Pushing NC Files to SINUMERIK 840D sl NCU Local Drive Remotely

1. Problem Definition

On a SINUMERIK 840D sl controller, the standard, documented way to move NC programs, compensation data, or tooling data between an office network and the controller is through the PCU 50 / PCU 70 HMI panel. The PCU hosts a Windows operating system with the SINUMERIK Operate user interface, and Windows file sharing, FTP, and network drive mapping all work against it as they would against any Windows host.

When the 840D sl is configured without a PCU – for example a direct NCU 710 / 720 / 730 / 740 with a thin client or a vendor HMI – the Windows file services disappear with the PCU. The remaining hardware is an NCU running the Siemens Linux-based real-time platform. There is no SMB server, no FTP server, and no Windows share that a remote PC can write to natively. The remote PC user is left with a single HMI softkey labeled Local Drive and no documented procedure to push a file into that drive from outside the controller.

The user's requirement is explicit:

• Transfer must be initiated from the remote PC, not from the machine HMI.
• No mapping of a Windows network drive on the NCU is acceptable.
• The destination is the NCU's local drive (the HMI user memory area exposed in the Local Drive softkey).
• The controller has no PCU; it is a bare NCU installation.

This article compares every documented and field-proven method to satisfy the requirement, with parameters, configuration files, and verification steps.

2. SINUMERIK 840D sl NCU Architecture (No PCU)

The SINUMERIK 840D sl splits the controller into two physical units:

When a PCU is present, the Windows operating system on the PCU owns the file services. The NCU communicates with the PCU over an internal Ethernet link and exposes the PCU's shares through softkeys (Local Drive, Network, USB, etc.). When the PCU is removed, the file services disappear with it, and the Local Drive softkey resolves to internal flash memory on the NCU itself.

That internal flash is the only writable user area the HMI exposes, and it is the only place a remote PC can target. The remote PC cannot reach that flash because the NCU's Linux image does not publish a shareable file service out of the box.

3. Local Drive File System Concepts

The Local Drive softkey in SINUMERIK Operate points to a directory inside the HMI user memory. In a PCU-equipped system, the path is typically:

/user/sinumerik/hmi/data/         (user programs, part programs)
/user/sinumerik/hmi/log/          (logs)
/oem/sinumerik/hmi/data/          (OEM area)
/addon/sinumerik/hmi/data/        (add-on area)
/card/user/                       (CF card user area, when present)

On a PCU-less NCU, the same paths are mapped to internal flash. The remote PC has no direct knowledge of those paths – it can only reach them through whatever service the controller exposes on its Ethernet ports (X120, X127, X130, plus the company network port on the PCU when present).

The HMI's Network softkey supports CIFS/SMB and NFS share mounting, but the direction is always from the NCU to a remote share. The NCU never advertises its own Local Drive to the network unless a service is explicitly added.

4. Why Direct NCU File Push Is Not Native

The NCU's basesys.ini on a stock 840D sl installation shows the protocols that are actually enabled by default on the NCU Ethernet ports:

[SNMP]
SNMPLocation="not specified"
SNMPContact="not specified"
SNMPAutLocation="not specified"
SNMPFunction="not specified"
SNMPStation=""

[DCP]
;InternalDcpEnabled=0
ExternalDcpEnabled=0

[LLDP]
;InternalLldpEnabled=0
ExternalLldpEnabled=0

Only SNMP, DCP (Discovery and Configuration Protocol), and LLDP are exposed. There is no [Samba], no [NFS], and no [FTP] section in the stock image. There is also no sshd daemon running by default on the NCU; the HMI uses a proprietary transfer channel to the PCU, not a stock SSH server.

It is possible to install Samba on a Siemens Linux system, and Siemens has published a procedure for doing so on the SIMATIC IOT2000 (an industrial gateway with a similar Siemens Linux base), but the procedure is not part of the standard 840D sl NCU image and is not supported on a production NCU. The user's research thread on the IOT2000 Samba procedure is linked from Siemens Industry Online Support as a reference only; it must not be assumed to apply to the 840D sl NCU without explicit Siemens approval.

5. Method 1 – Access MyMachine P2P (EES)

Access MyMachine P2P (also referred to as EES – Execute from External Storage in the HMI setup) is the Siemens-supported mechanism for remote PC access to NCU file systems. Two distinct products use the same name family:

• Access MyMachine P2P (TCP/IP direct) – a client/server tool installed on the PCU (or the remote PC) that creates a virtual drive on the remote PC and mirrors NCU Local Drive contents. It uses a Siemens proprietary TCP protocol on a configurable port and does not require a Windows share on the NCU side.
• Access MyMachine P2P (SINUMERIK Integrate) – the server component embedded in SINUMERIK Integrate that hosts the same virtual drive service for plant-wide deployments.

For a PCU-less 840D sl, the relevant question is whether the P2P server is available on the NCU itself. Siemens documentation for Access MyMachine lists the NCU as a supported host platform for P2P server starting with specific SINUMERIK Operate versions; the exact minimum version must be verified against the controller's installed software version (e.g., SINUMERIK Operate V4.x, V5.x, V6.x) before commissioning. Once the P2P server is licensed and active, the remote PC installs the P2P client, configures the NCU's IP address and the shared path that maps to Local Drive, and the file appears as a normal drive letter on the PC. The remote PC can then drag-and-drop NC files into the controller's Local Drive.

This is the closest off-the-shelf equivalent to the Windows shared-folder workflow the user has on PCU-equipped machines.

6. Method 2 – SFTP/SCP via SSH

Several field installations have successfully used WinSCP, the OpenSSH sftp client, or the PuTTY pscp command line against an 840D sl NCU, but only after a non-default modification: the NCU must be configured to run an SSH server. On the Siemens Linux platform, this typically means enabling the dropbear or openssh-server package and starting sshd from an /etc/rc.local hook.

Once the SSH server is running and reachable on the NCU's company-network port (X130 in NCU 730/740, or X120 in NCU 710/720), the remote PC can use:

# Command line (Windows PowerShell with OpenSSH, or pscp)
scp program.mpf [email protected]:/user/sinumerik/hmi/data/

# SFTP session
sftp [email protected]
sftp> cd /user/sinumerik/hmi/data
sftp> put program.mpf
sftp> bye

# WinSCP GUI
Host: 192.168.1.10
Protocol: SFTP
User: manufacturer   (or the NCU user configured in /etc/passwd)
Password: <configured>
Remote directory: /user/sinumerik/hmi/data

The file written to /user/sinumerik/hmi/data/ appears immediately in the HMI's Local Drive softkey because the HMI's local drive is the same directory tree.

The trade-off is supportability: enabling SSH on the NCU's Linux image is a non-standard modification and must be performed with Siemens service involvement so that subsequent SINUMERIK Operate updates, PLC stop/start cycles, or NCK general resets do not overwrite the change. Sites that use this method typically back up the modified image as a system snapshot via the NCU's service menu.

7. Method 3 – Industrial Edge for Machine Tools

Industrial Edge for Machine Tools is the Siemens product line that ships an Edge gateway (the SIMATIC IPC227G-based Edge Box or a virtual Edge) with apps such as the SINUMERIK Integrate Analyze MyCondition and the Edge File Transfer app. The Edge box is the device that publishes the SMB / Samba share to both sides:

• Between the Edge box and the 840D sl NCU, a virtual drive is mounted using the proprietary Siemens protocol, so the NCU sees the Edge as a network drive.
• Between the Edge box and the office network, the Edge box publishes a standard SMB share that remote PCs can use like any other Windows file server.

The drawback is the additional hardware: a SIMATIC IPC227G or equivalent Edge device, a Siemens Industrial Edge license, and the maintenance of the Edge device as a separate asset. For a single machine, the cost-benefit is often negative; for a multi-machine cell, it is competitive with multiple P2P licenses.

8. Method 4 – SINUMERIK Integrate Manage MyPrograms / Manage MyResources

SINUMERIK Integrate is the Siemens product family for plant-wide NC program and resource management. The relevant apps for remote file push are:

The user in the source thread was pointed to SINUMERIK Resource Management for a Siemens-supported workflow. Manage MyPrograms runs on a server in the office network; the controller side is the Integrate Client which receives program files and writes them to the configured NCU directory. Once the integrate client is configured (typically during commissioning of the SINUMERIK Integrate suite), the office user pushes programs through the Manage MyPrograms UI and the controller receives them automatically without an interactive HMI session.

This is the most scale-appropriate answer for shops that have more than a few 840D sl controllers; for a single machine it is heavyweight.

9. Method 5 – Network Drive Mapping (PCU-equipped Reference Only)

On a PCU-equipped 840D sl, the workflow the user already uses is:

1. On the PCU, create a Windows shared folder (e.g., D:\nc_transfer).
2. On the HMI, configure a network drive in the Setup → Network softkey pointing to the PCU share as \<PCU-IP> c_transfer with the appropriate user credentials.
3. From the office PC, copy files into the shared folder on the PCU. The HMI sees them as a network drive; they can be executed, copied, or processed.

This requires a PCU and is explicitly excluded by the requirement. It is included here only as a reference for the procedure, so that the differences in the PCU-less path are visible.

10. basesys.ini Protocol Configuration

The basesys.ini file on the NCU lives in /card/system/etc/ or /oem/system/etc/ depending on where the system integrator keeps customizations. The default protocol block shown in section 4 can be extended with the following settings when commissioning a network-aware NCU:

[SNMP]
SNMPLocation="Cell 3 / Machine 7"
SNMPContact="[email protected]"
SNMPAutLocation="Plant A / Building 4"
SNMPFunction="Milling"

[DCP]
ExternalDcpEnabled=1     ; required for PROFINET device discovery from TIA Portal

[LLDP]
ExternalLldpEnabled=1    ; required for topology discovery in SINEC NMS

[internalHTTPServer]     ; SINUMERIK Operate internal web server (HMI Web)
;EnableWebAccess=1
;Port=8443

None of the standard blocks enable file transfer services – they only enable management and discovery protocols. To enable a file service, one of the methods in sections 5–8 must be deployed, and the integration is documented in the product-specific manual, not in basesys.ini.

11. Method Comparison Matrix

12. Step-by-Step: Enabling SFTP Access on a PCU-less NCU

Use this procedure only after Siemens service approval for a non-standard Linux modification. The procedure is a field example, not a Siemens-published step list.

1. Confirm the controller's software version. Read the SINUMERIK Operate version and the NCU's Linux version from HMI Setup → Version. The SFTP procedure requires an NCU running a Siemens Linux version that supports the package management used in step 4. Older versions (pre-V4.5 SP2) typically do not.
2. Back up the NCU's system card. Insert a USB stick, enter service mode, and use the NCU service menu to write a complete image. The backup is required because later steps modify the Linux userland.
3. Connect a service laptop to X127. X127 is the NCU's service port (192.168.214.1/24). Configure the laptop with a static address in the same subnet, e.g., 192.168.214.10.
4. Open a root shell on the NCU. From the service laptop, open a Siemens service shell session (procedure depends on the controller's service access policy). Confirm uname -a returns a Siemens Linux kernel version.
5. Install and start the SSH server. On Siemens Linux images that ship with opkg package management, the command is opkg install openssh-server. Start the daemon with /etc/init.d/sshd start and verify with netstat -tln | grep :22.
6. Create a non-root service user. Do not enable root login over SSH. Add a user with adduser ncftp, set a strong password, and restrict the user to SFTP-only by setting /usr/libexec/sftp-server as the user's shell in /etc/passwd and adding the Match User ncftp block to /etc/ssh/sshd_config with ForceCommand internal-sftp and ChrootDirectory /user/sinumerik/hmi/data.
7. Open the company network port for SFTP. The NCU's X130 (or X120 on NCU 710/720) faces the company network. Configure the firewall to allow TCP/22 from the office subnet only. Do not expose SSH to the broader plant network without a VPN or jump host.
8. Test from the office PC. Use WinSCP or the OpenSSH client to connect. The first connection prompts to accept the NCU's host key. A successful login shows the remote directory /user/sinumerik/hmi/data, which is the same path as the HMI's Local Drive softkey.
9. Verify the file appears in the HMI. On the HMI, open Program Manager → Local Drive. The transferred file must be visible. If the file extension is .mpf, it is selectable as a part program.

13. Verification and Diagnostics

After commissioning any of the methods above, run the following verification steps:

1. HMI visibility test. Transfer a uniquely named test file (e.g., VERIFY_001.MPF) from the remote PC. Confirm the file appears in HMI Program Manager → Local Drive within five seconds.
2. Bidirectional test. From the HMI, save a program (e.g., a small circular interpolation test) to Local Drive. Confirm the remote PC sees the same file at the source path.
3. NCK executable test. Select the transferred program and execute it in MDI or AUTO mode. Confirm no alarm 14011 (channel %1 block %2 – program %3 not found) or alarm 12080 (channel %1 block %2 – error in NC block) appears. These are the standard alarms for missing or malformed programs.
4. Permission and ownership test. Confirm the transferred file's owner and group match the HMI's expected user (typically operator or hmi). A file owned by root may not be deletable from the HMI.
5. Connection persistence test. Power-cycle the NCU. Confirm the file service restarts automatically (P2P server, Edge app, or sshd) without manual intervention.
6. Network probe. From the remote PC, run Test-NetConnection -Port 22 <NCU-IP> (PowerShell) or nc -vz <NCU-IP> 22 (Linux) to confirm the service port is reachable.

14. Field-Proven Caveats

• Alarms after transfer. If the HMI shows Program not found or Channel not ready after an SFTP transfer, check the file's .mpf extension and the encoding (the NCU expects ISO 8859-1, not UTF-8, in some legacy configurations). WinSCP's default text mode can corrupt non-ASCII characters; force binary mode for NC files.
• Service resets. An NCK general reset or an SINUMERIK Operate software update can reset the SSH configuration to default. The backup image taken in step 2 must be kept current, and the commissioning procedure must be repeated after every controller update.
• Network address conflicts. The NCU's X127 service port is 192.168.214.1/24. If the office network happens to use the same subnet, the laptop or office PC cannot reach the NCU on the service port. Reconfigure the laptop's NIC to an unused address in the same subnet (e.g., 192.168.214.50) or move the commissioning to a dedicated service VLAN.
• HMI refresh lag. The HMI's file list is refreshed on entry to Program Manager and on a periodic timer. If a file pushed via SFTP does not appear immediately, leave Program Manager and re-enter it, or press the refresh softkey.
• Cybersecurity hardening. Exposing any service on the NCU to the office network must follow IEC 62443 zone-and-conduit principles. A 840D sl NCU on a flat office network with no firewall is a security incident waiting to happen.

15. FAQ