Split models for easier 3D printing
A model may be too large for your print bed, have an awkward seam, or need separate pieces for different filament colors. Drop one STL or 3MF onto the sidebar or viewer, or use the upload button. The workspace highlights when a file is ready to drop. Resize the sidebar to give the model more room.
Dropping a new file replaces the current model and cancels any operation on it. This also works while editing color regions, so finish or download your current work before opening a different file. Drop one file at a time; the same file-type, size and mesh checks apply as with the upload button.
Create regions with edge fill
Click Create color regions, then click an area of the model. The yellow preview spreads across triangles that share an edge. It stops when the angle between neighboring faces is greater than Edge angle.
A low angle keeps the selection on flatter surfaces. A higher angle reaches around sharper corners. Smooth curves can fill all the way around, because each neighboring triangle may turn only a little. The tool follows the mesh; it does not recognize eyes, clothes, or other named parts.
Adjust the angle to update your current selection. Choose New region color or an existing region, then click Apply region. Repeat for other areas. Undo region reverses up to ten recent changes. Use regions in splitter applies the edited model and starts a fresh split. Back without applying leaves the source model as it was.
Coloring a surface and making a solid part are different steps. Color extraction uses the existing experimental cap method. Newly created flat patches are refused during extraction because they have no printable thickness. A region that wraps around part of the model may be extracted, but complex boundaries may need repair. Use the output preview and your slicer to inspect each piece.
Split a 3MF by its existing colors or objects
Painted 3MF files from Bambu Studio or OrcaSlicer may already contain the regions you need. Choose Color regions, select areas in the viewer or list, and click Split selected. Selected regions become separate 3MF files, with a remaining body when geometry is left over.
Choose Objects to export the object resources inside a package. Build plate items separates items listed in the file's build section. These options depend on the structure that the original program saved. Different slicers store color and assembly data differently, so not every package will expose the same choices.
Cut an STL or 3MF with a plane
For a straight split, choose Manual cut. Select the X, Y, or Z axis, move Position, and adjust Tilt A or Tilt B if the seam should slope. Choose which side stays active, then make the cut.
The removed piece stays in the output list. You can cut the remaining body again without starting over. Choose None, Cylinder, or Square for the connector method. Connector size, socket tolerance, and connector side control the joint where the cut supports one. Inspect the joint before printing and test the fit with your filament.
What your file keeps
STL holds a triangle mesh and usually has no usable color information or unit setting. This tool treats STL coordinates as millimeters. Adding regions creates color labels in a 3MF working package; it cannot recover colors absent from the original file.
3MF can hold meshes, colors, multiple objects, units, and slicer-specific settings. Ordinary object and build-item splitting uses the source package. Applying newly edited regions rebuilds the visible geometry as one object, so original object structure, textures, and slicer settings are not retained. Your original file on disk stays unchanged.
Outputs are 3MF files. Use Download combined to collect the resulting pieces in one package. If you need a plain mesh afterward, use the Free 3MF to STL Converter.
File size and common problems
Files are read and processed in your browser, with no account or model upload to a server. The upload limit is 100 MB. STL import and region editing support up to 500,000 triangles, and the editor supports up to 16 colors. Models with more than 512 separate preview regions are refused to keep the workspace responsive. Available memory still matters, especially for compressed 3MF projects that expand into large meshes.
Disconnected surfaces, open edges, and edges shared by more than two triangles stop a fill. Small gaps or mismatched vertices can also keep a selection from spreading. Reducing mesh detail in your modeling program may help with large files, but inspect the shape afterward.
Check scale, closed surfaces, and wall thickness in your slicer before printing. The splitter does not repair every broken mesh or guarantee that every colored region becomes a printable solid. For a separate mesh inspection, open the Free STL Viewer. For simple single-material models, the Free STL to Gcode Converter can help with the next step.