Sheet Metal Corner Fillet

Status: Implemented (Rust-kernel-backed)

Sheet Metal Corner Fillet breaks a sharp outline corner of a sheet-metal plate with a circular arc tangent to both adjacent outline segments — the "break corner" treatment a sheet part needs, not an edge blend.

It is not the general Fillet, which blends the edges of a solid. This feature edits the plate's outline, so the rounded corner appears both in the folded solid and in the flat pattern.

Inputs

• sheet – single reference_selection (SOLID, default null). The target sheet-metal body; optional when the document contains exactly one sheet-metal body.
• corners – multiple reference_selection (FACE or EDGE, default null). These picks mix freely in one feature:
  • a corner edge — the vertical thickness edge between two plate side faces. One pick, one corner.
  • a plate top or bottom face — expands to every treatable corner of that plate.
  • the two adjacent side faces of a corner, so selecting all four side faces of a rectangular tab treats all four corners.
• radius – number, default 1. The corner fillet radius.
• id – string, default null. Optional identifier for the history entry.

Behaviour

• Picks that name the same corner treat it once.
• When two corners share an outline segment, the second setback is checked against the already shortened segment, so corners on one segment can never cross.
• The body is rebuilt in place, keeping its name.
• A face pick treats each corner that can be treated: untreatable vertices on that plate are skipped silently rather than failing the feature.

Limitations

These are refused rather than misbuilt:

• Convex, single-flat corners only. A concave / reflex corner — one where the outline turns right on the counter-clockwise loop — is refused.
• Both adjacent segments must be straight and carry no bend. A corner whose segment is curved, or lies on a fold line shared with another flat, is refused.
• The fillet's tangent setback — the radius divided by the tangent of half the corner's interior angle, which is the radius itself at a 90° corner — must be strictly shorter than both current adjacent segments. An oversize radius is refused rather than producing a self-intersecting outline.
• radius must be positive.
• A corners selection is required; there is no "all corners of the body" default. A plate face pick with no treatable corner is an error naming that plate.
• A sheet target that is not a sheet-metal body is an error. With no sheet given and zero or several sheet-metal bodies present, the feature passes through without doing anything — select the body explicitly.

Related

• Sheet Metal Corner Chamfer — the straight-bevel sibling with an identical selection model.
• Sheet Metal Tab — seeds the tree these corners live in.

Where to find it

Offered in the Sheet Metal and All workbenches. Type code SM.FILLET (short name SM.CFIL).

Walkthrough

Recorded from the running app by BREP_mcp/tests/videos/sheet-metal-corner-fillet.json; regenerate every walkthrough with ./build.sh docs-videos.

The flat is seeded off camera (4800 mm³, asserted). The pick is the flat's own top face, which the corners field reads as every corner of that plate, so one click treats all four.

The volume drop is exactly what four rounds take off a 2 mm sheet: 4 × (1 − π/4) × 6² × 2 = 61.805 mm³, leaving 4738.195 mm³.