DSTV NC1 · Steel Fabrication · EN 1090-2
DSTV NC1 Export Guide
The Format Reference That Turns Your PDFs Into CNC-Ready Files
Introduction
What is DSTV NC1 — and Why Does It Cost You Hours?
DSTV NC1 is the standard file format for passing structural steel geometry from CAD/BIM tools to CNC drilling and cutting machines across Europe. If you work with industrial steel — portals, frames, trusses — you've dealt with NC1 files. Most fabricators spend 2–4 hours per project manually translating drawing data into NC1 format. That's time that could go into fabrication. The format is well-documented — DSTV (Deutscher Stahlbau-Verband) published the 7th edition spec in 2002 — but the practical guidance on what actually goes into a correct NC1 file, and why import errors happen, is scattered across manufacturer docs and forum threads. This guide fixes that.
Worked Example
Worked Example: 24 m Portal Frame
A single-span portal frame with haunches. Two columns (HEA300, 5.5 m), two rafters (IPE400, 12 m each, 15° pitch), base plates, apex connection. Total: 18 parts. Here's how the NC1 file is structured — from ST (profile list) through to the last PU (punching) block.
Generated NC1 (partial — ST + SI + AK + KA + BO blocks)
Full DSTV NC1 export from your own PDFs — FrameAI reads the drawing and writes the NC1 file automatically. See Pro →
Format Reference
Spec Deep-Dive: The 7 Block Types
Block Type Reference
NC1 uses a right-handed Cartesian system with X as the primary axis. All dimensions are in millimetres with 1 decimal place. The origin is typically at the bottom-left of the structural system, but any local origin is valid as long as all blocks reference it consistently. Coordinate values are always integers (stored as tenths of mm — 100 = 100.0 mm).
All lengths in mm. Angles in degrees with up to 3 decimal places. Character encoding is ASCII (ISO 646). The ST block opens every file and the EN block closes it. Fields are fixed-width and space-padded — trailing spaces are significant in some importers.
Troubleshooting
Common Import Errors and FrameAI Prevention
These errors appear in CNC control logs across Europe. FrameAI generates NC1 files that pass all of them automatically.
| Error | Root Cause | FrameAI Prevention |
|---|---|---|
| Neutral axis offset in BO block | BO coordinates use member neutral axis, not outer profile face. FrameAI uses correct neutral-axis transformation. | FrameAI calculates neutral-axis coordinates from section geometry automatically. |
| Hole position outside part profile | AK/KA origin and part origin mismatch — hole coordinates reference wrong local system. | FrameAI retains consistent origin from AK through all child blocks. |
| Duplicate profile marks in ST block | Multiple KA blocks referencing the same profile without de-duplication in ST. | FrameAI de-duplicates ST block entries before writing. |
| Invalid integer coordinate in BO block | Floating-point coordinates not converted to tenths-of-mm integer format. | FrameAI enforces integer encoding for all coordinates. |
| PU block after KO — sequence violation | Blocks out of required DSTV sequence order (ST → SI → AK → IK → KA → BO → AB → KO → PU → WN → EN). | FrameAI enforces correct block sequence in generation. |
| ST block missing for referenced profile | KA block references a profile not defined in the ST block. | FrameAI resolves all profile references before writing ST block. |
All 12 DSTV NC1 validator checks are implemented in services/fabrication/dstv/validator.js.
FrameAI runs them automatically before releasing any NC1 export.
Free Download
Download the Full 4-Page DSTV NC1 Spec
The complete reference: format specification, worked 24 m portal frame example, EN 1090-2 fabrication tolerance context, and the 6 import errors.
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