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Guided workflow variation

Coming soon for Windows. Feature preview.

Repair a broken STL file,and see every change first.

MeshMedic opens the STL, counts its holes, non-manifold edges, and inverted triangles, fixes them in one step, and paints every changed triangle blue so you can check the repair before a new file is written.

Open the STL, choose Repair, check the blue patches and the Before and After counts, then export a new STL beside the original.

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If this sounds like your week

The slicer flags the model, and the part is due tonight.

An STL is nothing more than a long list of loose triangles. Exporters, downloads, and quick edits leave gaps where faces went missing, triangles wound the wrong way, and corners where too many faces meet. The slicer then warns about errors, drops a wall, or fills a cavity it should leave empty, and the toolpath preview stops matching the part you designed.

Where tooling usually breaks

Fixing it blind costs filament and an evening.

Rebuilding the model in CAD can take longer than the job itself, and often nobody has the source design anymore. A large modeling suite asks you to learn a whole toolbox for one chore. Web repair sites want the customer's file on their server. And an automatic fix that reports nothing leaves you guessing whether the shape you send to the machine is still the shape you were given.

Where MeshMedic lands

Count the defects, repair them, check the result, then export.

MeshMedic reads binary or ASCII STL and lists each defect with a Before count. Choose Repair and the After column fills in while the 3D view paints every flipped or added triangle blue. Toggle Show before to compare. When it looks right, Export writes a new STL in the same flavor, and a short note records what was flipped, added, removed, welded, and split.

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What you get

Feature highlights

Every defect counted

non-manifold edges, inverted triangles, and holes for every part, in a table with Before, After, and Status columns, and No defects found for a clean file.

One repair pass

welds coincident vertices, removes degenerate and duplicate triangles, splits non-manifold edges and vertices, orients every shell outward, and caps holes.

Every change shown in 3D

triangles the repair flipped or added turn blue, and Show before switches back to the mesh as it was, with inverted triangles in red.

3MF projects kept intact

colors, materials, components, build items, metadata, and the thumbnail come through, and only the repaired mesh is rewritten.

A before and after note

the counts for every part and the triangles flipped, added, and removed, ready to copy or save as a .txt file for the job.

Originals never overwritten, nothing uploaded

every export is a new file in the same format, and the app makes no network connections and has no account.

Especially when

  • Repair holes, non-manifold edges, and inverted triangles in an STL, OBJ, or 3MF without rebuilding the model in CAD
  • See exactly what a repair changed, with counts before and after and every changed triangle shown in 3D
  • Repair a 3MF in place, keeping its colors, materials, components, and plate layout instead of converting it to STL
  • Keep customer and client models on the PC, with no upload, no account, and the original file never overwritten

Who benefits

Real-world scenarios

A downloaded model that will not slice cleanly

A maker downloads a bracket from a model-sharing site. The slicer warns about errors, and the layer preview shows a missing patch on the top face where two triangles were never exported.

MeshMedic lists Holes 2 and Inverted triangles 4 as Found. After Repair, both rows read 0 and Fixed, the new caps show in blue, and Export writes bracket-repaired.stl next to the untouched download.

A print shop checking a customer file

A customer emails an STL exported from an older CAD package for a same-day job. The shop wants to know what is wrong with it before anyone touches the slicer settings or quotes the time.

The operator opens the file, reads the Before counts, repairs it, and saves the note as a .txt file with the job. If the customer asks what changed, the note lists the counts before and after and every flipped and added triangle.

An ASCII STL written by a script

An engineer generates parts as ASCII STL from a script. One generated part has its faces wound the wrong way, so the slicer treats the part as inside out.

MeshMedic reads the ASCII file, flips the inverted triangles so every shell faces outward, and writes the export as ASCII STL again, so the rest of the pipeline reads it the same way it read the original.

Deep dive

What an STL repair changes, step by step

Reading the file. MeshMedic opens binary and ASCII STL. Because STL stores every triangle with its own three corners, it first welds corners that sit at the same position, so the counts describe the real surface rather than a pile of separate triangles. The file label shows the name, the format, the number of parts, and the triangle count.

Counting the defects. The table has four columns: Defect, Before, After, and Status. Non-manifold edges are edges shared by three or more triangles. Inverted triangles face the wrong way compared with the rest of their shell. Holes are closed loops of open edges. Degenerate and duplicate triangles get a row of their own when the file has any. A clean file shows "No defects found".

The repair. Choose Repair and MeshMedic runs one pipeline: it welds coincident vertices, removes zero-area and duplicate triangles, splits non-manifold edges and vertices, clears away stray fragments too small to enclose a volume, turns every shell so it faces outward, and caps holes with new triangles that face the same way as their neighbors. The mesh as it was stays in memory, so Show before can still draw it.

Checking it in 3D. The preview draws triangles the repair flipped or added in blue, labeled Changed by repair. Drag or use the arrow keys to orbit, scroll or press plus and minus to zoom, and press Home to reset the view. Show before switches between the mesh as it was, with its inverted triangles in red, and the repaired mesh.

Writing the export. Export opens the Windows save dialog with a suggested name, such as bracket-repaired.stl. A binary STL is written as binary and an ASCII STL as ASCII. Each kept triangle carries its attribute bytes across, which some programs use for color, and normals are recomputed from the corrected winding.

Keeping a record. After the export, the note shows the source and export names, the counts before and after for every part, and the changes: triangles flipped, added, and removed, and vertices welded and split. Copy puts it on the clipboard, and Save note writes it as a .txt file.

Launch updates. MeshMedic is coming soon for Windows. Use the waitlist form on the product page and confirm your email address to hear when it launches. No payment is taken.

Feature preview

Explore the intended workflow

Every defect counted

non-manifold edges, inverted triangles, and holes for every part, in a table with Before, After, and Status columns, and No defects found for a clean file.

One repair pass

welds coincident vertices, removes degenerate and duplicate triangles, splits non-manifold edges and vertices, orients every shell outward, and caps holes.

Every change shown in 3D

triangles the repair flipped or added turn blue, and Show before switches back to the mesh as it was, with inverted triangles in red.

FAQ

Straight answers—no glossary dump

How do I repair an STL file with MeshMedic?

Choose Open file and pick the STL. MeshMedic counts its non-manifold edges, inverted triangles, and holes in the table. Choose Repair, check the After column and the blue triangles in the 3D preview, and use Show before to compare. Then choose Export and save a new file; MeshMedic suggests the original name with -repaired added. The before and after note appears as soon as the export is written.

Which STL defects does MeshMedic repair?

It repairs non-manifold edges, where three or more triangles share one edge; inverted triangles, which face the wrong way; and holes, which are loops of open edges. Along the way it welds duplicate vertices, removes zero-area and duplicate triangles, and clears stray fragments too small to enclose a volume. The table shows each defect before and after, with a status such as Fixed.

Can it open ASCII STL as well as binary?

Yes. MeshMedic reads binary and ASCII STL, including ASCII files with Windows, Unix, or classic Mac line endings and facets written on a single line. The export keeps the same flavor: a binary file is written as binary STL and an ASCII file as ASCII STL, so the other tools in your workflow read it the same way they read the original.

What happens to my original STL, OBJ, or 3MF file?

It stays exactly as it was. MeshMedic reads the whole file into memory when you open it and writes every repair to a new file you name in the Windows save dialog, with the original name plus -repaired suggested. Saving over the original is refused, even when you reach it through a shortcut folder (junction), a hard link, a network path, or after it was renamed or moved. You can repair the same original as often as you like.

Where do my files go, and how do I get MeshMedic?

MeshMedic is coming soon to the Microsoft Store for Windows and is not available to download or purchase yet. Use the email form on its product page to join the waitlist, then confirm your email address. We will send launch updates when there is news. No payment is taken.

Related pages

Non-manifold edges, split apart and counted to zero. Fix the mesh errors before the slicer has to guess. STL repair for Windows 11, with nothing uploaded.