Stitch is modifying the round shape below where the two pieces should be stitched together. First pic shows the unstitched correct shape. Second pic shows the only edges to be stitched highlighted green. Third pic shows the stitched shape with unwanted added features highlighted in red. Unstitching everything and stitching everything again causes the same, but slightly smaller, unwanted features to be added.
How do i stitch these together without the unwanted features being added?
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John Hackney, Retired
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You had some pretty grubby surfaces around the top of the rounded part going into the upper shape so I replaced them. I went ahead and turned it into a solid. You can add any fillets of refinements you desire. Model attached.
By the way, I would recommend you turn on Capture Design History to make your use of Fusion 360 easier and give you a better understanding what is going on.
Edit: You may want to play around with the final Loft in the timeline to get different transition effects.
John Hackney, Retired
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@grahmart wrote:
Thanks for trying however the shape was there for a reason. The software should be able to stitch these edges without modifying other edges or adding unwanted features.
Agreed. However, the model geometry is far from ideal and not modeled properly.
That also applies to @jhackney1972's model. He should enable the "Keep tangent edges" option as it creates better geometry.
@grahmart Are you going to mill this punch?
Won't it end up more like this?
Mark Hughes
Owner, Hughes Tooling
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I believe that what you are seeing here are just graphics effects, but I have not been able to prove it. That is, the geometry may be OK, but the graphics representation has these extra triangles in it (that is one clue, that the apparent glitches are triangle-shaped). I hope to keep looking into this. However, the other advice by @HughesTooling , @TheCADWhisperer , @TrippyLighting , @jhackney1972 are valuable, as well. Higher quality surfaces will always result in better outcomes.
Using the boundary fill feature creates a solid body without any "extra" features.
That could mean something is not quite right with the stitch feature.
I tried lowering the stitch tolerance, but that did not make any difference.
@TheCADWhisperer is correct. Looking at the geometry before the stitch, it is already very bad. It is just a bit of luck that the surfaces don't get drawn differently. Here is a view of the surface before the stitch in our modeling kernel tool. The yellow circles indicate a "tolerant vertex". The size of the circle indicates how big that tolerance is. That means, the location of that vertex can be anywhere in that circle and still be considered the same surface.
after the stitch, those vertices still have the same tolerance, but are just drawn in a slightly different place in the sphere of tolerance for that vertex:
So, the surfaces were bad before the stitch, and they are still bad after.
@TheCADWhisperer will have to answer how he did it. But, my guess is that he deleted and re-created the bad surfaces (no timeline, so it is hard to tell).
"The yellow circled vertices are unmodified from the supplied CAD and are simply curved surfaces meeting"
That is the root of the problem. What format of CAD design was imported here? Some modelers are very imprecise in their geometry. Fusion cannot repair bad geometry. If you didn't have a problem here, you would likely have had a problem later.
I understand your concern. Unfortunately, Fusion does not expose the body checking capability which exists in the modeling kernel to the user, partly because the errors are of the form: " CKID_COED_PCU_POS_INCONS (c234 @00000000021D34A8) pcurve location != coedge location", and trying to explain those in terms that would be meaningful to customers would be a challenge. Measure does not indicate the problems.
No dispute with that. I agree that this is a missing area in Fusion. We should have body checking. As to what you should do: In this case, you should re-design these surfaces. There are several suggestions in this thread. In general, I guess the best we can say is: If you see geometry exhibiting these sorts of bizarre behavior, assume that the geometry might be bad, and think about other ways to model it. If the bad geometry was created from native Fusion operations, I would say that is a bug (though I do know operations - Boundary Patch, in particular, can sometimes generate not-so-great geometry). But, especially if you use imported geometry, your radar should be on for bad geometry.
