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Calling all sheet metal experts!

Got a challenge here that so far has me stumped. If you'll look at the attached file you'll see it's basically a box with cut outs on each side with the corners filleted with a 3" radius. The metal thickness is (10) gauge 304 stainless. Now how do go about doing a flat layout of this baby? The corners are the sticking point. Thought about just using 6" sch.40 pipe for those but still there is the problem of filling in the void at the top where they meet. Any and all suggestions welcome!

By the way, using latest V15 for this. May not be capable for this - yet!


  • Of course, a lot depends on the final usage of the product, and how much the aesthetics matter.

    Buy some spheres. Spheres have to be formed or cast.  Since you already mentioned the pipe, I think you have the right idea of finding something already made, and cut it and attach it the same way you are going to do your pipe. There are stainless steel bowls for cooking, though they are not as thick as you may want.  I just did a quick internet search and found that stainless steel spheres are surprisingly affordable.  This site has some in the sizes you would need, and in a variety of wall thickness.

    Change the design to be faceted, so that you don't have that 6" diameter spherical shapes on the corners.  If all the edges are changed from that large radius, to a faceted design, then it will be a lot easier.  Even forming 3" radius bends wold be a challenge in many shops. 

    Make the spherical corners partially faceted.  If you are using 1/4 of a pipe for your vertical corners, then cut the top of it with perhaps 3 gores (like how the fabric for a balloon is cut) and bend those gores to the 3" radius.

    Change the materials for those spherical corners. Can the spherical corners be made from another material entirely?  Perhaps plastic or rubber? Rapid prototyping can be used to make a spherical corner, with perhaps some extra tabs to allow it to snap in.  You may even be able to have it electroplated to get a nice finish, though the part is still not going to be as strong as if it were all formed of 10 gauge stainless.

    Can you tell it is a slow day at work for me?  

  • Joe, thanks for replying. It's a dryer of sorts so it has to be stainless and the 3" radius is what the customer wants. Your idea of spheres is interesting though, I'll check it out.

  • I would form the piece from a sheet without the pieces for the corners, you could bump roll the sheet to form the 3" radius corners, or you could possibly use a break with a die to form round corners.  For the corners, develop a flat pattern of the spherical shaped corner make it slightly oversize, find a 3" radius object that is hard enough to use as a dolly heat and hammer the little flat pattern to form a spherical corner, trim/grind the corner to fit, then weld in place.
  • Here's an idea (maybe a bad idea!).  Spheres can't be unfolded, so replace them with flat plates.

    Model the box as a solid.  After filletting the edges, cut the corners completely off by subtraction.  Shell to 0.135 thick.  Use Extrude to punch out the corner facets.  Use subtract to split the end flanges for unfolding.  I think it needs 'rethicken' and I'm not sure BriscCAD can do it on this model. 
    Convert to sheetmetal and unfold.  You will need to make 4 flat shapes to fill in the corner holes.  It's not very pretty.

    15J3614-plenum layout idea.dwg

  • Attach my take on this. The part is very long, so I've split it into 3 parts. Two ends and a mid section. For the ends I created addition flanges (shown in Red)  that would need to be removed after the folding process. I did this because BricsCAD sheetmetal doesn't like having bends without a connecting flange. If you look at the part without flanges in the Mechanical Browser you'll see that the bends are marked red indicating there's an issue. In any case you can always post edit the flattened profile to make adjustments.

    The corners can't be done in sheetmetal. I would talk to a company that does Metal spinning. They should be able to easily create these for you.


    Jason Bourhill

    CAD Concepts 

    15J3614-plenum layout-ccl.dwg

  • Many thanks gentlemen for all the ideas! Decided to flatten without the corners (no choice really!) & order 6" diameter hemispherical shells, cut to fit. Like you said, not pretty but serviceable - I hope! Appreciate the strides Brics has made in modeling, looking forward to more "toys" when V16 comes out.

  •  I'm using V15.2.06.  I could not unflatten this until I used the SMCONVERT command.   That put small relief holes in the corner, and I was able to unfold it.   I do a fair amount of prototyping work on an old pan brake, and it looks to me that you would start by bending the wide end up.  Then the bend both long side flanges, then bend up the small end.  If you wanted the small relief holes removed, you can weld them shut. 

    15J3614-plenum layout_unfold.dwg

  •  Excuse me.  I meant to suggest a PRESS BRAKE.   The output of BricsCAD's sheet metal flattening routine places bend lines in the center of the bend radius.    A pan brake needs to grip on a flat surface, outside the bend radius.   Since there is no flat surface to grip in the corner posts, you couldn't form them with a pan brake.    

    Then too, I just noticed the scale of this design.   (I thought it was millimeters, but I see it is inches.)    It would take a very large press brake to bend the radius on the long axis.
  • Excuse me.Maybe plastic or rubber? Rapid prototyping can be used to make spherical corners, and there may be some additional tags that can be added to it. You can even use electroplating to get good finishes, although this part is still not as if it were made entirely of stainless steel

This discussion has been closed.
Origami is the Japanese word for paper folding. ORI means to fold and KAMI means paper and involves the creation of paper forms usually entirely by folding.

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