STEP file
Also called: STEP · STP · ISO 10303
STEP (.stp/.step) is the most used neutral 3D format for exchanging models between CAD and CAM software without losing solid geometry.
STEP is the format standardized by ISO 10303 for exchanging 3D models. Unlike a native file (SolidWorks, Inventor, NX, Fusion), it opens in virtually any CAD or CAM, and unlike STL it keeps exact geometry as surfaces and solids, not triangles.
How it works
The most common versions are AP203 (basic geometry), AP214 (adds colors and layers, common in automotive) and AP242 (can carry 3D tolerances and annotations, known as PMI). When exporting, the feature history is lost: the recipient sees the final solid but cannot edit the feature tree. For manufacturing that is enough, because CAM works on the surfaces.
Practical example
A customer sends a STEP of a housing plus the PDF drawing. The shop opens the STEP straight in CAM, generates toolpaths and uses the PDF for tolerances and finish. Had the customer sent an STL, holes would arrive faceted and the program would need manual rework.
Common mistakes
- Sending STL for machining, which turns curves into triangles.
- Exporting the whole assembly when only one part will be made.
- Sending the STEP from one revision and the PDF from another.
FAQ
STEP or IGES?
Prefer STEP. IGES is older and handles surfaces well, but often arrives with loose faces and open solids that need repair.
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Related service
CAD engineering
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