Newbie -- Problem extruding adjacent closed curves

Hi guys – Brand-new member here, and Rhino 8 beginner. I’d appreciate it if someone could help me with this problem I’m having. I’m doing a practice model, and am trying to extrude a base plate that has some vertical cylindrical bosses that are taller than the plate is thick. The bosses are also tangent to the perimeter of the plate. (please see attached pic) I would like to extrude the bosses, and then extrude the remaining, shorter, area of the plate that’s touching the bosses, but can’t seem to do it. When I select all the curves via windowing, and either make them into a planar surface, or just extrude them as curves, only the circular bosses are affected – Rhino doesn’t recognize the center area of the plate as a different closed curve. On past practice models, it seemed as if I would have to redraw some of the shared curves that were used in the first extrusion in order to extrude the second area. This seems REALLY unwieldy, and I’m wondering what I’m missing. Can Rhino not do separate extrusions from curves that have shared edges? I used to practice a lot with Designspark Mechanical, and it was very easy to extrude different closed areas that happened to be touching – just passing the cursor over an area would highlight it as its own separate, extrudeable, closed curve. Thank you for any help anyone can offer. Rhino is turning out to be a bit tougher to learn than I’d expected.

@Drew_Joseph Do you want your final result to looks something like this?

I’ve read your post several times and am still not clear on exactly what you are try to do, nor what steps you have tried. There are multiple ways to arrange the curves in your image.

What do you mean by “curves with shared edges”? Do you mean curves which partially coincide? (In Rhino surfaces have edges, curves do not have edges.)

Upload a .3dm file with your curves. Drag the file to where you type your post, or use the vertical arrow icon above where you type your post.

You mentioned using Designspark Mechanical in the past. Have you worked through any Rhino tutorials? Or with your previous experience are you trying to just jump into Rhino and start modeling? If the latter I strongly suggest taking the time to go through some tutorials to understand how Rhino works and what some the terminology in Rhino means.

Hi Drew and welcome to the forum and to Rhino. I first started on v2 back in 2000 and of course still find issues with this program but wouldn’t trade it for the world! As David mentioned run through some tutorials and use the help guide its one of the best out there, all the commands have very useful examples.

In your example, as with other modeling software, think in stages of production.
ex: Extrude out the plate first as solid, then extrude your hollow cylinder bosses after. Then booleanunion them into a closed polysurface.

trying to extrude things in wrong order can have varying results. see pic of 4 different ways to extrude the same set of curves, all with different results. The last on the right is the ‘correct’ way of doing the plate and bosses separate then booling them.

Be patient, read the manual and check some tutorials and you will get there. This is the best general cad program for the price IMHO. I have used it to model almost everything out there. Its ability to handle big meshes and tons of complexity have made it my main design app.


Hi guys – thank you so much for the replies – I appreciate it. Attached is a pic of the original exercise I was trying to model, and a copy of the file I just finished. I was able to do it, but I had to extrude the bosses and the bottom plate separately (and moved away from each other in the modelspace), then move them together & do a booleanunion.

The model file kinda shows the steps I took.
practice1 2-12-24.3dm (567.1 KB)

David – your description of the curves in question as “partially coinciding” is a much better way to phrase it than I did – thanks – that’s exactly what I meant. I was hoping there’d be a way in Rhino to select & extrude the circular areas into bosses, and then select the curves that define the outer edges of the plate, along with the circles that defined the outside diameter of the bosses, and then extrude that area to form the plate. But it seems like you can’t do that, and you have to copy the flat sketch, move it, trim the circles into arcs so that there are no “pieces” of curves hanging outside the closed area you create, and extrude the plate area separately, and then combine them together.

Is that pretty much how Rhino works with extruding? Thanks very much for your help.

Also – kinda unrelated, but something I’ve been wondering – is there a way, in shaded mode, to get rid of the lines designating the original edges of separate 3d objects that still show after you booleanunion them? I know they don’t show up in rendered mode, but rendered is much harder to work in than shaded mode. Thanks!

And thanks for the encouragement, Robert. I’ve played around some with Designspark, as mentioned above, and Solidworks, and they’re both seemingly quite different than Rhino in how they handle extrusions.