Can someone show me how to fold the magenta plate to become the blue one?

reverse engineering a bracket.

I have a trace of a metal plate (inner surface non stretch) after it was folded and laying it out on paper it shows me the plate before folding and importantly the size and location of ‘the arch’. I now recreate that in 3D. (magenta)
I want to use it to establish where the curved arch will be on a folded item. (blue)
the fold has inner radius 0.05inch, outer stretched radius 0.08 inch.

How do I take this and fold it through that radius to see where the arch sits ?
then I can plot the result on the blue upright, who’s upper extent is sketched by the way. (bears no resemblance in height or width to that area, ditto that part of the ‘pink’ flat plate, just again an arbitrary shape, enough to show me where the arches will be, to then draw that area accurately.

see attached
folding the trace though 90degs.3dm (300.7 KB)

maybe this Grasshopper code is the fix ?
Can i use this on this and how much time will it need to use it as I have no experience with GH at the mo, and GH not installed, I have V5 and win764bit pro so will GH work ?

Could someone just bend it with their GH using this code in this thread above, get me out of my immediate need pleeeese .

Asked and answered in the other thread.
I’d suggest hiring someone with sheet metal tools to help with with your short term immediate need.

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hiring someone to do the sheet metal bending ?
see what I need sheet bend for.
Hiring not applicable at all,

John, you say…
I’m not aware of any plug-ins either.

Is not the Grasshopper fold above link to, by Seghier Kaled, a solution that Rhino can use ?

I ask…Could someone just bend it with their GH using this Seghier Kaled code in this thread above, get me out of my immediate need pleeeese .

Check this , if that what you want (44.8 KB)

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Hi, I need scale Y to be further forward.
How do you position the axis of the bend, as I can see that with minimal Y value it is not forward enough and where my bend should be ?
see my post on the forum. I had an arch in my original drawing

and need to see where the accurate trace of the object puts the real arch.

I look fwd to trying Grasshopper and your code.
Have you refined it as it has a different name ?


This is simple 2D stuff:
Make your inner curve as 2D curve
Make a line on top of your flat part
Turn on history
Use flow with copy and no stretch
No need for grasshopper
No learning curve, well a super short one
Works in rhino 5
Adjusting either curve or the flat part updates the bend part

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Thanks Gijs,
sounds similar to this method Mristau has just posted. No one has suggested this before for sheet bending hence my not trying it. Folk making grasshopper bend tools etc.
SheetBends [Converted].pdf (5.7 MB)


I think it’s better to put the reference and target curves in the middle (Thickness) of the piece you have. So far his method is the best for your simulation and you can control your bending radius. (42.7 KB)

that worked a treat, so simple as well , I owe you a pint :slight_smile:
No one has ever suggested that for the sheet bending.
Mristau had the same method in his pdf.

Mahan…do you refer to Seghier Khaled’s grasshopper solution as you supply a .gh file so I think you do.
I am totally new to GH and have just installed GH on V5.
Havent a clue yet on how to make use of a gh file, how to run GH etc, (need to do some tutorial viewing) so cannot follow suggestion until I get to see how to run GH and make use of a gh file. see what this gh file gives me etc.
Am I right in thinking he has also used a base line and target line from what you say ?


Yes. I was refering to @seghierkhaled 's method. For flowing a geometry along a Curve, you need a base curve (Reference Curve) and a target curve . It’s just the matter of positioning these curves in the right place. If you can manage to open the grasshopper, the rest is easy since you just need to alter the slider (43.1 KB)

I wonder how one changes the actual axis of the bend as its happening further back than it should in the video for a 0.05inch rad inner curve. The flow method I used uses a target curve placed exactly where the surface neds to end up with a inner radius of 0.05inch.
No doubt I will find out when I find out how to run GH and use this .gh file.

Btw: I want to clarify that this method I suggested is more like a quick fix than a correct way of modeling, but it will give an accurate result to get an idea of where your part will end if you want to reverse the process. Normally It’s easier to work form 3D to 2D using unrollsrf. This can also be grasshoppered.

The neutral axis is between 0 and 0.5 x plate thickness and depends on corner radius and bend method. For thin sheet with sharp corners it’s close to 0. I’m currently working on a project with 8mm thick free bend steel. With an inner bend radius of 15mm the neutral axis ended up being at 3.5mm from inside radius giving a k factor of 0.4375, and some parts with inner radius of 4 need a k factor of 0.33

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I had the good fortune to find Pavlos Marinis on couple months ago. Helped me with three small projects that were beyond my skill level. Congenial, fast and recommended.

Just try doing the sheet metal stuff in Fusion 360 and then export and load in Rhino.

Hi jodyc111
Siemen and Gustavo I see have beaten you to it for suggesting Fusion360, free, but alas no longer, so they say.
I will add your suggestion there on what was the prog thread.

I bought the first version when it first came out and it was two years subscription at a heavy discount. It timed out and I signed up for the free version and it is still working, I think, better look as I haven’t used it lately.

I love it for making nice shop drawing DWG's with fancy title blocks and annotations from my Rhino models. If there was a direct 'cut and paste' between it and Rhino it would be great but I doubt that will ever happen. Unless you are making over $100,000 a year doing your work you should be able to get the start up version for free. You will never make that kind of money agonising over those little folded brackets! Good luck on it all.

Thank you Jodyc111
you got it at the right time.
I will explore and ask them nicely if I can have it for free.
I also have a friend also into aviation and he has autocad, he didnt realise it didnt do sheet folding and fusion360 would suit him as well, if its free. We dont charge clients, so free or affordable is what we need.


Hi Mristau,
Useful site, I wonder if they have any clients wanting vintage aircraft parts reverse engineered ?
I cannot pay anyone, I need folk to pay me but the amount of work required in what I do if charged for would see folk run away.