Your STEP File Converts to a Broken STL? Repair It Before It Is Meshed.
Small gaps sewn and broken faces fixed, in the same conversion.
STEP and IGES store solids as B-Rep surfaces. Tiny gaps between faces, unsewn edges, and wire tolerance errors turn into open edges and non-manifold geometry that PrusaSlicer, Cura, Bambu Studio and Orca reject. 3D CAD Converter runs OpenCascade shape healing on the B-Rep before it tessellates, so small gaps are closed before they become open edges, across a whole folder at once.
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Without 3D CAD Converter
- Slicer throws 'non-manifold' or 'not watertight' and refuses to slice
- Gaps and open edges you can't see until the print fails
- Round-tripping through Meshmixer or Netfabb, one file at a time
- Uploading proprietary CAD to a web repair site
With 3D CAD Converter
- B-Rep healed before meshing, so small gaps no longer become open edges
- Gaps sewn, wires and faces fixed
- Entire folders repaired in one batch run
- 100% offline — your CAD never leaves your machine
What the repair pass fixes
OpenCascade sewing seals tolerance gaps so surfaces form one closed shell instead of loose sheets.
ShapeFix healing repairs wireframe and face defects that would otherwise become non-manifold edges in the mesh.
Repair closes gaps and fixes how faces join. It does not move surfaces or rescale the part.
Repair a single part or a folder of hundreds. Wire it into a pipeline with the --repair CLI flag.
Repair runs on the STEP/IGES → STL path
Because STEP and IGES carry the true B-Rep solid, we heal the geometry at its source — before it ever becomes triangles. Turn on Repair in the wizard, or pass --repair on the CLI, and each file gets:
- ✔ Shape healing (ShapeFix) on the whole solid
- ✔ Wireframe fixing to close small edge gaps
- ✔ Per-face fixing and sewing into a closed shell
- ✔ Tessellation to STL, OBJ or PLY
Note: repair works on STEP, IGES and BREP sources during conversion. It closes small gaps in the solid before meshing. It is not an editor for an STL that is already broken, and gaps too wide to sew need a fix in the source CAD file.
Watch a STEP file become a print-ready STL
How It Works
Download & Install
Free trial: 10 conversions with every feature. Windows 10/11.
Enable Repair
Add your STEP or IGES files, pick STL, and tick Repair. Choose a tessellation preset for smoothness.
Click Convert
Every file is repaired, then tessellated to STL: the whole folder in one run.
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|---|---|---|
| Netfabb | Subscription (annual renewal) | |
| CAD Exchanger | Subscription (annual renewal) | |
| 3D CAD Converter | $179 | ✔ Pay once, own forever |
Free trial: 10 conversions with every feature. No credit card required. Windows 10/11.
STEP to STL repair — FAQ
Why does my STEP file convert to a non-manifold STL?
STEP and IGES store solids as B-Rep surfaces. When those surfaces have tiny gaps, unsewn faces, or wire tolerance errors, the tessellated STL inherits open edges and non-manifold geometry that slicers reject. Enabling Repair runs OpenCascade shape healing on the B-Rep before tessellation, which closes the small gaps before they reach the STL.
What exactly gets fixed during repair?
Repair heals the B-Rep solid before it becomes triangles: it sews gaps between unconnected faces, closes small wire and edge tolerance errors, and fixes per-face defects. Where the gaps are small enough to sew, the faces join into a closed shell and the STL, OBJ or PLY has no open edges there.
Can it repair an STL that is already broken?
No. 3D CAD Converter heals the geometry at its B-Rep source, so the input must be a STEP, IGES or BREP file. It is not a standalone STL editor: if you only have an already-broken STL, there is no exact solid left to heal from. Convert from the original STEP or IGES with Repair enabled, or fix the STL in a mesh editor.
Will repair change the shape or dimensions of my part?
No. Shape healing only closes gaps and fixes topology within the file's own tolerances; it does not move surfaces or rescale the part. Your dimensions are preserved — repair changes how the solid is stitched together, not what the solid is.
Does repair work on a whole folder at once?
Yes. Turn on Repair once and it applies to every file in the batch. Drop a folder of STEP or IGES files, choose STL as the output, and each one is repaired and exported, entirely offline, with no upload.