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Boolean Non-Manifold Issue
michael_pallone
Member Posts: 7 ✭
Hello all,
I'm new to CAD modeling and I use it mainly to design stuff for 3D printing. First, please pardon my ignorance with OnShape. I've learned from just playing around and watching YouTube videos, lol. I'm running into an issue on a recent model and I'm not sure why or how to resolve it. I've searched for answers but no luck. I'm hoping this wonderful community can help. I have made a short video and have attached it via YouTube link below. I clicked on all sketch and extrusion elements so you can see what I am starting with, and then I proceeded to sketch a new triangular shape and pattern it around in a circle. However, when I try to extrude it up, I get a regeneration error that states that "boolean operation would result in non-manifold body." Also, I have the free version of OnShape and I know all of my models are public. So, if it's easier for you guys to directly access my model in order to help me figure this out, please feel free! Link is provided below for that. Any and all help is greatly appreciated! Thanks!
Michael
Link to model: https://cad.onshape.com/documents/c1c61fd4c9b90f7d41265469/w/75de42aa77755d7b6e754517/e/2ec2f57331102fea2d6bcc5c
Comments
Your video is private. But the the link tells the story. Non-manifold means zero thickness. All of those wedges come together at the center to form zero thickness geometry. One solution would be to put a tiny cylinder in the middle where they meet. You can make it the same size as your printer filament, so no one will ever know.
@Matt_Shields Thank you so much!
Sorry about the video. I guess I forgot to change the visibility, lol. I fixed it just now though.
Anyway, thank you for your help! OK, so non-manifold means zero thickness, got it. I can see where that is a bad thing, haha! And your idea to put a tiny cylinder in the middle was a great idea and worked like a charm! I was even able to make it as small as 1 mm and it still worked. And we'll never see that on the actual 3D print. However, this leads me to another problem… I wanted all the wedges to have a 1 mm fillet all around the perimeter of their top face and it won't let me do that. It says it did not generate due to "overlapping fillets." I'm guessing this overlap occurs in the center at that tiny cylinder. So I tried making the cylinder bigger to see if that would help, and it did, but not until I made the center cylinder 20 mm in diameter. It looks ok but it wasn't really the design look I was going for.
Prior to this, my workaround was to sketch one wedge, extrude it up 1 mm, add a 1 mm fillet to its top face, and then use the circular pattern tool (using "part pattern" from the drop down) with the center point as a mate connector for the "axis of pattern." It let me do that with no issues. But it also made my model 16 individual parts, lol, which I wasn't a fan of. But then I remembered reading something about the Boolean tool being able to combine separate parts into one. So I tried that and it worked! Not sure if that's cheating, haha! Again, I am still very new to all of this and mostly self-taught via trial and error (and YouTube).
But I did want to understand why I was originally getting that "non-manifold body" error so that I can try to avoid it in the future. The new fillet issue is a separate thing and I kinda understand why that is happening. (If you do have any solution ideas for that though, I'm all ears, lol.) But the original issue was confusing me and I'm still not fully clear on why there was zero thickness geometry at the center. I would think that all the 1 mm extruded wedges touching at their tips in the center would be acceptable, meaning no gaps. I'm trying to visualize the zero thickness geometry and I'm struggling. Is there any way you could explain it further that might help me understand it a little better (if possible)? Hope I'm not asking too much, lol. And thanks a ton either way good sir. Very much appreciated.
There are a few ways I hear non-manifold described. Different people find different definitions more helpful. They include "geometry that cannont exist in the real world" or "geomery where a single edge is shared by more than two faces" or "surfaces meeting at a single point" or "a 3D shape that cannot be unfoled into a 3D surface with all of its normals pointing in the same direction."
As for the fillet, you could add the fillet before the little cylinder. I got it to pattern as a face pattern.
Yet another option would be to just leave a little circle open to avoid zero thickness issues. that circle is .5mm dia in this perspective image.
@Matt_Shields Thanks so much for the follow up. Those extra definitions definitely help me understand this issue more now. Particularly the statement "geometry where a single edge is shared by more than two faces" seems to fit this particular issue. And yes, adding the fillet before the little cylinder is a great solution - much appreciated! It's funny how just changing the order that you do things in OnShape (and CAD in general) can yield very different results, lol. Thanks again for all your help. I am truly grateful.
@MDesign This is another great solution that I didn't think of - thank you! So you just sketched the little circle and did a "remove" extrude, is that right?
Not sure I remember doing an extrude remove. Think I just didn't include it in the original extrude.