Surface Stitching - Confusion.

[daveK39DU]

Hi All,

I have a constant problem with surface stitching.  To illustrate I created the following simple scenario.  One cylinder surface and one planar surface fully intersecting.  Now I fully understand that because there are no edges at the intersection, these two surfaces cannot be stitched. That's all good.

So in order to create edges, I split the bodies using the other body as the tool.  Therefore edges must be coincidental right?  I now have 4 bodies and if I stitch all 4 bodies (inner plane, outer plane, upper cylinder, lower cylinder, the will stitch into a single surface body. (because there are edges and they are all coincidental.) . Still all good.

Please bear with me (I'm getting to the crux of the issue).  If I first stitch the upper part of the cylinder to the outer part of the plane and then stitch the lower part of the cylinder to the inner part of the plane, I now have 2 surface bodies with edges coincidental at the circular edge.   If I now try to stitch these two bodies together, they will not stitch!

 

The edges haven't changed (As far as I know).  So can anyone tell me why these two bodies won't stitch?  I encounter this happening on a regular basis.  Sometimes it works, many times it doesn't and this really has me tearing (what's left of) my hair out!  My suspicion is that the previous stitch slightly altered the edges so that subsequent stitches won't work (but that's just my guess).

Thanks in advance for any input here.

Best wishes,

Dave.

SO

[davebYYPCU]

Because you Stitched in 2 operations, depending on tolerance setting, each stitch operation, has welded edges together, and they may no longer be coincident, not visible to the human eye but now inconsistent.

Hopefully this is demo, and not a real design, as I have no idea why you would want to do that.

Might help....

[jhackney1972]

You only want to use the Stitch command once and select all three surface bodies.  Two surface bodies come from using the Split Body command on the tube with the flat surface as the splitting tool and the other body is the flat surface.  Screencast will show how.

[daveK39DU]

Thanks both of you for your input.  I understand that if I do consecutive stitch operations on the same edges, I run the risk of those edges not being perfectly coincidental.   My real worldreason for asking the question is illustrated by a screencast. For some reason the forums won't let me embed it hopefully, you can see it here;

https://autode.sk/3OSjeFy

Before you ask why I am making this out of pure surfaces, the answer is for thin wall 3d printing.  Any solid body will print  as at least two walls and for lightweight flying model aircraft only one wall is desirable.  Anyway, you can see here that I create a patch out of an intersection with the body and then split the main body using the patch as a tool.  Therefore the edges have to be coincidental.  But when I stitch the 3 bodies together only two stitch?  If I try to follow up with a second stitch, the second body will not stitch for the reason both of you mentioned.

Maybe my workflow is wrong here?  How should I be inserting a patch like this inside the body?

Thanks again,

Dave.

[jhackney1972]

If they use a surface to split a surface body the resulting edges will be inline, unless you do a following operation to move them.  Please attach your model and let the Forum users take a look at your exact model.  If you do not know how to attach your Fusion 360 model follow these easy steps. Open the model in Fusion 360, select the File menu, then Export and save as a F3D or F3Z file to your hard drive. Then use the Attachments section, of a forum post, to attach it.

[davebYYPCU]

Make a second patch, join one to each larger body.

Which Slicer allows you to print a surface body?

Might help....

[TrippyLighting]

I am not sure I understand. Why would you even need to split the bodies?

[daveK39DU]

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@davebYYPCU wrote:

Make a second patch, join one to each larger body.

Which Slicer allows you to print a surface body?

Might help....

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Thanks.  I tried that but it will not let me join the two bodies together.

Cura has a surface mode under "Special Modes".  This allows you to print pure surfaces as single wall prints.

Regards

Dave.

[daveK39DU]

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@TrippyLighting wrote:

I am not sure I understand. Why would you even need to split the bodies?

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Because without splitting the body first, there would be no edges to stitch the patch to.

Regards,

Dave.

[daveK39DU]

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@jhackney1972 wrote:

Please attach your model and let the Forum users take a look at your exact model.

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Thanks John,

Please see the attached. I got rid of the fluff to leave the main issue.  You can see three surface bodies.  I start by creating the patch based on intersection with the main body. I then split the main body using the patch as the tool.  Any two bodies will stitch, therefore the edges must be coincidental. But not all three at the same time.  That's the bit I fail to understand.

Regards,

Dave.

[TrippyLighting]

@davebYYPCU The example that was provided was a cylindrical surface body that fully intersected a planar surface.

There is not need to stich anything so there's no need to split anything. No ?

I was under the impression that most slicers would take care of this automatically

[TrippyLighting · Accepted solution]

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@daveK39DU wrote:

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Any two bodies will stitch, therefore the edges must be coincidental. But not all three at the same time.  That's the bit I fail to understand.

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Because that would not result in a manifold!

If you want to create one cohesive solid body, then you'll likely need to thicken the individual surfaces and use the Combine tool.

[daveK39DU]

Thank You Peter.  Now I understand! Although I've been using fusion quite a while.  I'm not a professional and often don't understand the terminology.  So I read up about manifolds.  The best description I found was this "A non-manifold geometry is a 3D shape that cannot be unfolded into a 2D surface with all its normals pointing the same direction".  Now the lightbulb has come on and I totally understand my problem and why my three bodies wont stitch.

Thank you for answering this for me.