STEP and DXF files, explained

STEP or DXF at a glance

What a STEP file is

STEP carries a solid model from one CAD program to another, so the shop doesn't need your software. You may see three versions:

• AP203: mechanical parts and assemblies
• AP214: from car design, adds things like colours
• AP242: combines the two, and can carry tolerances

Ask the shop which one it wants.

Not STL. An STL is a mesh, made mostly for 3D printing. Protolabs discourages STL for machined parts because its software can miss features like pilot holes. Export STEP from your original model. Renaming an STL won't fix it.

What a DXF file is

DXF holds flat lines and arcs: the outline the cutter follows. The shop still needs the material and thickness from you.

• DXF vs DWG: DWG is AutoCAD's own format. DXF is made for moving drawings between programs. Send what the shop asks for.
• Flat only: a DXF can also hold 3D lines, so a .dxf ending alone doesn't make a good cutting file

How to open them for free

Autodesk Viewer uploads your file to Autodesk. Use a desktop tool for parts you need to keep private.

How to make one

A STEP file from your CAD:

• Fusion: File, Export, then pick STEP. The free personal licence keeps STEP export, but it's for non-commercial use.
• SolidWorks: File, Save As, then pick STEP
• Onshape: right click the part, Export, then pick STEP. The free plan makes your files public, so skip it for client parts.
• FreeCAD: select the finished body, then File, Export, and pick STEP

A DXF for cutting:

• Inkscape: set the real size, turn text into paths, then Save As DXF and pick the R14 option
• Illustrator: turn text into outlines, then File, Export, Export As, and pick AutoCAD Interchange File
• Fusion sheet metal: open the flat pattern and use Export DXF. Exporting the whole design gives 3D lines instead.

What shops accept

DXF mistakes that get files sent back

• Open shapes: every outline and hole must close
• Doubled lines: two lines on top of each other get cut twice. Xometry asks for none.
• Notes and borders: dimensions, title blocks and notes can be read as cuts. Leave only what gets cut.
• Text: turn it into outlines. Letters like O and A need small bridges to keep their centres.
• Wrong units: a DXF can say it has no units, so inches can come in as millimetres. Draw at 1:1 and say which units.
• Holes too small: Laseo wants laser cut holes at least 50% of the sheet thickness across
• Splines: some shops want plain lines and arcs, others like SendCutSend take splines. Ask.

Xometry guesses units from the part size: over 48.5 units it reads millimetres, under 1 it reads inches. Check the size in the upload preview before you approve.

Send a PDF drawing too

A model or an outline doesn't show threads, tight tolerances or finish. Add a PDF drawing for those. Protolabs Network requires one for parts with threads or tighter tolerances, and prefers PDF.

More help: what to send a shop and GD&T and tolerances. Ready for a price? Send one request with your file attached.

Sources

• NIST: STEP file analyzer
• SDS2: STEP export
• Adobe: what a DXF file is
• Autodesk viewers
• FreeCAD features and import and export
• Protolabs: CNC design essentials, FAQ and uploading CAD files
• eDrawings Viewer FAQ
• LibreCAD and its manual
• Inkscape manual: free software and importing files
• SendCutSend: DXF from Inkscape and export from AutoCAD
• Onshape pricing and exporting files
• Autodesk: exporting from Fusion and DXF from Fusion
• SendCutSend: STEP from SolidWorks
• FreeCAD: export
• Adobe: exporting from Illustrator
• Autodesk: Fusion personal use
• OSH Cut: DXF for laser cutting
• Xometry file types and preparing DXF files
• Protocase FAQ, Sydney NS
• Ready Set Cut, Mississauga
• Laseo: how it works and 2D drawings, Quebec
• 3FAB Manufacturing waterjet, Calgary
• Precision Laser Works, Barrie ON
• Autodesk: DXF units
• Protolabs Network: manufacturing specs and attaching drawings