Is there a command for Rhino 8 CAD for adding a bend (e,g, 90 degree) to a rectangular solid, with a) Bend Axis, b) Bend Radius, C) Bend Angle? I want to use for sheet metal panels for architectural roofing, BUT the existing “BEND” command in Rhino does not seem to work. I know how to calculate Neutral Axis, and Bend radius based on the material being used and its thickness, BUT there does not seem to be a Rhino command for this level of control in bending a rectangular solid so the *.stp files I export are NOT recognized by the online sheet metal fabricators. Please advise ??
Hi the “bend” command is simply and absolutely not for doing sheetmetal bends, it’s for fun freeform editing. Rhino does not have “Sheetmetal Features.”
To model such stuff in in Rhino, you just build the “bends” as you want them to look using regular geometry, usually fillets. When you send them to a fabricator to be made they will rebuild them in their own software with their own k-factors–every step of that process is what you call a “black art”–that and you absolutely want to just leave them to it, so it’s entirely their fault if $20K of aluminum turns out the wrong size, ask me how I know.
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Nice website on your bio Jim. Thanks for the response.
To add to @JimCarruthers response, you can model bent sheet metal in Rhino, but not the way you’re doing it.
Model the folded part without thickness. I use the mid-plane, but it depends on fabrication processes. Then UnrollSrf this to give the flat pattern and bend lines. I model the mid-plane bend radii and use TweenCurve on the edges of the radius from the flat pattern to get the real fold centreline.
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May i pitch SheepMetal for that.
You can model a none-manifold brep in rhino and reference it in grasshopper. SheepMetal has a none manifold to sheet converter, that applies correct bend radi and thickness. Finally you can also unroll that sheet with the K factor for more precise fabrication.
For the moment there is no rhino plugin, but there will be maybe one in the future.
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Hi Nick:
Thanks for the response.
So you will end up with flat file, suitable for .dxf export to sheet metal fabricator, yes? I am not sure how tween curves helps find the neutral axis or if that is even necessiary since the neutral axis is: R_neutral ≈ R_inside + (thickness × K)
I am trying to export 3D .stp which fabricators also work with, but Rhino export in that format does not recognize the bend, perhaps because Rhino 8 CAD just works with surfaces, and does not record the ‘neutral axis’ of the bend which Fusion 360 does.
Thanks for the Info Felix.
Yes, DupBorder to get an outline that can be exported to dxf.
TweenCurves isn’t giving the neutral axis of the bend, it’s just a trick to mark the centre of the fold.
The model. Mid-plane polysurface with correct radius bends.
Flattened polysurface of same part (UnrollSrf) with bend extents in black and TweenCurves gives the centre of the bend extents (yellow).
Not perfect, but good enough.
Thanks for the follow up Nick. Much appreciated.
The k-factor of our production conveniently puts the bend plane at the mid-plane. So use whichever k-factor and “mid-plane” you need for your production.
Thanks for the follow up Nick. I am ok on .dxf but what I ‘wish’ for is going directly from Rhino 3D to export selected of object in .stp file format, which online sheet metal shops like SendCutSend will take BUT apparently NOT from Rhino (yet) because Rhino apparently does not handle the bends at a .stp level in the same way as Fusion 360 does. RHino =?= 2 surfaces rather than surfaces derived from a bend (neutral) axis. When I upload such a *.stp file of a simple “L” shaped object intended for sheet metal with a single bend (90 degrees) the upload works from fusion 360 BUT Not from RHino. In the case of Rhino all that shows up in SCS is one leg (not both) of the “L” shaped object.
Strange, I wasn’t aware that STEP format had anything parametric in it (like bend characteristics). I thought it was just a “dumb” file format.
So it’s looking for a thin surface model instead of solids? That is what Nick describes making….
Like IGES, STEP is “dumb” insofar that it is a software-agnostic 3D file interchange format.
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