Associative Unfolded Representations of 3D Solids in BricsCAD Mechanical Explained

Quick answer: BricsCAD offers bidirectional associativity between 3D sheet metal entities and their flattened representations, expanding the Associative option mentioned on this hub’s unfolding sheet metal parts page. Each version stores in a separate document: the original part in its native document, and the flattened part in a temporary one. This associativity stays active only while both documents remain open; closing them, or starting a new BricsCAD session, requires repeating the setup.

What Associativity Means

Associatively unfolding sheet metal entities lets you modify the flattened geometry and propagate those changes back to the 3D model, useful for two main purposes: creating complex, non-standard bends and corner relief cuts, and avoiding self-intersections during unfolding. Since it’s bidirectional, changes transfer both ways between the flattened entity and the 3D model, applying to whichever representation becomes active.

Turning On Associative Mode

SMUNFOLD turns this mode on. From the Sheet Metal section of the ribbon, select Associatively Unfold Body and choose a flange face. BricsCAD flattens the selected entity and switches into associative mode, successful as long as it meets the same criteria as a regular unfold; continue only if no errors or warnings appear.

A temporary document containing the flattened entity opens, no need to save it, it exists purely to propagate edits back to the 3D model. In the Mechanical Browser, selecting the flattened geometry lists its disabled features. Click Vertical Tile on the Toolbar or Ribbon (confirming WVTILE) to arrange both open documents side by side and zoom into the collision area.

Editing the Geometry: Adding a Custom Corner Relief

1. In the flattened design document, draw a circle at the corner.
2. Apply DMEXTRUDE to that circle and subtract the resulting volume.
3. Click the original document to make it active again.
4. The model updates and the custom corner relief appears, with the Command line reporting “Changes were successfully transferred to source model.”

Avoiding Collisions in a Flat Pattern

Fix geometry collisions in unfolded sheet metal entities by modifying the flattened geometry through associative unfolding.

1. From the Sheet Metal section of the ribbon, select Associatively Unfold Body and choose a flange face to unfold (use Vertical Tile to view both the 3D model and the associative unfolding document at once).
2. In the unfolded drawing, draw a polyline along the edge of the collision.
3. Run DMEXTRUDE on the polyline, then DMTHICKEN the resulting surface.
4. Subtract that thickened body from the unfolded sheet metal entity.
5. Erase any leftover pieces.
6. Click the original document to make it active again.
7. The collision, now resolved in the flattened geometry, propagates back to the original sheet metal entity.
8. Optionally export the file as DXF to test the resulting 2D unfold.

Frequently Asked Questions

Does associative unfolding stay active if I close BricsCAD and reopen my files later? No, associativity only remains active while both documents (the original part and the temporary flattened one) stay open; you’ll need to set it up again afterward.

Can I use associative unfolding to avoid self-intersections in a flat pattern? Yes, that’s one of its two main purposes, alongside creating complex, non-standard bends and corner relief cuts.

Do I need to save the temporary flattened document created by associative unfolding? No, it exists purely to propagate your edits back to the 3D model.

How do I view the 3D model and its associative flattened representation side by side? Click Vertical Tile on the Toolbar or Ribbon.