Configuring SIMOSIM for SIMOTION D425-2 PN/DP with 4-Axis S120

SIMOTION engineers frequently need a software-only environment to commission, validate, and learn axis control logic before connecting to real SINAMICS S120 hardware. The SIMOTION D425-2 PN/DP controller is a compact, multi-axis motion platform widely used in packaging, converting, and synchronized drive applications. This reference explains the supported simulation paths, the firmware/SCOUT version constraints that determine which simulator you can use, and the step-by-step procedure to build a four-axis synchronized S120 application entirely in software using SIMOSIM, virtual axes, or the SIMIT-based SIMOSIM Advanced behavioral model.

1. SIMOSIM Family Overview

Siemens provides three simulation layers for SIMOTION, each with different hardware coverage and licensing requirements. Choosing the wrong layer is the single most common cause of "SIMOSIM does not start" or "axes do not run" complaints.

Reference: SIMOTION simulation SIMOSIM for SIMOTION SCOUT (ID 109782584); SIMOSIM Advanced (ID 109781536).

2. Compatibility Matrix for D425-2 PN/DP

The D425-2 PN/DP (6AU1425-2AD00-0AA0 / -0CA0 variants) is a dual-interface SIMOTION D with PROFINET and PROFIBUS DP. Firmware version dictates which simulator and which SCOUT version can host the offline image.

3. Prerequisites for SIMOSIM Commissioning of a 4-Axis S120 Application

1. PC platform: Windows 10 (64-bit, build 1607+) or Windows Server 2016/2019, 16 GB RAM minimum (32 GB recommended for SIMIT behavioral model).
2. Engineering software: SIMOTION SCOUT TIA V5.2 SP1 (or V5.3 / V5.4) installed inside TIA Portal V16 / V17 / V18 respectively. Earlier releases such as V4.4 are not supported by SIMOSIM and require the virtual-axis path described in Section 5.
3. Licenses: SCOUT base license, one SIMOTION axis license per simulated axis (4 in this case), and a separate SIMOSIM license per SIMOTION D CPU. SIMOSIM is bundled with SCOUT but the license must be transferred to the local USB license dongle (or Softkey) via the Automation License Manager.
4. Project state: The SIMOTION project must contain the D425-2 PN/DP as the target device, the SINAMICS S120 drive objects for the four axes (S120 CU320-2 DP/PN as drive device), and the technology objects (TO) TO_Servo, TO_Speed, or TO_ExternalEncoder as required.
5. Source-free engineering: Disconnect any real PROFINET cable from the engineering PG. SIMOSIM creates its own virtual PN interface on the loopback adapter.

4. Step-by-Step: Building a 4-Axis S120 Synchronous Application in SIMOSIM (SCOUT V5.1+)

4.1 Create the device pool entry

1. Open TIA Portal and load the project containing the D425-2.
2. Right-click the SIMOTION D425-2 node and choose Properties > Target system. Confirm the firmware version reads V5.x. If it shows V4.4, the project cannot use SIMOSIM - jump to Section 5.
3. Open SCOUT from the TIA Portal context menu via Open in SCOUT TIA.

4.2 Configure the four S120 axes as the real target

Even though SIMOSIM will not actually run the SINAMICS S120 closed loop, the S120 topology must be configured correctly so the project can later be downloaded to real hardware without rework. Insert:

• 1 × SINAMICS S120 CU320-2 PN (6SL3040-1MA01-0AA0) drive device.
• 4 × Active Line Module (ALM) plus 4 × Motor Module (for example 6SL3120-1TE23-0AA4) each connected to one synchronous servomotor such as 1FK7 or 1FT7.
• 1 × DRIVE-CLiQ wiring: CU320-2 → ALM → MM1...MM4 → motors.

The four Motor Modules must be assigned DO numbers 1, 2, 3, 4 in DO-list order. These DO numbers must match the driveAssignment parameter of the SIMOTION technology objects (TO) on the SCOUT side.

4.3 Create the SIMOTION technology objects

In SCOUT open the Axis > Insert technology object dialog and create four instances of TO_Servo:

• Axis1 (leading axis, position-controlled)
• Axis2 (electronic gearing, ratio 1:1 with Axis1)
• Axis3 (electronic camming, cam disk Cam3)
• Axis4 (synchronous torque / speed follower, used for tensioning)

For each axis, set:

• TypeOfAxis.AxisType = REAL
• DriveAssignment.UsedDrive = DO[n]
• SensorConfiguration.Encoder = 1 (motor encoder)

Assign the four axes to a single TO_Gearbox / TO_Cam structure for the synchronized motion program. The standard application pattern for a synchronized four-axis web line is shown in the table below.

4.4 Switch the target to SIMOSIM

1. Right-click the SIMOTION D425-2 in the project tree and select Target system > SIMOSIM.
2. Confirm that the SIMOSIM option is now checked; the icon next to the device will show a small simulation indicator (an outlined cube) instead of the solid target hardware icon.
3. Build the project (Project > Compile and check consistency). The compile must complete with no errors. Common errors are missing axis licenses (E:0080xxx license issue) or DO mismatches (E:0700150 axis configuration invalid).

4.5 Download to SIMOSIM

1. Select the D425-2 node and click Download to target system. The download goes to the local SIMOSIM runtime, not to any external device.
2. Click Copy RAM to ROM if you want SIMOSIM to retain state across restarts of SCOUT.
3. Open the axis control panel (Commissioning > Axis control panel), tick Enable, and click Set. SIMOSIM immediately begins to calculate axis state variables, including simulated following error, encoder counter, and motor temperature. The drive side, however, remains passive - SINAMICS alarms such as F30002 (DC link overvoltage) or F07900 (motor blocked) are not generated by SIMOSIM because the S120 hardware is not modeled.

4.6 Run the synchronized motion program

The MCC chart below (encoded as ST-equivalent) is the minimum program to make the four axes run synchronized under SIMOSIM.

// MCC chart: "Run4AxisSync"
// Program section 1 - initialize
Axis1._enableAxis();                          // enable axis 1, position-controlled
Axis2._enableAxis();                          // enable axis 2
Axis3._enableAxis();                          // enable axis 3
Axis4._enableAxis();                          // enable axis 4
Axis1._setAxisMode(velocity, 60.0, 200.0);    // 60 rpm, acc 200 rpm/s
// Program section 2 - synchronization
Axis2._setGearingMode(1.0, 0.0);              // gearing ratio 1.0 with Axis1
Axis3._setCammingMode(Cam3, Axis1, 1.0, 0.0); // cam to Axis1
Axis4._setSynchronousTorqueMode(Axis1, 0.05); // tensioning torque 5%
// Program section 3 - motion
Axis1._move(360.0);                           // move 360 degrees
// Program section 4 - wait and stop
WAITFOR Axis1._stateOfAxis = AXIS_STANDINGSTILL;
Axis2._disableAxis();
Axis3._disableAxis();
Axis4._disableAxis();
Axis1._disableAxis();

With SIMOSIM the four axes execute the chart with deterministic timing matching the configured IPO cycle (default 4 ms, set in Project > Properties > SIMOTION > Execution system). To inspect the virtual mechanical response, use the SIMOTION trace (Tools > Trace); you can record Axis1 setpoint position, Axis2 actual position, and Axis3 follow-on offset simultaneously.

5. Alternative: Virtual-Axis Path for SCOUT V4.4

If the active project must remain on SIMOTION firmware V4.4 / SCOUT TIA V4.4.0.11 (for example because the target D425-2 hardware has not been flashed to V5.1), the integrated SIMOSIM target will not be available. The supported simulation path is to declare the axes as virtual.

5.1 Convert real axes to virtual

1. In SCOUT open the axis configuration for Axis1..Axis4.
2. In Mechanics > Type of axis set AxisType = VIRTUAL.
3. Delete or disable the DriveAssignment.UsedDrive link - virtual axes have no DO on SINAMICS.
4. Set encoder usage to none or to simulation encoder; this is the only encoder a virtual axis requires.

5.2 Limitations of the virtual axis

• No current/torque loop; the axis state variable _torque is computed from a simple J = 0 model.
• No SINAMICS fault generation; you must program your own fault simulation if you want to test alarm handling.
• PROFINET/PROFIBUS is not exercised - the D425-2's PROFINET interface is not running.
• Positioning accuracy is limited by the simulation encoder step, configurable in axis configuration under Encoder simulation > increments per revolution (default 4096).

Despite those limits, virtual axes are sufficient to teach and validate MCC / ST logic, gear / cam structures, and the HMI interaction.

6. SIMOSIM Advanced (SIMIT behavioral model)

When the project requires realistic S120 response, including drive-side alarms and PROFINET traffic, the proper tool is SIMOSIM Advanced, which pairs SIMOSIM with a behavioral model of the SINAMICS S120 in the SIMIT Simulation Platform. The behavioral model is delivered as a SIMIT library chart (file extension .spn) and is wired to the virtual PROFINET interface of SIMOSIM.

6.1 Component requirements

• SIMIT SP V10 or higher (newer is recommended; see Siemens compatibility matrix in SIMOSIM Advanced (ID 109781536)).
• SIMOTION SCOUT / SCOUT TIA with SIMOSIM licensed.
• SIMOSIM Advanced add-in, which is a separate installer that registers the SIMIT-SIMOTION coupling.
• The behavioral model library matching the firmware of the S120 in the project.

6.2 Architecture

+----------------+    PROFINET loopback   +----------------+   intern   +----------------+
|  SIMOTION D    | <-------------------> |   SIMOSIM      | <--------> |   SIMIT        |
|  (simulated)   |                       |   Advanced     |            |   behavioral   |
|                |                       |   runtime      |            |   model of     |
| TO_Axis1..4    |                       |                |            |   S120 ALM+MM  |
+----------------+                       +----------------+            +----------------+

6.3 Typical fault injection under SIMOSIM Advanced

Because the S120 is now modeled, SIMOSIM Advanced can drive and read the same fault buffer the real drive would expose. The table below maps commonly used test faults to the SIMIT behavioral-model configuration switches.

This is the closest the engineer can get to a real machine before the panel is on the shop floor, and it is the configuration Siemens recommends for new commissioning on D425-2 platforms with V5.2 / V5.3 firmware.

7. Verification Checklist

After every change of firmware version, axis type, or simulator target, run the following verification to confirm the configuration is sane.

1. Project consistency: SCOUT menu Project > Compile and check consistency must complete with green check; address E:0700150 (axis configuration invalid) or E:0000xxx license errors block the SIMOSIM download.
2. SIMOSIM target visible: The device icon in the project tree shows the simulation indicator. If not, the project is still on the physical target - re-check Section 4.4.
3. Download completes: Download to target system should report SIMOSIM runtime: download successful within 30 s for a four-axis project. A download time longer than 2 min usually indicates license or firewall trouble.
4. Axis control panel responds: Set a 90° move on Axis1 and confirm the simulated actual position tracks the setpoint in the axis trace. If the actual stays at 0, the axis is not in Operating enable state - issue _enableAxis from the MCC chart first.
5. Synchronization holds: With Axis1 moving at constant velocity, the trace of Axis2 actual must follow Axis1 actual within ±1 incremental step of the simulation encoder.
6. Fault path: Manually force a torque alarm (_setAxisError on Axis1) and confirm Axis2..Axis4 react via the user-defined alarm handling block.

8. Troubleshooting Matrix

9. Performance & Sizing Notes

For four axes with a 1 ms IPO and 0.25 ms position control cycle, the D425-2 PN/DP CPU load under SIMOSIM stays under 35% on a typical office PC. SIMOSIM does not, however, use the D425-2 hardware at all; it executes on the engineering PG with a software emulator of the SIMOTION runtime. The relevant sizing is therefore the PG's CPU.

• Intel i5 / i7 quad-core, 2.5 GHz or higher recommended.
• Disable Bluetooth and Windows Defender real-time scanning during the trace recording to avoid jitter in the simulated position values.
• Run SIMOSIM and SIMIT in the same Windows process group to keep the inter-process coupling deterministic (Start > Computer Management > Set CPU affinity).

10. Migration Path from V4.4 to V5.1+

For users who started on SCOUT TIA V4.4.0.11 and now need SIMOSIM, the migration procedure is documented in the SCOUT online help under First Steps > Migrating projects. The minimum steps are:

1. Open the V4.4 project in TIA Portal V15.1 with SCOUT V5.1.
2. Accept the device version upgrade prompt and let the tool convert DO and TO references to the V5.1 schema.
3. Recompile and resolve any new warnings - V5.1 introduces stricter type checking on technology objects.
4. Re-validate the axis commissioning panel - position controller defaults (Kp, Tn) were revised between V4.4 and V5.1.
5. Switch the target to SIMOSIM and run the verification checklist of Section 7.

11. Practical Example: Four-Axis Web Synchronization Under SIMOSIM

The following ST snippet extends the MCC chart of Section 4.6 to a typical web-handling application: Axis1 is the unwind, Axis2 is the speed-locked draw, Axis3 is the cutting cylinder with a one-revolution cam, Axis4 is the rewind with tension torque.

// Initialize
IF g_bStart THEN
    Axis1._enableAxis();
    Axis2._enableAxis();
    Axis3._enableAxis();
    Axis4._enableAxis();

    // Master velocity ramp 0 -> 1500 mm/s in 2.0 s
    Axis1._setAxisMode(velocity, 1500.0, 750.0);
    Axis1._setMotionSequence(10, 0.0, 2.0, 1500.0, 0.0);

    // Draw: gearing 1.05 (5% draw)
    Axis2._setGearingMode(1.05, 0.0);

    // Cutting: cam, one rev of Axis3 = 360 deg of product
    Axis3._setCammingMode(CamCut, Axis1, 1.0, 0.0);
    Axis3._setCamParameters(360.0, 0.0, 0.0, 0.0);

    // Rewind: synchronous torque, target 8% motor rated torque
    Axis4._setSynchronousTorqueMode(Axis1, 0.08);
END_IF;

// Continuous trace - capture 4 s at 250 us
g_tTrace.start := TRUE;

Run the chart under SIMOSIM, open the trace viewer, and confirm that Axis2 actual position = 1.05 × Axis1 actual position throughout the ramp, that the cammed cut cycle repeats every 360° of Axis1, and that Axis4 torque settles to the configured 8% within 1.5 s after enable. This is the standard Siemens acceptance test for a four-axis SIMOSIM validation of a web line.

12. FAQ