Hey Guys. I’m getting a little frustrated with Rhino here. I’m struggling to figure a workflow that works without constantly breaking my surface or mesh.
SolidFillet on a polysurface constantly breaks edges based on what I see in “showedges” I have to constantly mess with the order of how I fillet the solid. i.e. do these 4 first, then these 2, then this one and in that specific order, or the solid folds over and breaks. It’s a constant game and a waste of time, until I get the part to close (leaving just the opening on the bottom).
After making a surface of a part, I need to do two things. Offset the part by 1mm to create a test file, and then offset the original part 2mm, taking the outer “shell” to make the mold. If I try to "add thickness by using offsetsrf and creating a closed solid, the part breaks and I’m left with more holes in the outside of the part. Are you saying that I need to remake the part twice at different sizes and then connect the two? This is what I’m seeing on the forms. Are you kidding me? What’s the point of offset surface, when you can’t offset a surface? The only way I’ve been able to get around this is to convert the polysurface to a mesh and then either extrudmesh or offsetmesh to get mesh to get thickness or offset I need. Photo below is result of a offsetsrf.
Ribbonoffset works about half the time and I don’t understand why. Since I can’t use a polysurface, I have to use the mesh created in the previous step (part is turned upsidedown to create the mold). I duplicate the border (dupborder), then try to perform ribbonoffset, but nothing appears. I’ve found that moving my cplane seems to help here, but it works 50% of the time, even when the cplane is in the same position. i.e. I place the cplane on the mesh and it works, then I copy and paste the mesh, place the cplane on the same spot and orientation on the new mesh, and it doesn’t work.
Then of course, I have a mesh part, with a polysurface from the ribbonoffset. I take a dupborder of the ribbonoffset, set the thickness to 0 and move it to the bottom of the part, Planarsrf the flattened dupborder and loft the new surface to the ribbonoffset, to create a solid mold with a flat base (figure below). I can quadremesh the larger polysurface, but it still leaves a border between the original part mesh, and the ribbonoffset mesh which wont close (2nd figure below). Plus whenever I switch to a mesh, I lose part quality/accuracy. Shrinkwraping the part looks like trash and I can’t work with that.
This aside, I’d rather be performing a ribbonoffset on the polysurface so I could maintain 1 large polysurface, rather than having to convert everything to a mesh as in the previous paragraph. I need to put a 2-3mm fillet between the part and the ribbonoffset so the edge isn’t so sharp (essentially a fillet where the pink line is).
I bought Rhino because It’s known for being a great mesh modeling program. It handles the larger meshes that I’ve scanned significantly easier than Solidworks which can barely open the file. However, having to use meshmixer to fix my meshes since Rhino cannot do so (per my other forum post), struggling to work with Rhino to clean up meshes thereafter, and dealing with the above, I’m really starting to wonder why I just spent $1K for a program when I’m not getting what I need.
P.S. My long term hope with Rhino, was to be able to automate everything after I created the original part (using grasshopper)… Not sure if that’s doable at this point..
Thanks for looking into this. No not exactly. I’m trying to solve 3 separate issues. The file shows the part at different steps and incurs all 3 issues. I’m using this part as an example, since it’s small and shows all 3 issues I’m dealing with.
Issue 1: Fillet
Whenever I try to fillet a part, it always results in edge gaps as shown in the photo above (using show edges command). This creates a lot of issues when I continue to work with the part. Since this post, I’ve switched over to using, blend edge, which seems to work better, though I still have some issues..
If you take a look at my file, it’s the 1st tan colored part that I’m trying to fillet. I was able to get this to work successfully as shown in the middle tan colored part, but that was only after trying 20-30 iterations of, running the command and changing which edges to fillet first, then restarting the command with the 2nd set of edges, then restarting again for the 3rd set of edges, etc… While the program lets me fillet all of the edges and change fillet sizes upon running the command only 1 time (set size 1 and select edges, then size 2 and select more edges, etc.), doing so results in an open part as seen in the photo from my first post.
Issue 2: Offset/extrude/shell to create wall thickness.
The second issue is regarding creating a thickness to the part by using offsetsrf (extrude and shell don’t seem to work right?). I am unable to successfully create a closed solid to work with.
As seen in the third photo (blue part) from my original post, there are still issues. The only work around is to convert to a mesh and offset from there. I’m trying to understand why this and I’m trying to stay in polysurface so I can effectively work on the part after performing the ribbonoffset (3rd issue)
From what I found on Rhino forums, people were saying that I needed to completely remake the part at the larger size and then combine the two. That’s ridiculous and completely defeats the purpose of extrude or the offset command.
Issue 3: Ribbon Offset not working
Ribbonoffset command does not work very well at all. Upon taking the original part, performing a “dupboarder” command to get a curve outlining the boarder (edge), and then performing ribbonoffset on that curve, it won’t show the ribbonoffset, or it will show it inverted, or completely messed up.
Looking at comments in the youtube explaining this command, other people were having issues. From what I’ve found, you have to adjust the c-plane to be located on the curve, and flat with the plane that you wish the ribbonoffset to be (i.e. horizontal with the part). Then you have to create the ribbonoffset using the “TOP” view. It cannot be done in the “perspective” view or it breaks the command. Sounds like it’s a bug. It would have been nice if that were better documented somewhere other than the youtube comment section.
Issue 4? - fillet (again)
This is what I brought up at the end were I wanted to fillet where that pink line was located (in the last photo). I cannot fillet the part because the part is a mesh, and the ribbon offset is a polysurface. I had to switch from a polysurface to a mesh to get the offsetsrf and ribbonoffset to work (workaround for issues 2 and 3).
What I’ve found here, is that if I try to go from the polysurface to a subd or nurbs, the part looks bad, but if I change the part from polysurface, to mesh, then to subd, and then to nurbs, I’m able to maintain part quality. I cannot go direct from polysurface to subd or nurbs. I found this workaround buried somewhere (I’ve forgotten at this point, but it works).
Since Nurbs is a polysurface, I can then join the original part with the ribbonoffset that I had created in issue 3. Once joined, I can use the blendedge command to fillet the edges originally discussed, between the part and ribbonoffset (solving issue 4).
The nurbs part, also seems to work better when creating a ribbonoffset, than a polysurface does. I’m not sure why that is.
If you have any insight as to why it’s so hard to fillet edges on a part, any tricks to using ribbonoffset, or creating “thickness” to a polysurface without creating an open part, I’d love to hear more.
