XPRTIX 3D
Fix an STL for printing.
Close holes, turn faces the right way round and drop broken triangles, then check the mesh is watertight. Nothing is uploaded.
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Fix an STL for printing: how it works
Why a slicer complains
A slicer needs a mesh that is a closed surface: every edge shared by exactly two triangles, every triangle facing the same way, the inside clearly inside. Models from scans, sculpting tools and quick exports often are not. They have holes, triangles that face the wrong way, degenerate triangles with no area, and repeated ones. The slicer either refuses the file, or guesses and prints a wall that is not there.
The inspector shows how many open edges a model has the moment it is dropped, and offers Repair.
What Repair does
It treats vertices at the same position as one, drops degenerate and repeated triangles, and turns triangles so that every neighbour faces the same way. It then closes holes by triangulating each boundary loop, and turns each closed piece to face outwards if it came out inside out. You choose how big a hole may be: small ones only, or any size up to a couple of thousand edges.
Finally the result is checked with manifold-3d, which accepts only a closed, consistently oriented surface. The card says Watertight when it passes, and says what is still wrong when it does not.
What it cannot fix
Repair does not fix a mesh that passes through itself, edges shared by three or more triangles, or a hole larger than the size you allow. Closing a very large opening, such as the bottom of a scanned object, fills it with a flat patch, which may not be what you want. Look at the result in the viewer before you print.
The check says the mesh is a valid solid. It cannot say your slicer will like it, because slicers differ, so open the result in yours before a long print.
Saving the result
The result is saved as an STL by default, for printing. You can also save it as a GLB, OBJ or any other output the tool writes. Colour and texture are not part of an STL, and are left out.
Transparency
What leaves your device
No model is uploaded. Everything runs in your browser; the compression engines and the validator are downloaded from this site the first time they are needed. What is recorded.
3D guides
Related 3D jobs
Questions
Asked often
What does watertight mean?
Every edge belongs to exactly two triangles and all the triangles face consistently, so the mesh encloses a volume with nothing leaking out.
Will repair change the shape?
It adds triangles to close holes and may turn triangles around. It does not move vertices, so the existing surface is untouched.
Why was a hole left open?
It was larger than the size you allowed, or its edge was not a clean loop, for example where three triangles meet at an edge. Raise the hole size, or fix the area in your modelling tool.
Does it fix self-intersections?
No. Triangles that pass through each other need a modelling tool.
Will my slicer accept the result?
It passes a manifold check, which is what most slicers need, but it has not been tried in yours. Open it there before a long print.
Is my model uploaded?
No. The repair runs in your browser, which matters for unreleased designs.