SINUMERIK PCU50.3 File Storage: Recovering Deleted NC Programs

1. SINUMERIK 840D sl Storage Architecture Overview

The SINUMERIK 840D sl control separates operator-side mass storage from the NCK (Numerical Control Kernel) working memory. Two physically distinct media cooperate whenever an NC program is edited, executed, or archived:

• PCU 50.3 hard disk – a Windows-based partition scheme rooted at F:\ that holds the editable copies of all part programs, workpieces, and tools.
• NCU static memory – battery-backed SRAM inside the Numerical Control Unit that holds the currently active (loaded) program image used by the interpolator.

Operators interact only with the F:\ tree; the NCU SRAM is populated by an automatic load/unload protocol that the HMI software triggers in response to Load, Unload, Select, and Execute actions. Understanding that protocol is the prerequisite for any successful recovery of a deleted .mpf, .spf, or .wpd.

The active runtime for the architecture described in this reference is HMI v7.30.45 SP2 running on a PCU 50.3, paired with an NCU 7x0.x or NCU 710.x. Newer controller generations (NCU 730.3, SINUMERIK ONE) replace this scheme with CFast-based or SSD-based storage, but the load/unload semantics described here still apply conceptually.

2. PCU 50.3 Hardware and HMI v7.30.45 SP2 Environment

The PCU 50.3 (Type 6FC5210-0DF31-2AA0 in the standard configuration) is an industrial PC with a CompactFlash or HDD subsystem that boots Microsoft Windows Embedded Standard 7. The HMI v7.30.45 SP2 runtime is installed on top of the operating system. The relevant storage characteristics are:

3. F: Partition Layout and Program Directories

The F:\ partition follows a strict directory convention enforced by the HMI shell. Programs are only displayed in the program manager when they reside in one of the recognized paths:

F:\
├── dh\
│   ├── wks\
│   │   ├── workpiece_001\
│   │   │   ├── wpd\
│   │   │   │   ├── program.mpf
│   │   │   │   └── subroutine.spf
│   │   ├── workpiece_002\
│   ├── cus\
│   │   └── (manufacturer cycles)
│   ├── cma\
│   │   └── (manufacturer macros)
│   └── arp\
│       └── (archive sub-directories)
└── (other HMI user data)

The wks tree corresponds to the Workpieces entry in the HMI program manager. Each workpiece has its own subdirectory containing a wpd folder that holds the executable .mpf and any number of .spf sub-program files. The HMI scans this tree on startup to populate the selection list, which is why deleted files stop appearing immediately in the operator area.

3.1 Recognized File Extensions

4. NC Program File Types: mpf, spf, wpd/wks, and Archives

An NC program in SINUMERIK nomenclature is one of three logical objects:

• Main program (mpf) – the entry point for part execution. The HMI runs a single mpf at a time.
• Sub-program (spf) – a callable block of code referenced via L or CALL statements from the mpf or from other spf files. Sub-programs can be deeply nested.
• Workpiece directory (wpd / wks) – a logical container that groups an mpf with the spf files and metadata (tools, setters, comments) belonging to a single part. The HMI requires a workpiece container for program selection; a loose mpf without a wks parent can be selected but loses tool data.

The archive (.arc) is a binary snapshot generated by the HMI Commissioning > Create NC archive function or by the SAVE command on the CF card. Archives are not loaded into the NCK; they are unpacked back to F:\dh\wks only.

5. Program Lifecycle: From Hard Disk to NCU Static Memory

The HMI uses a state machine to keep the F: directory and the NCU SRAM in sync. There are four observable states for any given program file:

1. Not loaded – file exists on F:\dh\wks only. Visible in program manager; not active.
2. Selected – the HMI has staged the file in the NCK working memory but has not committed it to static memory. Selecting the same program again is a no-op.
3. Loaded – the file is in NCU static memory; F: copy remains as the source of truth. Editing through the HMI updates both copies atomically.
4. Unloaded – the file is removed from NCU SRAM; the F: copy remains. Triggered by an explicit Unload action, by a Reset, or by power-off if battery is dead.

The user-visible rule is: anything you see in F:\dh\wks is not currently in the NCU; anything currently executing is not in F:\dh\wks. This rule is the basis for both backup and recovery.

6. File Deletion Mechanics and the Windows CE Recycle Bin

The HMI's program manager is a thin shell that delegates filesystem operations to the underlying Windows Embedded file system. Deleting a workpiece directory therefore does not issue a raw unlink; it uses the standard Windows Recycle Bin mechanism:

1. Operator highlights a workpiece in the HMI program manager.
2. The shell prompts: "Are you sure you want to remove the folder xxxx and move all of its components to the Recycle Bin?"
3. If the operator confirms, the directory tree is moved into RECYCLER on the same drive.
4. The data is recoverable from the Recycle Bin only as long as the operator has not run Empty Recycle Bin or as long as the bin has not exceeded its size quota.

7. Why Standard Recovery Tools Fail on the F: Partition

Several factors make consumer forensic tools (PhotoRec, Recuva, commercial undelete utilities) unlikely to recover deleted NC programs on a PCU 50.3:

The combination of these conditions is why low-level carving (for example, signature-based searches for the %_N_ NC identifier at the head of every program block) returns no matches even on drives that were not encrypted. The blocks are physically intact but logically re-allocated by the time the operator attempts recovery.

8. NC Archive Backup: Restoring Programs from WINPCIN Splits

The supported recovery path is restoration from an existing NC archive. The HMI v7.30.45 SP2 Commissioning menu creates archives as a single .arc file that can be split into individual program files for transfer back to a PCU. The transfer utility is WINPCIN.

8.1 Generating a Split Archive

1. On the HMI: navigate to Start > Commissioning > NC Archive.
2. Select Create NC archive. The HMI builds a binary archive on the active CF card or in F:\dh\arp.
3. Copy the resulting .arc file to a USB stick or a network share accessible from the engineering PC.

8.2 Splitting the Archive with WINPCIN

1. Install WINPCIN on the engineering PC (Microsoft Windows; available on the SINUMERIK tool CD or as a free download from the Siemens support portal).
2. Launch WINPCIN. Select File > Open Archive and choose the .arc file.
3. Use Archive > Split Archive to expand the binary archive into individual .mpf and .spf text files. Each file is given its original workpiece directory structure.
4. Inspect the output directory. Each text file begins with a %_N_ identifier that includes the program name and path, which can be cross-referenced to the original F: layout.

8.3 Restoring to the PCU

1. Reconnect WINPCIN to the PCU over Ethernet (default port 1900) or RS-232 (default 9600 8N1).
2. Select File > Send > NC Program and push the previously split files into F:\dh\wks\<workpiece_dir>\wpd\.
3. Verify the HMI program manager refreshes and the workpiece reappears.

Detailed WINPCIN field procedure is documented in the SINUMERIK Operate Programming and Operating Manual, available through the Siemens Industry Online Support portal. Archive handling semantics are covered in the SINUMERIK 840D sl Commissioning Manual, also at the same Siemens Industry Online Support site.

9. Preventive Backup Strategy and Versioning Workflow

Because forensic recovery on the F: partition is unreliable, the only field-proven approach is to capture archives on a fixed schedule. Recommended policy:

• Daily incremental – HMI Create NC archive scheduled via the HMI's batch planner; output pushed to a UNC path on the shop floor server.
• Per-shift full – same procedure but full archive (include all workpieces), retained 30 days.
• Per-tool-change full – triggered by an HMI tool change event in the program list, capturing the program set associated with the new tool.
• Pre-edit snapshot – any time an operator opens the editor, the HMI automatically writes a *.bak to the same directory; do not disable this in systemconfiguration.ini.

10. File Transfer Utilities and Connectivity

Always confirm the PCU 50.3 firewall rules permit the chosen transport before starting a recovery; by default, the HMI blocks inbound TCP 1900 and requires explicit activation in System > Network > Firewall.

11. Verification Checklist After Recovery

1. Confirm the restored workpiece appears in HMI > Program Manager > Workpieces with the correct name and last-modified date.
2. Open each mpf and spf in the HMI editor and verify the first line begins with %_N_<name>_<path>.
3. Select the workpiece, then Load, and confirm the HMI log records the load operation without error (look for NCK error 0 in the diagnosis log).
4. Execute a dry run (single block) of the restored program with the spindle disabled to confirm runtime behavior.
5. Trigger a new NC archive and verify the restored programs are captured in the resulting .arc file.

If any step fails, re-verify the source archive integrity by re-running the WINPCIN split and checking the output .arc checksum against the original.

12. Related Configuration Files and Diagnostic Paths

The following HMI-side files are useful when diagnosing deletion or recovery issues:

• F:\dh\wks\<workpiece>\wpd\*.mpf / *.spf – operator program source.
• C:\Program Files (x86)\Siemens\Automation\SINUMERIK_Operate\systemconfiguration.ini – controls Recycle Bin, auto-archive, and editor behavior.
• F:\dh\arp\*.arc – current archives.
• F:\dh\cus\*.com – manufacturer cycles, also subject to the same deletion rules.
• F:\user\<operator>\ – per-operator settings, not typically subject to the program lifecycle.