How to Work with Hems in BricsCAD Mechanical

Quick answer: A hem feature forms when the edge of a sheet metal flange folds back on itself. SMHEMCREATE simplifies creating them, confirming exactly the command covered on this hub’s Sheet Metal Commands page. Hems carry their own set of properties depending on their type, the “flange” and “bend” type geometry involved, get recognized by SMCONVERT, and display with a special symbol when unfolded with SMUNFOLD.

Creating a Hem

1. Select several linear edges on the flange, or hover the cursor over a single one.
2. Launch SMHEMCREATE via Create a Closed Hem in the Quad menu, the same tool on the Sheet Metal ribbon tab, the Sheet Metal menu, or the command itself.
3. Hover the cursor to adjust the hem length.
4. Use the Ctrl widget or the Toggle tapering option to flip the adjustment relative to the edge.
5. Press Enter when finished; the hems, along with auxiliary features (reliefs and miters), create.

Modifying Hem Parameters

Select the hem feature and adjust it in the Mechanical Browser; the available parameters depend on the hem type.

Whatever parametric change you make, the hem type stays preserved, and the geometry moves inward to maintain the part’s external dimensions.

Erasing a Hem

BricsCAD intelligently restores the geometry’s dimensions and reliefs when a hem feature is erased. Starting from a flange part with external dimensions of 100:

1. Use the Width option of SMHEMCREATE to create a partial hem on a single edge.
2. Create hems on two other edges too; this produces fairly complex relief geometry, but the part’s external dimensions stay preserved.
3. Select the hem features and delete them; some imperfections remain on the corner relief feature and the imprinted edge.
4. Delete the corner relief feature as well, then run DMSIMPLIFY to restore the original part with its original dimensions.

SMDELETE Behavior on Hems

SMDELETE restores the hard edge between two flanges when removing a bend or junction, removes a flange along with all its adjacent bends (extending the neighboring flanges up to a junction configuration where the deleted flange was), and restores geometry that a miter had removed, confirming exactly the same behaviour covered on this hub’s Sheet Metal Commands page.

Frequently Asked Questions

What happens to a hem’s type if I change its Radius or Length parameter? The hem type stays preserved; the geometry adjusts inward to maintain the part’s external dimensions.

After deleting a hem feature, why does the part still look slightly off? Some imperfections can remain on the corner relief feature and the imprinted edge, delete the corner relief too and run DMSIMPLIFY to fully restore the original geometry.

Which parameter changes a Teardrop hem’s angle rather than its length? Radius, changing the angle; Length changes the hem’s length instead.

Do hem features show up automatically when a part is recognized by SMCONVERT? Yes, and they display with a special symbol once unfolded with SMUNFOLD.