that have shifted.
4. Confirm that the spindle motor's encoder cable, power cable, and any PTC/thermal-switch leads are fully seated at both the motor and the drive module.
5. Note the 7-segment display code on the SP drive module before powering the rack back up. This is your baseline.

Diagnostic Procedure

Work the diagnostics from the outside in: NCK alarms → PLC state → Drive bus → Module-level status. Do not clear alarms you have not yet read; the alarm log is your evidence trail.

Step 1 — Read the NCK Alarm History

On the HMI, navigate to Diagnostics → Alarm Log (or the Alarm History soft key on older 810D panels). Capture the full 25201 expansion: the axis identifier (e.g. SP1) and the %2 drive code. Record the timestamp. Cross-reference that code against the SIMODRIVE 611-D drive status word documentation to identify whether the fault originated in the power section (codes 1–7) or the control section (codes 8+).

Step 2 — Check the Integrated PLC State

On the HMI, navigate to Diagnostics → PLC → PLC Status. Confirm the PLC is in RUN, not STOP. If the PLC is in STOP, the E-Stop cannot be acknowledged regardless of the NCK's state.

Step 3 — Inspect the I/R Module

The I/R module's front-panel LEDs indicate the bus state. A healthy post-restoration state is:

Step 4 — Inspect the Spindle Drive Module's 7-Segment

On the SIMODRIVE 611-D SP module, the 7-segment display shows the drive's status code. After a clean 480 V power-up the display should sequence through its boot codes and settle on a steady "0" (run/idle) or "8" (follow-up enable from the NCK). Codes you may see on a faulted SP module include:

PLC Recovery Procedure Using SIMATIC Manager

The 810D's integrated PLC is programmed as a standard S7-300 project. SIMATIC Manager (Step 7 classic, not TIA Portal) is the only supported tool for 810D PLC work.

1. Connect the PG (programming device) to the 810D's MPI/DP port on the operator panel front or the X122 port on the NCU.
2. Launch SIMATIC Manager → File → Open → Project from AS (or open the project backup you previously saved with Save to PG).
3. Set the PG/PC interface to PC Adapter (MPI) at 187.5 kbps (default for 810D), and confirm online visibility with Accessible Nodes (F5).
4. Select the online PLC and choose PLC → Download Station to PG to back up whatever is currently in the PLC. This is your rollback safety net.
5. Compare the online blocks to the offline project. If the online blocks differ (e.g., a partial download was interrupted during the brown-out), proceed to step 6. If they match, go to step 8.
6. Choose PLC → Compile and Download Objects. Download all FB, FC, OB, DB, and SFB/SFC blocks. Do not download the system data (SDB) unless you have a complete hardware backup, as the SDB contains the PROFIBUS and rack configuration.
7. After the download, place the PLC into RUN-P using the PG, or use the operator panel PLC mode selector to switch from STOP to RUN. Confirm the PLC RUN LED is steady green on the HMI.
8. Re-acknowledge the E-Stop. The PLC's E-Stop reset logic in DB19 (or your machine builder's equivalent DB) sets DB19.DBX0.2 on a positive edge of DB19.DBX0.1. Press the physical reset button and monitor DB19.DBX0.2 in the VAT / Monitor/Modify table — if it does not latch, the E-Stop input (DBX0.0) is still high, which means a hardware E-Stop device is still mechanically depressed.

Drive Reset Sequence

After the PLC is RUN and the E-Stop is acknowledged, perform the SIMODRIVE reset sequence:

1. On the HMI, navigate to Diagnostics → Axis Diagnosis → Drive for the SP axis. Confirm the drive status word now shows the drive as "ready" (bit pattern depends on the drive firmware version; typically a status of 0xC031 or 0xC032 indicates ready with no fault).
2. From the HMI alarm line, press the Reset (CANCEL) key to clear alarm 25201. The NCK will send a fault reset command down the drive bus to the SP module.
3. Watch the SP module's 7-segment display. It should drop the fault code and cycle to "0" or "8". If it shows a steady fault code that does not clear, the drive hardware is latched and requires a controlled power cycle.
4. Power-cycle the rack: open the main disconnect, wait 30 seconds for the I/R module precharge resistors to discharge, and re-energize. Observe the full boot sequence of the I/R and SP modules.
5. After the boot, the NCK must re-initialize the drive — this happens automatically on the next NCK Reset / NCK Restart. From the HMI, navigate to Start-up → NCK Reset (password protected, typically SUNRISE or the customer password).

Hardware Substitution — Spindle Drive Control Card

If the SP module's 7-segment stays blank or shows a non-clearing code after the PLC and NCK resets, the discussion's suggestion to replace the spindle drive control card is the correct escalation. The procedure is:

1. Power down the rack and observe the 5-minute capacitor discharge waiting period.
2. Loosen the four front-panel screws on the SP drive module and slide the module partway out of the rack.
3. The control card is a daughterboard mounted on the front of the power section. Release the retaining clips and unplug the ribbon cable to the power section.
4. Install the replacement card — part number depends on the SP module size (e.g., 6SN1118-0DJ11-0AA1 for a 1PM6 18 A spindle module) and must be a Siemens-original or formally re-flashed equivalent.
5. Slide the module back in, re-energize the rack, and repeat the drive reset sequence above. The drive will need to re-learn the motor data and encoder offset; this is normal and is performed by the NCK's drive commissioning routine.

Verification Checklist

Use this checklist before returning the machine to production. Every item must pass.

• ☐ 480 V line supply measured at the disconnect, balanced within ±5% between phases.
• ☐ I/R module RDY LED green, DC link LED on, no red fault LED.
• ☐ SP drive module 7-segment shows steady "0" or "8" — no fault code.
• ☐ PLC in RUN, RUN LED steady green on the HMI.
• ☐ E-Stop button physically released, DB19.DBX0.0 low in monitor table.
• ☐ E-Stop reset pressed, DB19.DBX0.2 latched high in monitor table.
• ☐ NCK alarm 25201 cleared from the HMI alarm line.
• ☐ NCK alarm 510303 cleared from the HMI alarm line.
• ☐ Spindle jog test in JOG mode at 100 RPM, then 1 000 RPM, then 3 000 RPM (or the machine's max RPM) — all without re-raise of 25201.
• ☐ Spindle warm-up program (typically 10 minutes stepped through S1000, S3000, S6000 with no load) completed without alarms.

Related Alarms to Watch

After the recovery, monitor the alarm log for the following companion alarms for at least 24 production hours:

Prevention Recommendations

• Install a 480 V three-phase line monitor with adjustable undervoltage trip (typically set to 90% of nominal, with a 100 ms delay) on the machine's incoming feed. The Hardinge/Siemens combination benefits from a Sag-Immune UPS on the control power — the SIMODRIVE 611's control electronics ride through brief sags, but the 810D NCK can corrupt RAM if the +24 V control rail dips below 18 V.
• Save the PLC project to PG before every maintenance window, and store the backup on a non-volatile medium. The discussion thread's suggestion to "upload the PLC backup using SIMATIC Manager" is exactly the right posture for this kind of fault.
• Document the I/R and SP module 7-segment codes observed at install and after every power-quality event, and keep that log with the machine. This makes the next 480 V interruption a 10-minute fix instead of a multi-day hunt.