I know, Rhino is not meant to be a MCAD. wiki.mcneel.com/labs/advancedflattening:
Rhino 4.0 does not have:
Unfold or unbend - to make a flat pattern from 3D shapes made from bending up a 2D pattern. Mostly used to create sheet metal cases, etc. Most MCAD products do this nicely,
We still sometimes do this with Rhino, as it makes no sense for us to invest 6k euros for just an Unbend Software.
As Rhino principially has all you need on board, I believe that it would not be too complicated to improve the workflow a little bit. Could make Rhino extremely interesting for a lot of small metal fabricators, I believe.
BTW: WIP crashed, when I tried to print this to pdf …, this printout is V5 with 7-pdf printer
metaRhino unbend.pdf (163.3 KB)
Yeah, I don’t think you can practically do sheetmetal features without going all the way down the feature-based rabbit hole–or at least it doesn’t make a ton of sense to try to, it’s kind of inherent to the concept. I’ve watched engineers working on really very modestly complex assemblies with metal-formed features and having all sorts of weird problems due to their quirks vs the regular modeling tools.
Of course Rhino has various ‘unbending’ tools, just not the ones for basic bends. I mean I’ve used mid-surfaces to get approximate dimensions for quoting, but for CNC forming the supplier winds up rebuilding the model in Inventor or whatever, which is really not bad since what I’ve read about the k-factors is they can be machine-specific, as long as no one enters one number wrong and $25K of aluminum and fabrication has to be junked!
We are metal fabricators, having cnc punching equipment and press brakes in house. It is true that building these parts is not easy. I can adjust k-factor by offsetting the surface not to the middle, but a bit further away. I can than check the unfolded length against parts we´ve made before, and adjust the offset. In reality k-factor calculations or tables are - depending to the part - not really useful, as unfolded length depend also to the press tools we use, actual material thickness and grain direction, hardness and alloy. We´ve also seen differences in one charge of alu material, which might be due to the fact, that the material behavior depends to uncoiling the material. Therefore we still have to make tests with every new charge of material, and have to adjust the (CNC) Press Brakes and the unfolded shape for every production run manually. I don´t think that Inventor or Catia would help that much, we still would have to adjust the CNC programs. I think this is true for most companies.
Sheet metal fabrication is a minefield - bending machine, stock type, thickness, tools, angles… It also very much depends on the kind and complexity of the products. We had good success using Grasshopper and a bending table for simple polygonal products, derived from bending the stock to be used in 10° intervals, so when flattening, Grasshopper can handle the bending deduction/allowance. But, really, it’s better to use Creo or SolidWorks if one needs reliable output on a daily basis with constantly changing products; so much time and money can be wasted when things go wrong