STEP (.step) is a parametric CAD file that contains the exact geometry and feature history — ideal for production and machining. STL (.stl) is a mesh file: a triangle approximation of the surface, smaller and universal but without feature data. For 3D printing both work; for maximum precision and CAD edits, choose STEP.
When do you choose STEP?
STEP (Standard for the Exchange of Product Data, ISO 10303) contains the full NURBS geometry of your design: exact curves, surfaces and feature relations. For 3D printing this means the slicer sees the true surface, not an approximation. Result: smoother round shapes and tighter fits — especially noticeable in parts with cylinders, cones or spheres.
STEP is also editable: our engineers can check wall thickness, shell cavities, or add features without re-modelling the geometry. For parts that will later be machined (thread tapping, press-fit, assembly), STEP is necessary to guarantee exact dimensions.
Most CAD packages (Fusion 360, SolidWorks, Inventor, NX, Creo, Onshape) export to STEP by default. Choose STEP AP242 or AP214 for maximum compatibility.
When do you choose STL?
STL (STereoLithography) was the first 3D-printing file format and remains universally supported. An STL consists of thousands of triangles approximating the surface — at high resolution that difference is invisible, at low resolution you see facets on curved surfaces.
Choose STL when:
- The design comes from a mesh tool (Blender, ZBrush, Rhino meshes)
- It’s scan data (3D scans to mesh)
- You have topology-optimised or generative designs, often only exportable as mesh
- You need a lightweight version for a fast quote — STL files are typically 5-10x smaller than STEP
Export at high tolerance (chord deviation 0.01 mm or lower) to avoid facet artefacts.
Other file formats
Besides STEP and STL we accept 3MF, OBJ, IGES and x_t (Parasolid). 3MF is a modern STL successor with support for colour and material assignment per face — for multi-material or coloured prints this is the right format. OBJ is mainly used for visualisations and 3D scans.
Not accepted: PDF drawings, 2D drawings only, or photos. For reverse-engineering a physical part without STEP, you need a 3D scan — our engineers can refer recommended scan bureaus or scan on-site.