What CNC Files Are
CNC (Computer Numerical Control) files provide machine-readable fabrication data for automated steel processing equipment — saws, drill lines, coping machines, and plasma cutting tables. In structural steel, 'CNC files' typically refers to DSTV files (Deutsches Institut für Normung Stahlbau-Verband format), though DXF and proprietary formats are also used depending on the equipment manufacturer.
The DSTV / NC1 File Format
DSTV format (also called NC1) is the industry-standard machine exchange format for structural steel CNC data. A DSTV file contains: the member's section profile (per European or AISC section database), member length, all hole groups with exact X-Y coordinates, coping and notching instructions, and the piece mark identifier. Most modern structural steel processing equipment — Ficep, Peddinghaus, Voortman, Scotchman — reads DSTV natively.
- Section profile code — must match the machine's section library
- Member length — to the nearest millimeter or 1/16"
- Hole groups — X-Y coordinates from member origin, bolt diameter, and hole tolerance
- Coping definitions — cope start, depth, length, and corner radius
- Piece mark — links the NC file to the shop drawing
How CNC Files Are Generated from Tekla
Tekla Structures generates DSTV NC1 files directly from the model through the NC/DSTV export function. The accuracy of the NC file is only as good as the model — every connection plate, bolt hole, and cope in the model must be built correctly for the exported NC file to be fabrication-ready. Common model errors that produce bad NC files: hole diameters set to the bolt diameter instead of the required hole clearance; copes built as geometry without the NC1 parameter assigned; section profiles coded to a Tekla section that does not match the machine's section library.