I’m new here and just want to register my interest in this thread as it covers an area that I’m finding difficult to bridge. I’m currently migrating from Fusion 360 to Rhino. Primarily because I have a lot of past AutoCAD experience and prefer the command driven interface. I also want to move from a subscription model to a perpetual licence.
I’ve made extensive use of the sheet metal functionality in Fusion, which is really good, primarily for designing accurate heat bent acrylic sheet parts. Being able to generate a flat pattern from a fabricated part for export to CNC is very useful. So I’m now trying to find the most efficient way of simulating this in Rhino.
If sheet bending in acrylic can be approximated with a neutral line at the center of the sheet then you could use that to model and use Unrollsrf to flatten. If the neutral line cannot be approximated like that it will require more hand work to get it done. If the parts you design are somewhat parametric a solution using grasshopper could work as well.
Thanks Gijs. I’ve seen some impressive results with grasshopper, one of which was simulating a sheet metal bend, but it was a short video just showing the result, not how to get there. Do you know of any good videos / tutorials to get started?
I’ve been experimenting with the UnrollSrf command to, which is a great feature! Also been working the other way around, so starting with a top view 2D profile drawing (for CNC export), then using the same geometry to introduce 3D bends and build a solid model via OffsetSrf for acrylic thickness.
Really like how there are many possible approaches to get the same result.
If you need to do “sheetmetal features” then just use software that has them, it’s a very specific feature set that Rhino simply does not have and never will unless you want to build them yourself from scratch, which is hardly worth the effort. If accuracy is not really that important then you can make the “mid surface” and unroll that. If that’s not good enough, you’re wasting your time.
Are you actually making these items yourself or sending them out? If someone else is making it then just send them the 3D of what you want and they’ll rebuild it in SolidWhatever and have the K factors set precisely based on the quirks of their machines and the phases of the moon, it’s a black art.
I couldn’t agree with this more. If you make sure your file is clean, the parts can be loaded in 3rd party software and reinterpreted as sheet metal parts. The added advantage of this workflow is that you place responsibility of the actual part at the manufacturer.
The sheet metal manufacturer I have been working with closely, always bends some test pieces and calculate the bend factor from those. For every project.
Can’t share it, but I can tell Rhino.Geometry.Unroller is a perfect start, then you exploit it and correct the bent surfaces into proper dimension using the K formula.
It is giving me congruent results with Inventor’s… apparently.
I consider starting surface to be the center of the thickness, so when found a cylindrical surface i arbitrarily take its radius and remove half thickness to get the inner radius (of the bending machine blade…).
Works only with poysurfaces which have only clean planar surfaces and cylindrical bends, but as far as I’ve understood other tools have a similar limit.
It’s 280 lines of code, it’s even multithreaded (I’m creating hundreds of different pieces in gh, flattened and exported in dxf in under a minute, sadly dxf export still rely on adding to rhino document, selecting, launching silent rhino command “-_Export” )
I’m sure you devs can make a better tool that also can accept the outer/inner shell of a sheet metal object, and using normal it can understand if each bend is the inside or outside (so to subtract or not the thickness before the K formula…)
Yeah, I mean it led to an assembly of $20K in bent aluminum that fit together perfectly being entirely the wrong size once, but let the manufacturing experts handle the quirky highly variable manufacturing process.
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