SliceLoft
How to convert STEP to STL
- Open your CAD model. Choose a .step or .stp file, or a ZIP containing CAD models. The STEP engine downloads only when you open a file or load the sample.
- Choose mesh precision. Start with Standard, inspect curved surfaces and check the dimensions in millimeters. Use Coarse for smaller files or Fine for more detail; advanced settings let you enter your own tolerances.
- Download STL. Export one combined STL or a ZIP with one STL per part. Binary is the default; ASCII is also available. Check the resulting mesh and slicing preview before printing.
STEP vs STL: precise surfaces and triangle meshes
STEP preserves CAD geometry as mathematically defined surfaces and solids. STL approximates the outer surface with flat triangles. This conversion is called tessellation: it makes a mesh that slicers and mesh editors can process, but it does not retain the original parametric CAD design.
Many printing workflows use meshes to calculate layers and toolpaths. A slicer that accepts STEP can create that mesh during import, so a separate STL conversion is not always necessary. Keep your original STEP for future CAD editing.
How to choose mesh precision
Coarse prioritizes speed and a smaller download; curved surfaces may look faceted. Standard is a starting point for everyday models. Fine uses tighter tolerances and usually creates more triangles, increasing processing time, memory use and file size. A box with only flat faces may have the same triangle count at all three settings.
Linear deflection is the allowed distance between the CAD surface and its mesh approximation, in millimeters. Angular deflection limits angular deviation, in radians. Smaller values generally create finer meshes. Check curves at the scale you intend to print; a larger mesh alone does not guarantee a better print.
Units and assembly parts
By default, the file’s declared units are converted to millimeters. The optional unit override rescales the already normalized coordinates: centimeters multiply by 10, meters by 1,000 and inches by 25.4. Leave it on File units unless you deliberately need to correct the scale. STL has no unit field, so import the result as millimeters.
Part names and triangle counts help you inspect an assembly. Combining parts puts their triangles in one STL without performing a boolean union. Separate downloads preserve each part’s placement and use safe, distinct filenames. CAD colors are for preview only; STL contains geometry, not colors or materials.
IGES (.igs/.iges) is also supported. IGES models may contain separate surfaces that produce open edges after meshing. Prefer STEP when available, and check or repair the exported mesh in your slicer before printing.
Frequently asked questions
Can I import STEP directly into Bambu Studio or PrusaSlicer?
Yes. Bambu Studio and PrusaSlicer can import STEP directly. Free Cura supports mesh formats such as STL and 3MF. Official STEP and IGES import requires a paid UltiMaker software plan and Cura 5.11 or later. The plugin is included automatically in Cura Enterprise 5.11 or later; free software plans cannot use it. Converting to STL is useful if your Cura installation lacks CAD import, a print service requests STL, or you need a mesh editor.
Are my STEP files uploaded?
No. CAD parsing, meshing, preview and STL export run locally in your browser. The engine is downloaded to your device; your model files are not uploaded for conversion. Feedback you choose to submit is sent separately.
How are assemblies and failed parts handled?
The tool lists the parts returned by the CAD importer with their triangle counts. Export them together or as separate STL files in a ZIP. Parts identified as unable to produce a usable mesh are skipped with a warning; remaining parts can still be exported. Inspect the preview and part list for missing geometry before printing.
Why does the first conversion take longer?
The CAD engine downloads only after you select a file or load the sample. Its WASM file is about 7.6 MB uncompressed; with server compression, the transfer is about 3 MB. Actual transfer size depends on the hosting platform and browser. Later loads may use the browser cache; clearing it or changing browsers can require another download. Complex models also take time to mesh.
Why is the STL large, or why did the browser run out of memory?
Fine settings and complex assemblies can produce many triangles. Try Coarse, relax the advanced tolerances, or export a smaller source assembly. More than 2 million triangles triggers a warning. A file below the 200 MB input limit can still exceed the memory available on your device.
Does conversion repair a model or guarantee it will print?
No. Degenerate triangles, open edges and non-manifold edges are reported without automatic repair. Inspect and, if needed, repair the exported mesh in your slicer or modeling software. Check size, missing parts, supports and the slicing preview before printing.
UltiMaker STEP and IGES import requirements