Sheet Metal Hem

Status: Implemented (Rust-kernel-backed)

Sheet Metal Hem folds an edge of an existing sheet-metal body back on itself: a flange with the angle locked at 180°.

Inputs

• id – string, default null. Optional identifier for the history entry.
• faces – multiple reference_selection (FACE or EDGE, default null). Sheet-metal side-face or hole-bore overlays, or rim edges naming those faces, to hem.
• useOppositeCenterline – boolean, default false. Flips fold direction.
• flangeLength – number, default 5. Hem leg length.
• edgeStartSetback / edgeEndSetback – number, each default 0. Trim the hem span back from selected edge endpoints.
• inset – options, default Material Inside. Where the hem sits relative to the reference edge, an inward fold-line shift applied before the bend: Material Inside (default) = thickness + bendRadius, Material Outside = bendRadius, Bend Outside = 0.
• bendRadius – number, default 0. Inside hem radius; 0 is a knife hem. Because a true zero radius cannot revolve it is interpreted as 0.0001.
• offset – number, default 0. Signed bend-edge offset (positive = outward, negative = inward).

Behaviour

• The fold is always 180°, and flangeLength is the return leg measured from the bend tangent (Tangent to Bend); neither can be changed.
• The body is rebuilt in place under the same name, and the hem appears in its flat pattern.

Walkthrough

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

The same stage and the same rim pick as SM Flange; what the walkthrough is for is the difference. A hem's form has no Angle field at all — the 180° is the feature, not a setting — so the length and the bend radius are the only shape knobs.