SINUMERIK 840D Alarm 3000 Emergency Stop: Troubleshooting Guide

Problem Overview

The SINUMERIK 840D / 840Di / 810D CNC platform raises alarm 3000 Emergency stop whenever the safety chain, drive enable path, or PLC-controlled emergency-stop signal is interrupted. On systems that combine a SIMODRIVE 611D infeed with SIMODRIVE 611D feed/spindle modules, alarm 3000 is frequently accompanied by 300005 At least one module found on the drive bus has not been configured, which indicates the NCK has lost communication with one or more drive modules on the internal drive bus (X101/X102, 12 Mbaud). Operators typically observe that the X / Y / Z axis pilot lamps and the spindle pilot lamp are extinguished, while several diagnostic LEDs on the NCU, the I/R (infeed/regenerative) module, the NE power module, the feed module, and the SIMATIC ET 200M distributed I/O station light up in abnormal combinations. The fault is recoverable but requires a structured diagnostic sequence because alarm 3000 can be triggered from the hardware safety circuit, from the PLC user program, or from NC machine data inconsistencies.

Affected Systems and Components

• SINUMERIK 840D with NCU box (NCU 561.x / 571.x / 572.x / 573.x).
• SINUMERIK 840Di distributed variant with PC-based NCU.
• SINUMERIK 810D with CCU box.
• SIMODRIVE 611D modular drive line-up (I/R module, NE power module, feed modules, spindle module).
• SIMATIC S7-300 / ET 200M PLC sub-rack connected via PROFIBUS-DP or MPI.
• CP 5611 / CP 5613 / CP 5614 communications processor in the programming PG/PC.
• Operator panel (OP 010 / OP 010C / OP 012 / PCU 50).

Alarm Reference

Alarm 3000 - Emergency stop

Alarm 3000 is generated by the NCK when the emergency stop interface signal is cleared. The signal originates in the PLC user program (DB 31, ... DBX 6.0 / DBX 26.0 family of axis-specific interface bits) and is hardware-interlocked with the 24 V emergency-stop chain on terminals 19 / 48 / 63 / 64 / 72 / 73.1 of the NE power module. The alarm is cleared automatically once the emergency-stop chain closes and the drive ready signal (terminal 73.1 with reference to 72) is high again. Operators will see all axis and spindle pilot lamps drop out as long as alarm 3000 is active.

Alarm 300005 - Drive bus configuration mismatch

Alarm 300005 is raised during NCK startup or after a warm restart when the NCK scans the drive bus (X101 / X102) and finds a drive module whose logical slot assignment does not match the configured assignment in machine data MD 13000 DRIVE_IS_ACTIVE[n] or in the drive configuration loaded into the NCK. Typical triggers include: a replaced SIMODRIVE 611D module without re-running the drive commissioning, an unplugged drive bus connector, a defective drive-bus cable, or an NCK battery-backed memory loss after which the original drive assignment was never reloaded.

Hardware Identification and LED Status Map

The first diagnostic step is to read the LED status on every module in the 611D line-up and on the NCU box. Use the table below to interpret the LED pattern observed when alarm 3000 plus 300005 are simultaneously active.

Terminal Voltage Verification

The emergency-stop chain and drive-enable chain are wired between the operator-panel pushbuttons, the external safety relay, and the NE power module terminal block. A multimeter check across the following terminals with reference to terminal 19 (24 V DC reference / 0 V reference) identifies which segment of the chain is open.

Root Cause Analysis

Combining the LED map, the terminal voltages, and the active alarms, the field-typical root causes for a 3000 / 300005 combination on the SINUMERIK 840D / 840Di / 810D are, in order of frequency:

1. PLC user program not loaded or corrupted. The PLC archive (*.arc) loaded into the PLC does not match the commissioned project, leaving axis enable signals in DB 31 / DB 61 cleared. The PF LED on the NCU lights.
2. Drive bus module swap without re-commissioning. A 611D module was replaced (typically a feed module) but the drive configuration in the NCK was not regenerated; the new module reports on X101/X102 but is not in MD 13000 DRIVE_IS_ACTIVE[n]. This is the direct trigger of alarm 300005.
3. Open emergency-stop chain. Safety relay, E-stop pushbutton, or limit-switch contact is open, removing 24 V on terminal 48. Drive modules report drive not ready, axis and spindle pilot lamps extinguish, and alarm 3000 is raised.
4. PROFIBUS / MPI communication loss to ET 200M. The CP 5611 in the PG, the PROFIBUS connector, the terminating resistor, or the PROFIBUS address on the ET 200M is wrong; the BF LED on the NCU and on the ET 200M blink. PLC cannot toggle the enable signals because distributed I/O is offline.
5. NCK machine data inconsistency. After NCK battery replacement or after a series commissioning, machine data such as MD 13000 DRIVE_IS_ACTIVE[n], MD 30130 CTRLOUT_TYPE[n], or the drive telegram assignment no longer matches the connected hardware.
6. Defective drive-bus cable or connector. Even with the correct configuration, a broken shield, kinked cable, or unseated ribbon on X101 / X102 removes one or more modules from the bus scan.

Diagnostic Procedure

Execute the following sequence in the order given; do not skip ahead, because each step isolates a layer of the fault.

Step 1 - Visual LED Survey

1. Power on the cabinet with the main disconnect and the 24 V control supply.
2. Wait for NCU boot completion (PR green, +5V green).
3. Record every LED state on the NCU, I/R module, NE module, every feed module, and on the SIMATIC ET 200M.
4. Compare with the LED map above; identify the first module whose expected LEDs are missing.

Step 2 - Verify External 24 V Distribution

1. Measure 24 V between terminals 19 and 9 (or 19 and 112) at the NE power module.
2. Verify the multi-tap transformer feeding the 24 V power supply; if the tap is mis-selected the 24 V may sag to 22 V or rise to 27-28 V. Both conditions destabilize the I/R module pull-in and the PLC inputs.
3. If the tap is incorrect, change to the correct tap and re-test. A reading of 28 V on 19-63 is a strong indicator of tap mismatch.

Step 3 - Trace the Emergency-Stop Chain

1. Measure 19-48. If 0 V, walk the loop: terminal 48 -> safety relay coil/contact -> E-stop pushbuttons -> limit switches -> terminal 19.
2. Reset the safety relay; many safety relays latch into stop after a power loss and require manual reset.
3. Mechanically depress and release each E-stop pushbutton to verify it returns; verify that no mechanical limit switch is jammed.
4. Re-measure 19-48; expect 24 V DC.

Step 4 - Verify Drive Enable Path

1. Measure 19-63 and 19-64. Both must read 24 V DC for pulse enable to the I/R module.
2. If 19-64 reads 0 V, identify whether it is sourced from a PLC output, the safety relay, or the operator panel. The PLC will only energize this signal if the PLC is in RUN with the correct project loaded.
3. Measure 73.1-72. This is the drive ready output of the I/R module back to the PLC. 0 V confirms the I/R is not ready.

Step 5 - Inspect PROFIBUS / MPI Link

1. Open SIMATIC Manager and select PG/PC Interface -> Properties on the CP 5611 entry.
2. Confirm the interface assignment matches the physical port (MPI or PROFIBUS) and that the baudrate matches the network (12 Mbaud is typical for the SINUMERIK PLC subnet).
3. Select Accessible Nodes; expect the NCU and ET 200M to appear with their configured MPI / PROFIBUS addresses.
4. If the BF LED on the ET 200M is blinking, verify the PROFIBUS address switch on the IM 153 module, the bus connector terminator (ON at both physical ends only), and the integrity of the PROFIBUS cable shield.

Step 6 - Read NCK and PLC Diagnostics

1. From the HMI select Diagnosis -> Alarm -> Clear Log to view the alarm history.
2. From SIMATIC Manager open the PLC online and read the diagnostic buffer of the S7 CPU. Note any OB 100 / OB 102 / OB 122 / SF entries indicating startup or communication faults.
3. Open the NCK machine data list and verify MD 13000 DRIVE_IS_ACTIVE[AX1 ... AXn] = 1 for every axis physically connected.

Step-by-Step Resolution

Resolution Path A - PLC archive reload

1. Obtain the machine-specific PLC archive (*.arc) from the commissioning backup.
2. In SIMATIC Manager select PLC -> Download to station; clear the PLC first if requested (PLC -> Clear/Reset).
3. After download, place the CPU in RUN. Verify the PF LED on the NCU extinguishes.
4. From the HMI confirm the START UP banner disappears and the channel-ready / NC-ready messages appear.

Resolution Path B - Drive bus re-commissioning

1. Place the NCK in a state where the drive configuration can be reloaded: HMI Startup -> Drive commissioning.
2. Run Drive configuration and ensure every drive module is listed; reject the wizard only if the list matches the physical line-up.
3. Save the configuration back to the NCK.
4. For each axis, set MD 13000 DRIVE_IS_ACTIVE[n] = 1 via the HMI Machine Data screen.
5. Perform a warm restart (NCK reset).

Resolution Path C - Emergency-stop chain repair

1. Replace any defective E-stop pushbutton or limit switch discovered in Step 3 above.
2. Reset the safety relay; many types require a manual reset button to be held for 1-3 seconds.
3. Confirm 19-48 = 24 V and 19-64 = 24 V.

Resolution Path D - PROFIBUS repair

1. Replace the PROFIBUS connector on the affected drop; ensure the terminating resistor is ON only at the two physical end nodes.
2. Replace the PROFIBUS cable between the NCU and the ET 200M if the shield is damaged.
3. Verify the CP 5611 is seated firmly in the PG/PC and that the PG/PC interface assignment matches (PROFIBUS 12 Mbaud).

Verification

1. From the HMI confirm alarms 3000 and 300005 are no longer in the active alarm list.
2. Confirm all axis and spindle pilot lamps illuminate green within 5 seconds of NCK ready.
3. Read each axis-specific drive ready bit; verify Drive ready in the HMI axis diagnostics.
4. Issue a controlled axis motion of 1 mm in JOG mode on each axis; verify no alarm reappears.
5. Run the spindle up to a low speed (e.g. 50 rpm) in JOG and verify no 3000 / 300005 reappears.
6. Re-measure 19-48, 19-63, 19-64, and 73.1-72; all should read 24 V DC.

Safety Considerations

Preventive Measures

• Maintain a current backup of the PLC archive (*.arc), the NCK series commissioning archive, and the drive configuration archive. Store copies on a non-volatile server, not just on the programming PG.
• Replace the NCK buffer battery at the manufacturer-recommended interval (typically 4-5 years) to avoid machine data loss.
• Periodically inspect the drive-bus ribbon cables and connectors on X101 / X102 for kinks, oxidation, and proper seating; replace at the first sign of intermittent faults.
• Verify PROFIBUS termination and shielding during each preventive-maintenance visit; use a PROFIBUS tester to measure signal quality.
• Document every hardware swap with the corresponding NCK / PLC archive update so that future recovery is single-step.

Cross-Reference to Siemens Documentation

For commissioning, alarm descriptions, and terminal wiring diagrams, consult the official Siemens manuals:

• SINUMERIK 840D sl / 840Di sl / 840D / 840Di / 810D Fundamentals - functional description of NCK, PLC, drive bus, and commissioning flow.
• SINUMERIK 840D / 840Di / 810D Operator's Guide - HMI operation, alarm list, startup screens.

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