engineering-drawing

Engineering drawing

Provenance: maintained in earthtojake/text-to-cad. Use the installed local skill files as the runtime source of truth.

An engineering drawing is a DOCUMENT derived from a part. cadgen.eng_drawing projects views from the part's geometry, places dimensions between points ON that geometry, finds centre marks on it, and lays the result out on an ISO sheet with a frame and a title block. Change the model, rerun the drawing script, and the views, hidden lines and measured values move with it. Nothing on the sheet is drawn by hand, and nothing on it is a number you typed unless you chose to override a value.

The output is one PDF. That is what a shop receives and what every operating system opens. No DXF is written, nothing is paired or linked, and there is no CLI: the script is the interface. $dxf makes cut layouts and flat patterns, which are toolpaths, not documents; the two are different jobs.

Setup

Run cadgen through uv, so this skill's commands share one installation, and its warm build daemon, with the CAD app's server:

• cadgen below means uvx --no-config --managed-python --python 3.13 --from cadgen==0.7.21 cadgen
• python below means uvx --no-config --managed-python --python 3.13 --from cadgen==0.7.21 python

The first run downloads that installation; later runs reuse it.

Workflow

1. Get the part. cadgen.read_step(Path(__file__).parent / "../STEP/part.step") reads the artifact a @step model wrote (run python <model>.py first); a live build123d shape works just as well. The drawing documents geometry, it does not build it.
2. Write <name>_drawing.py beside the model, from the template. Import the model facts the dimensions reference (hole pitch, overall size, wall) from the model module rather than retyping them, so moving a feature moves its dimension.
3. Place views with sheet.three_views(part, iso=True), which returns FOUR views: top, front and right in third angle with room for two rows of dimensions, plus an isometric in the free corner. sheet.three_views(part) returns three. Use sheet.view(part, name, at=(x, y)) (sheet millimetres from the bottom-left corner; A3 is 420 × 297, A4 is 297 × 210) only for a custom layout.
4. Dimension what a maker needs, in MODEL coordinates: overall size per view (view.overall()), feature positions and sizes (view.dim, with tol= or fit= where the design requires one), holes as callouts (view.hole: thru, depth, counterbore, countersink, thread), and notes with leaders (view.note). Leave text unset so the dimension is measured; give a value only where the model does not define it. Leave offset unset too and the dimension takes the next free row outside the view; pass one only to place a dimension deliberately, and remember it is measured from the dimension's own points, not the view's edge. Keep notes few and short; one wider than the sheet's note column is refused, and notes= takes a LIST (notes="BREAK EDGES" is a sequence of eleven characters, so it is refused too).
5. Run python <name>_drawing.py. It prints the PDF it wrote, and anything it noticed while drawing — read those first:
   • "measures blank paper": the dimension's model points do not land on the view's geometry. Almost always the part was built from a corner and the script assumed it was centred. Check the part's bounding box.
   • "annotation overlaps": two callouts print on top of each other, usually one view's outermost dimension against the label of the view above it. Pass a bigger three_views(gap=...) or place one with offset=. The text is measured as the renderer draws it, glyph by glyph, so this fires on ink and not on markup: a chain of toleranced dimensions is silent when the values clear each other.