CAD Modeling Fusion Skill

Use this skill when a user wants a parametric CAD model, a validated CAD model specification, generated Autodesk Fusion Python code, fallback FreeCAD/OpenSCAD code, or export guidance for STEP/STL/OBJ/F3D workflows.

Do not use this skill for pure mesh sculpting, animation, rendering-only scenes, destructive edits to user CAD files, or executing untrusted generated code without explicit confirmation.

Workflow

1. Parse the request into a ModelSpec JSON object.
2. Ask clarifying questions only when critical dimensions, units, or manufacturing requirements are missing and cannot be inferred.
3. Validate the spec with scripts/validate_spec.py or cad_skill.validators.
4. Choose a backend: fusion first, freecad when Fusion is unavailable, and openscad for simple CSG previews.
5. Generate code with scripts/generate_model.py.
6. Save generated files under outputs/<model_name>/.
7. If execution is requested, run the script in the CAD tool or use the optional Computer Use plan from cad_skill.computer_use_adapter.
8. Report files created, assumptions, validation issues, run instructions, and known limitations.

Safety

• Prefer official scripting APIs over GUI automation.
• Never overwrite, delete, or move user files unless explicitly requested.
• Keep generated scripts in a dedicated output directory.
• Validate units, dimensions, wall thickness, backend feature support, and export requests before generation.
• Treat Computer Use as optional and platform-specific.

Scripts

• Generate code: python scripts/generate_model.py --spec assets/examples/mounting_bracket/example.spec.json --backend fusion --out outputs/mounting_bracket
• Generate all examples: python scripts/generate_all_examples.py --backend all --overwrite
• Validate only: python scripts/validate_spec.py assets/examples/phone_stand/example.spec.json --strict
• Preview plan: python scripts/render_preview.py --spec assets/examples/simple_gear/example.spec.json --backend openscad
• Fusion run plan: python scripts/run_fusion_script.py outputs/mounting_bracket/mounting_bracket_fusion.py

Retrieval Map

Load the narrowest relevant reference first:

• Enclosure-like objects: references/cad_modeling_patterns.md -> Rectangular Enclosure, Lid + Enclosure, Rounded Container, Snap-Fit Enclosure; examples assets/examples/pcb_enclosure/, assets/examples/storage_bin/.
• Brackets, mounts, and fixtures: references/cad_modeling_patterns.md -> Mounting Bracket, Rib Reinforcement, Boss Feature, Camera/Servo Side-Ear Mount; examples assets/examples/mounting_bracket/, assets/examples/servo_mount/, assets/examples/camera_mount/.
• Rotational parts, pulleys, shafts, bearings, and gears: references/cad_modeling_patterns.md -> Gear-Like Wheel, Pulley With Flanges, Bearing Seat, Shaft Adapter, Parametric Knob; examples assets/examples/simple_gear/, assets/examples/pulley/, assets/examples/bearing_mount/, assets/examples/shaft_coupler/.
• Laboratory and scientific fixtures: references/cad_modeling_patterns.md -> Laboratory Rack, Tube Holder, Optical Mount, Lens Retainer Ring, Sample Stage Grid; examples assets/examples/optical_mount/, assets/examples/lens_holder/, assets/examples/sample_stage/, assets/examples/test_tube_rack/, assets/examples/microscope_adapter/.
• Consumer and utility parts: references/cad_modeling_patterns.md -> Phone Stand, Hook, Cable Clip, Storage Tray; examples assets/examples/phone_stand/, assets/examples/cable_clip/, assets/examples/wall_hook/, assets/examples/storage_bin/.
• Fusion API implementation: references/fusion_api_recipes.md; quick overview references/fusion_api_notes.md.
• Manufacturing checks: references/manufacturing_rules.md and references/geometry_validation_rules.md.
• Example selection: assets/examples/README.md and references/examples.md.

References

• references/model_spec_schema.md defines the full ModelSpec format.
• references/cad_modeling_patterns.md is the reusable CAD pattern cookbook.
• references/fusion_api_recipes.md contains Fusion API implementation recipes.
• references/fusion_api_notes.md summarizes Fusion API orientation.
• references/manufacturing_rules.md gives process-specific design rules.
• references/geometry_validation_rules.md defines validation and manufacturability checks.
• references/computer_use_workflow.md covers optional GUI automation.
• references/examples.md explains the bundled example specs.
• references/repository_review.md tracks knowledge-base quality and follow-up recommendations.

The backend generators cover common primitive, boolean, hole, fillet, chamfer, shell, pattern, and export workflows, and emit explicit warnings for unsupported or approximate features.