stl-tools

A small Python library + CLI for the common pre-slice tasks every 3D-print hobbyist hits: checking whether a mesh is manifold (watertight), repairing it if it isn't, adding a flat base so the model sits on the build plate, and normalizing units so the slicer interprets dimensions correctly.

Works on any STL (or any other format trimesh can read). Designed initially to post-process exports from the Ritn3D floor-plan- to-3D-model pipeline before sending them to Cura, PrusaSlicer, Bambu Studio, or Lychee — but the library has no dependency on Ritn3D and is useful for any mesh-prep workflow.

Install

pip install stl-tools

CLI

# Inspect a mesh
stl-tools info mymodel.stl

# Repair a non-manifold mesh in place
stl-tools repair broken.stl -o fixed.stl

# Add a 2mm flat base
stl-tools add-base mymodel.stl -o with_base.stl --thickness 2.0

# Scale from meters to millimeters (Blender default → slicer default)
stl-tools scale meters.stl -o mm.stl --factor 1000.0

Library

from stl_tools import (
    load_mesh, save_mesh,
    is_manifold, repair_mesh,
    add_flat_base, set_scale, bbox_info,
)

mesh = load_mesh("input.stl")

if not is_manifold(mesh):
    mesh = repair_mesh(mesh)

# Architectural model: meters → mm, then flat base for the build plate
set_scale(mesh, 1000.0)
mesh = add_flat_base(mesh, thickness_mm=2.0)

print(bbox_info(mesh))
# {'min': (...), 'max': (...), 'size': (...), 'center': (...), 'volume_mm3': ...}

save_mesh(mesh, "ready_to_slice.stl")

What's in scope

What's out of scope

This library is intentionally small. For heavier operations — mesh decimation, remeshing, support generation, slicing itself — use the right tool for the job:

• trimesh itself (this lib wraps it) for richer mesh ops
• PyMeshLab for advanced repair, remeshing, decimation
• Cura / PrusaSlicer / Bambu Studio for actual slicing and supports
• Blender's 3D-Print toolbox for interactive repair on severely broken meshes

Why this exists

Every hobbyist who exports a 3D model from Blender, SketchUp, an AI tool, or a custom pipeline ends up writing the same five-line trimesh snippet to make the file slicer-ready. We did too — and after the tenth copy-paste, we wrote it down as a library.

If you're using Ritn3D's STL export (Pro+ tier) and want to apply additional post-processing before slicing — different base thickness, different units, extra repair — pip-install this, run two CLI commands, and you're done.

Compatibility

• Python 3.9+
• Tested on Linux, macOS, Windows
• STL is the primary target; OBJ, PLY, GLB also work where trimesh supports them

License

MIT — see LICENSE.

Acknowledgements

Built on top of trimesh, the standard Python mesh library. If you find this useful, star trimesh too — the heavy lifting happens there.

Maintained by

Ritn3D — an AI floor-plan-to-3D-model tool. We needed slicer-ready STL output for the Pro+ tier, wrote this to do it, and open-sourced it for everyone else doing the same thing.