A client sends a DWG, the shop asks for a DXF, the design office works in STEP. Three formats, three uses. Here is which one does what.
The basic distinction: 2D or 3D
First, you have to separate two families. 2D formats describe flat contours — that is what a cutting machine needs. 3D formats describe a volume — that is what CAD software needs to design and validate. Confusing the two is the source of most file-exchange errors.
DXF — the universal 2D exchange
DXF (Drawing Exchange Format) is the king format for cutting. It is a 2D, open format, readable by every laser, waterjet and plasma machine. When a shop asks you for "the file", they almost always want a DXF.
DXF is to the cutting file what PDF is to the document: a universal standard everyone can open.
Its trap: a poorly made DXF — open polylines, duplicate lines, dimensions mixed into the contour — is unusable on a machine and must be cleaned. A good cutting DXF contains only the closed contours to be cut.
STEP — the reference 3D exchange
STEP (Standard for the Exchange of Product model data) is the universal 3D exchange format. Unlike the proprietary formats of CAD software, STEP opens everywhere: SolidWorks, Fusion 360, CATIA, Onshape. It is the format to use to transmit a 3D model between two parties who do not have the same software.
In sheet metal, STEP is used to validate the part in volume before manufacturing, and to check assemblies. But a cutting machine does not read a STEP: you have to extract the 2D flat pattern from it.
DWG — AutoCAD's native format
DWG is AutoCAD's native format. It is a rich, mainly 2D format that contains the complete drawing: contours, dimensions, layers, text, blocks. Many design offices and architects work in DWG.
Its problem for sheet metal: it contains far more than the contour to be cut. Before cutting, you have to extract the useful geometry and convert it to a clean DXF. It is a working and drawing format, not a cutting format.
IGES — the old 3D standard
IGES is the ancestor of STEP for 3D exchange. You still encounter it, but it is gradually being abandoned in favor of STEP, which is more reliable and complete. If you have the choice, prefer STEP.
The summary table
| Format | Dimension | Main use | For cutting? |
|---|---|---|---|
| DXF | 2D | Machine cutting | Yes, directly |
| STEP | 3D | 3D exchange and validation | No, unfold first |
| DWG | 2D (rich) | Drawing, plan, archiving | No, clean first |
| IGES | 3D | 3D exchange (old) | No, unfold first |
Which format to ask for, which to provide
- You send a part to be cut to a shop → provide a clean DXF.
- You want a 3D model validated → exchange in STEP.
- You archive a complete dimensioned drawing → DWG or PDF will do.
- A client sends you a DWG or a STEP → you will need to extract the cutting DXF.
DRAWLESS handles conversions for you
DRAWLESS accepts a natural-language description, but also DXF and STEP file imports. From a 3D STEP, the engine automatically extracts the 2D flat pattern. From a description, it directly generates a clean cutting DXF, drawings and a 3D model. You no longer have to juggle formats: you describe or you import, DRAWLESS produces what the shop needs.