FreeCAD Forum

I finally played with SheetMetal workbench, and I realized that it might also be a platform for parsimonious modelling of plastic as well as metal boxes.

When I design plastic boxes to print, I sometimes want rounded corners for comfort and/or aesthetics, and adding fillets is finicky selecting all the edges. We're often advised to add them all at the end because they will break and you'll just have to do them over again. But SheetMetal Bends look pretty nice...

I found that setting min gap, offset, and radius to 0, rotating a corner, and then mirroring the rotation twice gave me a beautiful box. So far, not that much different work from from sketch, extrude, plane, sketch, pocket, fillet.
However, if I choose the axis of rotation properly for the edges, the angle of the Bend lets me set a draft angle. For example, here it is with a 2° draft angle:
This way I end up with a complete box, which can be printed but also is appropriate to mold from the same design, with a very simple (I think) design tree driven only by a single rectangle sketch.


The nice thing is that this still applies for more complicated boxes, even ones which can't actually unfold as sheet metal, like this:

This preserves all the necessary draft angles so that it could still be molded. Closing the bottom of an inside corner takes a bit of work, but nothing too bad; just a couple of pad-to-face (or to a datum plane).
Is this one of those known techniques that I just now stumbled on?

Thanks for sharing. Interesting way to get the corners.

I'm so glad I posted this. It meant that I had documented it for myself and this morning when I wanted to design some watercolor trays for a family member, it was easy to remember... Here's a set of full, half, and quarter pan watercolor trays. These are sized for the inside because a watercolor pan is defined as 20x30mm, and I made these 1.5mm thick both to be strong and to have a little weight. But it just needed three size changes and one parameter change from outside to inside dimension.

Did (and if not, would) you x-post this to the official sheetmetal forum thread?
It may be worth documenting for the official sheetmetal workbench...?

Kunda1 wrote: ↑Sat Dec 25, 2021 4:49 pm Did (and if not, would) you x-post this to the official sheetmetal forum thread?
It may be worth documenting for the official sheetmetal workbench...?

I completely missed that earlier. Can do that now.

It no longer works as posted, because of the new restriction that mirrors can't be mirrored.

So I've updated it to use a MultiTransform in 0.21 weekly and attached it.

Here's a screen shot showing how setting a bend angle of 88° a 2° draft angle is created for the walls.