CadQuery → 3D print workflow

Parametric CAD for the Elegoo Centauri Carbon (256 × 256 × 256 mm build volume).

Describe a part → it gets modelled in CadQuery → reviewed live in CQ-editor → exported print-ready.

Layout

cq                    launcher (build / show / open / list)
parts/                one .py per part; each defines build()
out/                  exports: <name>.step, <name>.3mf, <name>.stl, <name>-preview.png
scripts/build.py      export + preview renderer
.venv/                Python 3.13 virtualenv (do not commit)
requirements.txt      pinned: cadquery 2.8.0, cq-editor 0.7.0

Usage

./cq build smoke_box      # exports STEP + 3MF + STL, renders 4-view preview
./cq show smoke_box       # build + print the preview in-terminal
./cq open parts/foo.py    # open CQ-editor (live 3D, GPU via XWayland)
./cq list                 # list parts

A part file is just:

import cadquery as cq

def build():
    return cq.Workplane("XY").box(60, 40, 20)

# Required — see the CQ-editor note below.
result = build()

build() may return a cq.Workplane, a cq.Assembly, or any CadQuery Shape.

The result = build() line is not optional. CQ-editor only renders module-level CadQuery objects: cq_utils.find_cq_objects() scans the module dict for Workplane / Shape / Assembly / Sketch values. A file that merely defines build() loads without error and shows a completely empty viewport — which looks like the geometry broke, not like a missing line.

The review loop

1. Describe the change.
2. The part file is edited; CQ-editor hot-reloads it (see below) — no restart, no click.
3. Review the viewport. A 4-view PNG grid (ISO/TOP/FRONT/RIGHT) is also rendered into chat so the geometry can be checked, not just the fact that the script ran.
4. Nothing is exported until the shape is approved. ./cq build writes STEP/3MF/STL, so it is the last step, never the first.

Reloading: use File → "Automatic reload and preview". Do not press F5. render() reads editor.get_text_with_eol() — the editor buffer, not the file on disk — so after an external edit F5 re-renders the stale geometry and looks like the change did nothing. "Automatic reload and preview" arms a QFileSystemWatcher; _file_changed() reads the file into the buffer and emits triggerRerender.emit(True), re-rendering ~50 ms after each write. With it enabled, an external edit lands in the viewport on its own. Don't hand-edit in the CQ-editor window while a write is in flight — the reload replaces the whole buffer.

Export formats

• .3mf — feed this to OrcaSlicer. Carries units and colours.
• .step — keep for re-measuring or re-editing the CAD later.
• .stl — universal fallback.

Environment notes (why it looks the way it does)

• Python 3.13, not the system 3.14. cq-editor 0.7.0 declares Requires-Python <=3.14, which in PEP 440 means <=3.14.0 — so the system Python 3.14.8 is rejected outright. The venv uses Fedora's python3.13 package.
• cadquery 2.8.0 has no Model class. Use cq.Workplane / cq.CQ and cq.Assembly. The exporter takes STL, STEP, AMF, SVG, DXF, TJS, VRML, VTP, 3MF, BREP, BIN.
• GPU rendering is preserved. CQ-editor runs on QT_QPA_PLATFORM=xcb (XWayland) so the Intel iGPU does the work. Headless builds use QT_QPA_PLATFORM=offscreen. Avoid forcing llvmpipe/software GL — it makes the viewport unusable on this hardware.
• Preview rendering uses VTK 9.6.2 offscreen. Two gotchas already handled: vtkFeatureEdges emits point scalars that override actor colour (needs ScalarVisibilityOff()), and ResetCamera() fits the bounding sphere, which leaves flat parts tiny in a square tile (replaced with a projected-corner fit_parallel_scale).

Rebuilding the environment

sudo dnf install -y python3.13          # 3.14 is incompatible, see above
python3.13 -m venv .venv
.venv/bin/pip install -r requirements.txt