Build a mounting plate with a through-hole

Level: beginner → intermediate · Workspace: local CAD Editor #/model · Units: millimetres.

This exercise makes a rectangular plate with one circular through-hole, changes the hole size and location, and checks what the resulting native model can—and cannot—certify. It uses the editor's existing Mounting plate with a through-hole example; you do not have to write source programs, topology IDs, or document JSON.

Open the modeling workspace

From a configured Node 22+ repository workspace:

pnpm --filter @barocss/cad-editor build:library
pnpm --filter @barocss/cad-editor-app dev

Open http://127.0.0.1:52010/#/model (or the actual Vite port followed by #/model). The page heading is Model a part. Wait for Accepted model.

1. Open Modeling examples and its Choose an example menu.
2. Select Mounting plate with a through-hole.
3. If an earlier model exists, save anything important, then check Replace accepted model and discard its history and pending dimensions.
4. Choose Load example. Selecting the menu option alone does not replace the model.

Understand the model before editing

The preset starts with an origin-aligned 80 × 40 × 8 mm rectangular plate and a circular through-hole of radius 5 mm, centered at XY [40,20]. Z extrusion runs from 0 to 8 mm. The six numeric drivers correspond to width, depth, height, centerX, centerY, and radius. Here depth means the plate's Y dimension—not the hole's drilling depth.

The authoring chain is rectangle sketch → +Z extrusion → qualified hole. Its two named outputs remain saved:

Output	Meaning	Actual native result
blank	Original uncut rectangular plate	convex-planar; exact certified volume 25,600 mm³
plate	Plate with one stored-rational hole	stored-rational-plate-hole; Certified volume unavailable

Under Visible output body choose plate to inspect the hole, or blank to compare with the intact parent. The preset selects plate on load. Changing visibility does not remove the other saved output, alter dimensions or add an Undo history step. A generic Open chooses the last validated saved output; inspect the selected output name rather than relying on what was visible before saving.

Resize the hole

1. Under Named dimensions, change radius from 5 to 2.5 mm.
2. Before committing, the status Dimension changes pending indicates a draft. The accepted geometry remains unchanged.
3. Select Apply dimensions. Once the status returns to Accepted model, inspect plate in the viewport.
4. Use Undo to restore the original accepted state and Redo to repeat the valid edit. To abandon an unaccepted value, choose Discard draft.

This radius change was measured in the existing native provider fixture. It is not a newly executed browser/GPU demonstration from this documentation change. The screen's sampled opening is only an approximate view of the native boundary.

To move the narrowed hole off-center, try the separate accepted parameter batch centerX: 32.5, centerY: 18.75 (mm), then Apply dimensions. The native provider fixture accepts this combination after the radius-2.5 edit. Treat it as a subsequent edit, not an instruction to change all dimensions before the first acceptance.

Learn to handle an intentional refusal

The stored-rational qualification is intentionally strict. The existing native example records a candidate width:81 after the radius-2.5 edit that refuses with a geometry-qualification cause. This is a bounded provider fixture, not a promise that every integer width behaves similarly or a generic restriction on rectangular plates.

From the accepted off-center state, changing radius to 18.75 reaches the plate boundary and refuses strict containment. A refused Apply dimensions must leave the previous accepted model and saved authored state intact. Review the actual diagnostic, then correct the field or choose Discard draft; do not silently clamp the radius, approximate an intersection, or delete the accepted result.

Save, open, and edit again

Open Save or open a model.

1. Choose Download model to initiate part.cad.json. Verify the browser actually saved it.
2. Choose Choose model file and select the saved file. This stages decoded UTF-8 in Saved model data; file selection is not model acceptance.
3. Review the text. Check Replace accepted model and discard its history and pending dimensions, then select Open saved model.
4. After acceptance, select plate under Visible output body and try another supported radius edit.

The file reader refuses empty files, malformed UTF-8 and content larger than 262,144 bytes. Reading does not replace the model or advance history; native validation only occurs on explicit Open. Saving preserves the authored sketch, extrusion, hole and numeric parameters—not the viewport screenshot or derived triangle mesh.

Native qualification versus display preview

This distinction is essential:

• The plate native output has a qualified stored-rational genus-one boundary, with 7 native faces, 10 vertices, 15 edges, 9 loops and 30 directed edge uses, for one material component. This is a bounded stored-coefficient claim, not unrestricted curved-solid CAD support.
• The separately sampled preview has 256 display vertices and 128 triangles; display counts must not be mistaken for native B-Rep topology.
• Its preview retains solid:false and topologyCertified:false. Those flags concern the derived mesh; they do not undo the separately qualified native boundary.
• Certified volume unavailable for plate is neither zero nor empty. The exact 25,600 mm³ belongs to blank, before cutting the hole. No certified ideal-cylinder subtraction or manufacturing/mass claim follows.
• Approximate viewport face picking is not exact persistent topology identity, manufacturing certification, or a material-classification proof.

The authoritative details and the executable public TypeScript sample remain in Mounting plate with a through-hole.

Evidence status

Source-backed here: preset name, dimensions and named outputs, native provider receipt, accepted parameter edits/refusals, current UI controls, stage-before-Open semantics, and qualified versus sampled geometry distinctions.

Not rerun in this documentation-only change: actual browser interaction, rendered GPU pixels, screenshots, OS file dialog, physical download and fresh Open, VitePress production build. These gates remain UNRUN until separately executed and recorded. No synthetic screenshot is evidence.

First model: underside pocket · Round post · CAD Editor overview · Advanced modeling API