STL Inspector CLI

A small Python CLI for inspecting STL files and printing useful geometry metadata without needing a slicer open.

What It Does

• detects ASCII vs binary STL
• counts triangles
• computes bounding box and dimensions
• computes surface area
• reports centroid and min/max corners
• prints either JSON or a terminal table

This is meant for quick validation when you want answers like:

• "Did this export come out the right size?"
• "Which part is bigger than I thought?"
• "Did I just generate a weirdly tiny coupon by mistake?"

Install

python -m pip install -e .

Run Tests

python -m unittest discover -s tests
python -m build

See It Work

The CLI is designed to be copied into a print-review workflow:

stl-inspector part_a.stl --format json --pretty

It reports the file type, triangle count, dimensions, surface area, and centroid without opening a slicer. The committed sample reports are representative output from the same geometry-report shape used by the CLI.

Usage

stl-inspector part_a.stl
stl-inspector part_a.stl part_b.stl --format json
stl-inspector part_a.stl --pretty

Example Output

{
  "file_name": "bench_mechanism_v3_base.stl",
  "stl_type": "ascii",
  "triangle_count": 820,
  "dimensions_mm": {
    "x": 92.0,
    "y": 38.0,
    "z": 22.0
  }
}

Full sample reports:

• sample_reports/bench_mechanism_v3_base.json
• sample_reports/bench_mechanism_v3_carriage.json
• sample_reports/bench_mechanism_v3_m3_test_block.json

Why I Built It

I wanted something faster and scriptable than bouncing between OpenSCAD and a slicer every time I needed basic geometry facts.

Repo Layout

stl-inspector-cli/
├── README.md
├── pyproject.toml
├── src/stl_inspector/
│   ├── __init__.py
│   ├── cli.py
│   └── parser.py
├── sample_reports/
│   ├── bench_mechanism_v3_base.json
│   ├── bench_mechanism_v3_carriage.json
│   └── bench_mechanism_v3_m3_test_block.json
├── tests/
│   └── test_parser.py

Current Limitations

• Units are reported as millimeters by convention; STL does not carry units.
• The CLI focuses on geometry summary data, not mesh repair.
• Extremely large files are rejected on purpose instead of being streamed loosely.