What is the CNC file format?
.cnc files in Dolphin PartMaster are proprietary binary project files produced by Dolphin PartMaster CAD/CAM, a computer-aided manufacturing system developed by Dolphin CAD CAM Systems. The file stores the intermediate CAM stage of a machined part - tool selections, feeds and speeds, toolpath operations, and machining strategy data derived from a CAD geometry drawing.
The typical Dolphin PartMaster workflow begins with a CAD drawing saved as a .DRA file, which is processed in the CAM module to produce the .cnc project file. A post-processor then converts the .cnc file into G-code output stored as a .pun file for transfer to the CNC machine controller. The .cnc file is proprietary binary and is not human-readable.
Dolphin CAD CAM Systems remains an active company (dolphincadcam.com). PartMaster supports milling, turning, and wire EDM operations.
Important: the .cnc extension is also used far more widely as a generic label for CNC G-code programs - plain-text files containing ISO 6983 (RS-274) machine commands, interchangeable with .nc, .tap, and .gcode. In that generic context, .cnc files are readable in any text editor. This article describes the specific Dolphin PartMaster binary usage.
Security & safety
RISK: LOWCNC/CAM files are data files without executable code. A maliciously crafted G-code file could command a CNC machine to move unsafely (tool crash, over-travel), but this requires physical access to the machine. No known malware vector via .cnc files on PC.
Format details
in a nutshell- Generic CNC/G-code Program - Many CNC machine controllers (Fanuc, Mach3, GRBL etc.) save and load G-code programs as .cnc - plain ASCII text with ISO 6983 (RS-274) G-code commands; no relation to Dolphin PartMaster.
- CNC Toolkit / Generic CAM Output - Various CAM packages (ArtCAM, Mastercam, Fusion 360 post-processors) can output .cnc as a synonym for .nc/.tap G-code files.
Programs that open CNC files
Windows3 apps
Dolphin Cad Cam PartMaster
Paid File → Open, select the .cnc file; PartMaster displays the CAM operations and toolpath.
Notepad (for generic G-code .cnc files)
Built-in Right-click → Open with → Notepad; readable only if the file is plain-text G-code.
QuickCAM 2D (Denford)
Paid Open .cnc files generated by Denford QuickCAM; Denford-specific tool path format. Technical details
deep spec| Encoding | Binary (proprietary Dolphin PartMaster format) |
| Byte order | Little-endian (Windows-native application) |
| Container | Proprietary Dolphin PartMaster CAM project container |
| Magic bytes | None publicly documented - proprietary binary format |
| Compression | No compression documented; format internals are proprietary |
| Typical file size | 10 KB - 5 MB (depending on part complexity) |
| CAM workflow role | Intermediate stage between CAD drawing (.dra) and post-processed G-code output (.pun) |
| Stored data | Tool selections, feeds, speeds, toolpath operations, and machining strategy data |
| Supported operations | Milling, turning, wire EDM (within Dolphin PartMaster) |
| Platform | Windows only |
| Extension ambiguity | .cnc is also widely used as a generic G-code extension (plain ASCII text, ISO 6983/RS-274) by many CNC controllers - unrelated to this proprietary Dolphin format |
| Released | 1990s (Dolphin PartMaster early versions) |
| Specification | www.dolphincadcam.com |
CNC conversions
Community Q&A
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