DXF and STEP are the two formats you meet most in sheet metal. They are not interchangeable. Using the wrong one wastes time on both sides. Here is the clear rule.
The fundamental difference
DXF is 2D. STEP is 3D. That single fact decides almost everything.
- A DXF describes flat contours — exactly what a cutting machine reads.
- A STEP describes a volume — exactly what CAD software needs to design and validate.
DXF — the cutting format
DXF (Drawing Exchange Format) is the universal 2D format for cutting. Every laser, waterjet and plasma machine reads it. When a shop asks you for "the file" to cut a part, they want a DXF.
A clean cutting DXF contains only the closed contours to be cut — nothing else. No dimensions, no duplicate lines, no construction geometry.
The common trap: a DXF exported carelessly contains open polylines, duplicate lines, or dimensions mixed into the geometry. Such a file is unusable on a machine and must be cleaned first.
STEP — the validation format
STEP is the universal 3D exchange format. It opens in every CAD package: SolidWorks, Fusion 360, CATIA, Onshape. In sheet metal, you use STEP to validate the part in 3D before manufacturing, and to check how it fits in an assembly.
But a cutting machine does not read a STEP. To cut a part defined as a STEP, you first have to unfold it — extract the 2D flat pattern, which then becomes a DXF.
When to use which
| Situation | Format |
|---|---|
| Send a part to be cut | DXF |
| Validate a 3D model | STEP |
| Check an assembly fit | STEP |
| Feed a laser or waterjet machine | DXF |
| Exchange between two different CAD tools | STEP |
The unfolding step
The bridge between the two worlds is unfolding: taking a 3D part (STEP) and computing its 2D flat pattern (DXF), K-factor included. This is the operation that turns a designed model into a manufacturable file.
DRAWLESS bridges the two
DRAWLESS accepts both. Import a STEP and the engine automatically extracts the 2D flat pattern. Describe a part in plain language and DRAWLESS generates both a clean cutting DXF and a 3D model at once. You stop juggling formats — you describe or import, and DRAWLESS produces what each stage needs.