I've recently was handed some Rhino files to try and work with, because the rest of our team was having trouble manipulating them. Given my SolidWorks experience - I'm fairly comfortable with surfaces - I thought, how bad can they be? Bad. And by that I mean where a surface should most definitely be planar, it isn't. I've attached a small portion of a decently complex model (can't upload the whole thing for business reasons) to demonstrate this.
In the file, you'll see were there is a depression in the surfaces, where a model of a lid would go. While the lower faces or this "dish" are curved (and that's fine), the wall faces - those that have a slight draft for molding - have no planar sections in them. Not even after trimming (see image "No Planar Face"). Absolutely everything in this model is a spline curve, even where it is obviously a straight line. Now, I am aware that Rhino is a NURBS based modeler. But I also know that it is capable of making straight lines and fillets.
So why is this a problem? Because I need to modify this model to include some cutouts and positions for a hinge on the lid, and tabbed cutouts with hinge holes on the main file. Which means I'd like to use the existing surface, and extend it, so that I've got a nice, clean face for manufacturing. Take a look at the image "Extend Surface". Despite having trimmed the surface far enough back to where I know it should be planar, once I extend it past a certain point it magically curves back to exactly where the original surface once was. This makes the existing geometry, as given to me, basically unusable to reference for modifications.
That should be enough background info for now. So here are the questions...
- Is there a way to import Rhino models to include or force the use of "rational geometry" (arcs, lines, circles, etc.)?
- If not, is there some easy way to convert that existing geometry in SolidWorks, so that behaves how I need it to?
- Or are my previous questions moot, because the real issue is the Rhino use made everything out of splines to begin with?
I suspect the last question might be part of the reason, but since the surfaces don't seem in any way mirrored (especially not in the large file), my guess is there is something being lost in translation. One last note - the imported files were exported from Rhino as a STP file.