cadSet/text-to-cad/skills/cad/SKILL.md

name, description

name	description
cad	Create, modify, inspect, and validate STEP-first parametric CAD parts and assemblies. Use for natural-language CAD specs, reference images, 2D technical drawings, STEP/STP generation or direct inspection, Python CAD source, source-level joints, selector references, geometry facts, measurements, mating deltas, snapshots, and secondary STL/3MF/native GLB outputs from CAD geometry.

CAD generation, inspection, and validation

Provenance: maintained in earthtojake/text-to-cad. Use the installed local skill files as the runtime source of truth; the repository link is only for provenance and release review.

Purpose

Create or modify parametric CAD models from natural-language requirements, generate validated STEP/STP artifacts, inspect geometry references, and return checked outputs. Treat STEP as the primary CAD artifact. Treat STL, 3MF, and native GLB as secondary export workflows that branch from a STEP-first process. For assemblies, prefer cadpy.assembly.AssemblyHelper with source-level build123d joints, named mating datums, and native labels when the parts have functional assembly relationships.

There are two ways into the STEP workflow: generate from build123d Python source (the default when designing from scratch or modifying a generated model), or import an existing STEP/STP file directly (when no generator exists or the user explicitly targets the STEP file). Both produce the same inspectable artifacts.

Use this skill when

Use this skill when the user asks for CAD files, STEP/STP files, build123d source, selector refs such as #o1.2.f1, mechanical parts, assemblies, enclosures, brackets, fixtures, holes, counterbores, countersinks, slots, pockets, bosses, standoffs, ribs, fillets, chamfers, shells, source-level joints, mating, or measurements. Also use it when the user supplies reference images or 2D technical drawings of a part to reproduce or take design intent from.

Also use it when the user asks for STL, 3MF, or native GLB output from CAD geometry. Keep those workflows secondary and load supported-exports.md for details. For 2D DXF drawings, use the $dxf skill; when a DXF projects from a 3D part, this skill owns the STEP geometry and $dxf owns the drawing.

Do not use this skill for render-only concept art, CAM toolpaths, engineering certification, FEA conclusions, architectural BIM, or freehand illustration unless the user also needs CAD geometry.

Default assumptions

Use these defaults unless the user specifies otherwise. These are first-pass modeling defaults, not manufacturability, tolerance, or certification claims:

• Units: millimeters.
• Origin: per the part-type defaults in references/positioning.md; center of the main part or assembly when nothing better applies.
• Base plane: XY.
• Up/extrusion axis: positive Z.
• Output geometry: closed, positive-volume solids unless the user requests surfaces or construction geometry.
• STEP structure: one valid solid, a compound of solids, or a labeled assembly compound.
• Assembly structure: fixed root part, part-local frames, named mating datums, AssemblyHelper relationships backed by build123d joints where applicable, explicit generated placements, and verbose native labels.
• Small plastic enclosure wall: 2.0-3.0 mm when unspecified.
• Cosmetic fillet: 1.0-3.0 mm when safe for local geometry.
• M3/M4/M5 normal clearance holes: 3.4/4.5/5.5 mm unless another standard is requested.

Ask one focused clarification question only when missing information makes the model impossible, fit-critical, safety-critical, or compliance-bound. Otherwise proceed with explicit assumptions.

Tools and paths

From the CAD skill directory, the launcher shape is:

python scripts/step ...      # STEP generation, GLB/topology artifacts, mesh sidecars
python scripts/inspect ...   # refs, measure, align, frame, diff
python scripts/snapshot ...  # PNG/GIF visual review packets

Use the active project Python interpreter; treat python in examples as an interpreter placeholder. Use python scripts/<tool> --help for the complete current command interface; reference docs show recommended workflows, not every flag.

Target paths resolve from the command's current working directory, not from the skill directory. Run commands from the workspace that owns the artifacts and pass cwd-relative target paths so project CAD files never resolve accidentally under the skill directory. Keep a STEP output and its Python generator in the same directory with the same basename unless the user explicitly requests otherwise.

CAD references are #... selector tokens local to a target, for example #o1.2 or #o1.2.f1. Pass the STEP/CAD file as a separate target argument when using CAD CLIs.

Required workflow

Scale depth to the task: a simple part needs a short brief and few spec-driven checks; assemblies and fit-critical work need full positioning and alignment validation.

1. Classify the task. New part, new assembly, source modification, direct STEP/STP inspection, reference selection, measurement/alignment check, snapshot review, or secondary output request.
2. Load only the needed references. Use the triggers below instead of reading the whole reference set.
3. Write a natural-language CAD brief. Extract dimensions, units, coordinate convention, feature intent, output paths, assumptions, and validation targets from all provided inputs — prose, reference images, technical drawings. Use references/cad-brief.md.
4. Check named purchasable components. When an assembly includes named off-the-shelf actuators, servos, motors, electronics boards, connectors, or other purchasable components, search $step-parts before creating simplified placeholder geometry. If no exact match is found, record the miss and then use a documented envelope.
5. Plan before coding. Define parameters, intent labels, source paths, expected bounding boxes, and any mating/positioning datums before editing.
6. Edit source, not generated artifacts. Author build123d Python with gen_step(). When a Python generator exists, run scripts/step on the generator, never on its exported STEP. Use direct STEP/STP targets (--kind part|assembly) only for imports with no generator or when the user explicitly identifies the STEP/STP file as the target.
7. Generate explicit targets. Run scripts/step on explicit targets only; do not run directory-wide generation.
8. Validate geometrically. Run scripts/inspect refs <step-or-cad-target> --facts --planes --positioning as the baseline, then verify the dimensions and relationships the user's spec calls out with targeted measure, align, frame, or diff checks.
9. Snapshot the primary STEP — snapshot validation is mandatory. After creating or visibly updating a primary STEP/STP part or assembly, ALWAYS run CAD scripts/snapshot against it and review the output; deterministic checks passing is not a reason to skip. The only skip cases are documented in references/snapshot-review.md (no visible geometry changed, or no valid artifact exists); report the reason when skipping.
10. Repair and rerun. If a check fails, change the smallest responsible source section, regenerate, and rerun the failed validation.

Handoff

After completing CAD work that creates or modifies .step, .stp, .stl, .3mf, or native .glb artifacts, you must ALWAYS hand the explicit file path(s) to $cad-viewer when that skill is installed. $cad-viewer must start CAD Viewer if it is not already running and return link(s) to the relevant created or updated file(s); include those live viewer link(s) in the final response. If $cad-viewer is unavailable or startup fails, report that and rely on CLI inspection plus snapshots instead of silently omitting the handoff. This rule applies to every workflow in this skill, including secondary STL/3MF/GLB outputs.

When verification snapshots are generated, include the saved PNG/GIF snapshot(s) in the final response. If no snapshot applies, or if snapshot generation fails, say why and report the deterministic validation that still ran.

Non-negotiables

• Keep STEP as the primary validated CAD artifact. Generated STEP/STP, STL, 3MF, GLB/topology outputs, and render sidecars are derived artifacts; STL/3MF are secondary unless the user explicitly says otherwise.
• Use named parameters, closed solids, verbose native build123d labels, and source-controlled geometry intent.
• Author assembly positioning in source. references/positioning.md is authoritative for AssemblyHelper, build123d joints, explicit Location transforms, and alignment validation.
• Do not use git status, git diff, or file-size churn as CAD comparison for large exported STEP/STP, GLB/topology, STL, or 3MF artifacts. Compare source changes, scripts/inspect summaries, snapshots, or generated topology output instead; use path-limited git status only for bookkeeping.
• Report only checks that actually ran or are directly supported by tool output.

Progressive references

Load these files only when their trigger applies:

• references/cad-brief.md — converting prose, reference images, and technical drawings into a CAD brief.
• references/build123d-modeling.md — build123d modeling patterns, topology, selectors, features, labels.
• references/step-generation.md — STEP generation from Python source, direct STEP/STP imports, and post-generation steps.
• references/inspection-and-validation.md — validation sequence, selector refs, facts, planes, measurements, alignment, diff, frame, and validation reporting.
• references/snapshot-review.md — mandatory snapshot policy, packet sizing, targeted views, and converting visual findings into geometry checks.
• references/positioning.md — part-local datums and origins, assembly transforms, build123d joints, CLI alignment validation, and positioning reports.
• references/parameters.md — parameterizing or animating a STEP model: source parameters, .step.js sidecar modules, viewer controls, and animation design.
• references/supported-exports.md — secondary STL/3MF/native GLB sidecar workflows.
• references/repair-loop.md — diagnosis and repair procedures.
• references/part-families/bearing-housing.md — bearing housings and seats: bearing housing, bearing seat, bearing support, pillow block, flanged bearing housing, cartridge bearing holder, 轴承座, 轴承支座, 带座轴承.
• references/part-families/cup.md — drinking vessels and mugs: cup, mug, water cup, tumbler, handled cup, travel mug, 水杯, 杯子, 马克杯, 茶杯.

• Pack: skill-pack-curated-20260807

Use CAD-SkillX references only after the core build123d references are loaded. For a matching request, read one Planning skill first, then add only the Functional and Atomic skills required by the requested geometry. Do not read the whole pack by default.

Planning skills:

• references/cad-skillx/planning/bearing-housing-or-seat.planning.md — bearing housing, bearing seat, bearing block, bushing seat, pillow block, 轴承座, 轴承支座, 带座轴承.
• references/cad-skillx/planning/flange.planning.md — flange, circular flange, pipe flange, coupling flange, flanged sleeve, 法兰, 法兰盘.
• references/cad-skillx/planning/hexagonal-nut.planning.md — hex nut, hexagonal nut, threaded nut, internal threaded bore, 六角螺母, 螺母.
• references/cad-skillx/planning/mounting-bracket.planning.md — mounting bracket, support bracket, L/U/T bracket, bracket with holes, web/lug/tab/boss, 安装支架, 支架.
• references/cad-skillx/planning/mounting-plate.planning.md — mounting plate, base plate, adapter plate, fixture plate, flat plate with holes, 安装板, 安装底板, 安装版.
• references/cad-skillx/planning/simple-shaft-or-cylindrical-rod.planning.md — simple shaft, cylindrical rod, pin, standoff, stepped shaft, end hole, 轴, 阶梯轴, 圆柱杆, 销轴.

Functional skills:

• references/cad-skillx/functional/axisymmetric-revolve-strategy.functional.md — read for axisymmetric/turned bodies, stepped shafts, bushings, washers, sleeves, flange hubs, grooves, or revolved cuts.
• references/cad-skillx/functional/bearing-bore-seat.functional.md — read with bearing housing/seat requests where a shaft clearance bore, bearing pocket, shoulder, or seat depth is required.
• references/cad-skillx/functional/flange-bolt-circle.functional.md — read with flange requests containing bolt circle, pitch circle, PCD, circular bolt pattern, or evenly spaced flange holes.
• references/cad-skillx/functional/mounting-plate-hole-layout.functional.md — read with mounting/base/adapter plates containing rectangular hole grids, edge margins, slots, threaded holes, counterbores, or countersinks.
• references/cad-skillx/functional/slotted-adjustment-feature.functional.md — read when the model needs slots, slotted holes, elongated holes, guide slots, or adjustment slots.
• references/cad-skillx/functional/standard-hole-wizard.functional.md — read whenever standard clearance holes, threaded/tapped holes, counterbores, countersinks, dowel holes, or screw-seat holes are required.
• references/cad-skillx/functional/symmetric-feature-layout.functional.md — read when holes, bosses, tabs, slots, cutouts, or ribs are mirrored, centered, or symmetric about a centerline/midplane.

Atomic skills:

• references/cad-skillx/atomic/coaxial-bore-rule.atomic.md — read when bore, pocket, hub, sleeve, bearing seat, shaft clearance, pilot diameter, or counterbore must share one axis.
• references/cad-skillx/atomic/counterbored-hole-creation.atomic.md — read for counterbored holes, socket head/cap screw seats, flush screw-head recesses.
• references/cad-skillx/atomic/extrude-base-profile.atomic.md — read when the base body is an extruded rectangle, circle, annulus, hexagon, block, plate blank, bracket base, or simple cylinder.
• references/cad-skillx/atomic/fillet-chamfer-last.atomic.md — read when finishing edges with chamfers, fillets, deburring, lead-ins, or stress-relief rounds.
• references/cad-skillx/atomic/pattern-holes-from-datum.atomic.md — read for repeated holes controlled by pitch, angle, symmetry, linear pattern, circular pattern, mirror pattern, or bolt pattern.
• references/cad-skillx/atomic/revolve-profile-around-axis.atomic.md — read for individual revolve/revolved-cut operations around a construction axis.
• references/cad-skillx/atomic/threaded-hole-creation.atomic.md — read for internal threaded/tapped holes such as M3/M4/M5/M6/M8/M10.
• references/cad-skillx/atomic/through-hole-cut.atomic.md — read for plain through holes, clearance holes, central holes, circular openings, or bore-through cuts.

Recommended CAD-SkillX combinations:

• Bearing housing / 轴承座: planning bearing housing + functional bearing bore seat + atomic coaxial bore; add standard hole wizard, pattern holes, counterbore/threaded/through-hole, and fillet-chamfer-last only if those features are requested.
• Flange / 法兰: planning flange + functional flange bolt circle + atomic coaxial bore + pattern holes from datum; add axisymmetric revolve when the flange has a hub, sleeve, steps, grooves, or turned profile.
• Mounting plate / 安装板: planning mounting plate + functional mounting plate hole layout; add standard hole wizard, symmetric feature layout, slots, pattern holes, counterbored/threaded/through holes, and fillet-chamfer-last as needed.
• Mounting bracket / 安装支架: planning mounting bracket; add standard hole wizard, symmetric feature layout, slotted adjustment, extrude base profile, pattern holes, and fillet-chamfer-last as needed.
• Simple shaft / cylindrical rod / 轴: planning simple shaft or cylindrical rod; add axisymmetric revolve or revolve-profile-around-axis for steps/shoulders/grooves, threaded-hole creation for centered end holes, and fillet-chamfer-last for end edge breaks.
• Hexagonal nut / 六角螺母: planning hexagonal nut + atomic threaded-hole creation + fillet-chamfer-last; add revolve-profile-around-axis only when using a revolved blank or revolved thread/counterbore.

Final responses should include generated files, returned $cad-viewer viewer links, verification snapshots, validation actually run, assumptions, and caveats. Use references/inspection-and-validation.md for report structure.