For Bambu Studio, OrcaSlicer and any slicer that reads 3MF
STL to 3MF Converter, Free, One Part per File
Drop one STL to get a 3MF with the same mesh, centered on the plate. Drop several, like a model shared as one STL per color, and they become one object with one part per file, numbered in your order: Bambu Studio and OrcaSlicer put part 1 on filament 1, part 2 on filament 2. It runs in your browser: nothing is uploaded and nothing is charged.
What the Converter Does With Your STL Files
- 1Reads binary and ASCII STL, including binary files whose header starts with the word solid.
- 2Welds the corners that an STL repeats in every triangle, so the 3MF stores each vertex once, and leaves out zero-area triangles, which the 3MF format does not allow. It counts them.
- 3Converts centimeters or inches to millimeters when you say the STL was not drawn in mm.
- 4Puts the model on the plate: centered, resting at z = 0. Several files keep their positions relative to each other, which is what keeps the colors of a multicolor model lined up.
- 5With several files, writes one object with one part per file, named after the file, and gives part 1 filament 1, part 2 filament 2, in the order of your list.
- 6Checks every part: triangle count, size in mm and whether it is watertight. Nothing is repaired or simplified.
Before You Convert Several STL Files
Three things decide how the parts land in your slicer.
Files that belong together
Load the colors of one model in the same batch. They must come from the same export so they share coordinates: the converter keeps their positions exactly, it does not move one part against another.
List order is filament order
The first file is part 1 on filament 1, the second is part 2 on filament 2. Use the arrows to reorder the list before converting.
Enough filaments in the project
Bambu Studio puts a part whose number is above the filament count of the project on filament 1, without a warning. Sync your AMS, or add filaments until you have one per part.
Why a 3MF Instead of Several STL Files?
Several STL files load as several objects unless you tell the slicer to keep them together, and each one gets its filament by hand. In this 3MF they arrive as one object, the parts in place and numbered by filament. A 3MF also states its unit, millimeters, so it cannot be misread in inches, and it stores each vertex once in a compressed package: on sample models of 2,000 to 30,000 triangles, the 3MF came out 4 to 6 times smaller than the STL.
STL to 3MF Questions
Is the STL to 3MF converter really free?
Yes. The 3MF is written in your browser from the STL files you already have: no account, no watermark, no limit. What VectoSolve charges for is turning a picture (PNG, JPG) into a clean vector.
Are my STL files uploaded anywhere?
No. They are read and converted in your browser tab. Close the page and they are gone.
How do I turn several STL files into one multicolor 3MF?
Drop all the files at once, one per color, put them in filament order with the arrows, then convert. You get one object with one part per file: part 1 on filament 1, part 2 on filament 2. Sync your AMS (or add filaments until you have one per part) and give each slot its color.
Bambu Studio says the file loads geometry data only. Is something wrong?
No. With several files, the 3MF carries the parts and their filament numbers but no printer profile, on purpose: writing one would replace your own printer settings. Click OK and every part keeps its number.
My STL was made in inches. What do I choose?
Choose Inches (or Centimeters) under Units of the STL before converting. An STL has no unit and slicers read it in millimeters; the 3MF is written in millimeters at the right size.
Will the 3MF be smaller than my STL?
For a real model, yes. An STL repeats each corner in every triangle; a 3MF stores it once and compresses the package. On sample models of 2,000 to 30,000 triangles, the 3MF was 4 to 6 times smaller. Only a tiny file of a few triangles comes out larger, because of the package itself. The tool shows both sizes after converting.
Does the converter repair my STL?
No. It welds duplicate corners and leaves out zero-area triangles, then checks each part and tells you if it is watertight. Holes and flipped faces stay as they are: repair them in your slicer or modeling app.
Can I convert a 3MF back to STL?
Yes, with the free 3MF to STL converter, which also splits a project into one STL per object or per part.
Turn your STL files into a 3MF now
Free, in your browser, no signup.
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