Build an editable design that the user can tune after the first print. Preserve the user's chosen workflow: if they request Computer Use, operate Fusion through the available Computer Use tools. This skill supplies guidance, not a Fusion connection or permission to change unrelated projects.
Establish the design intent
- Inspect the open document, active component, units, timeline position, existing geometry, and saved state before editing. Preserve existing work.
- For measurements from videos, notes, or photos, record the final corrected values with their reference surfaces. Distinguish inside/outside diameter, radius, radial width, depth, and available height. Mark earlier values as superseded; keep assumptions separate. Speech and visible measurements must be reconciled before choosing geometry.
- Identify retained parts, mating surfaces, insertion/removal paths, and the intended print material. Ask only about missing information that changes the design; proceed with clearly labeled, reversible assumptions elsewhere.
- For more than one physical part, create and name a component for each part before its geometry, then activate it before sketching. Use an assembly-capable design type when required by the installed Fusion version. A single part may contain multiple construction bodies; do not automatically turn every body into a separate component.
Parameterize before building
Make every dimension the user may tune a named parameter: measured envelope, fit clearance, wall/base thickness, feature size, spacing/count, and finishing radii. Use meaningful names, units, and comments describing the reference and purpose. Use expressions for dependent dimensions instead of repeating their evaluated numbers.
Keep measurements and manufacturing allowances independent. For a circular insert, for example:
outer_d = housing_inside_d - 2 * radial_clearance
inner_d = outer_d - 2 * band_width
total_height = available_height - top_clearance
Define these parameters from the actual design; the example supplies relationships, not default dimensions. Use dimensionless integers for counts. Do not build circular dependencies or create a separate user parameter for an incidental origin coordinate already constrained geometrically. Ordinary user parameters are sufficient; a paid Configuration Table is not required just to make dimensions editable.
Read modeling-and-printing.md for fits, patterns, fillet selection, or print preparation.
Build an inspectable feature history
- Save a named document early, once minimal useful geometry exists. Keep parametric history enabled for new editable designs; inspect the consequences before changing the modeling mode of an existing document.
- Anchor sketches to the intended origin/reference geometry. Constrain position and shape, then dimension using parameter names. Prefer stable origin planes, axes, and deliberate construction geometry over faces likely to disappear after an edit.
- Create the main solid, then functional cuts, holes, and joins. Check profile selection, operation type, direction, extent, and target body. A correct-looking preview can still create an unintended extra body.
- For repeated details, create and verify one seed feature, then pattern the feature around a stable axis or direction. Drive count and spacing from design intent. Inspect the seed and the closure between the first and last instances.
- Add small finishing fillets near the end, after the main geometry and patterns are stable. Use named radii such as
edge_radius; keep a distinctroot_radiusorbase_edge_radiuswhen it serves a different purpose. A functional or structural fillet may belong earlier when later features depend on it. - Save after meaningful feature groups and before fragile edits. Prefer a saved, useful intermediate model to a long unsaved session.
Do not round every edge indiscriminately. Preserve mating faces, necessary sharp features, adequate wall thickness, and the intended bed-contact footprint. Inspect slot roots, tips, narrow gaps, and underside overhangs after rounding.
Verify before handing over
- Confirm the intended solid bodies/components exist, no unexpected bodies remain, and the timeline computes without unresolved errors. Inspect critical dimensions and clearances in the resulting geometry.
- Check the actual sketch/feature expressions, including pattern quantity and fillet radius. A parameter in the table is not proof that the feature uses it.
- When editability is central, save a baseline and test a modest change to a meaningful driving parameter. Check the affected features, restore the intended value, recompute, and verify the restored value before the final save/export. Test changed pattern topology when variable counts are part of the requirement.
- Check assembly/removal travel and cleaning access when relevant. Mark untested physical fit or print performance as provisional; CAD success does not establish either.
- Preserve a native editable archive, normally F3D for a self-contained design; use the appropriate native assembly export for linked designs. Supply a print mesh only when requested or useful for the agreed handoff. A mesh is not a substitute for parameter/history preservation.
- Verify export completion and file existence. File integrity, CAD geometry, slicer output, and physical fit are separate checks; report only those actually performed.
Finish with the saved design/version, the main tuning parameters, a link to the exported deliverable, and any material unresolved fit issue. Keep the model visible when practical.
When operating Fusion through Computer Use
Read computer-use.md before a substantial UI session or when a dialog stops behaving as expected. It covers timeline rollback, HUD focus, expression entry, save checkpoints, and bounded recovery. Follow the current tool's documented API; never reuse another session's pixel coordinates, accessibility indices, or installation paths.