topic Re: Having trouble with the shell feature in Fusion Support Forum

Having trouble with the shell feature

alexsandrapontonio — Fri, 23 Oct 2020 00:19:21 GMT

Fusion can't compute the internal shell feature. Error: The operation would cause a large topology change.
Try adjusting the values or changing the input geometry.

I had previously had success on a slightly different shaped model (of the same thing) but needed to add some shape tweaks. Retracing my steps, I am now without success.

I have tried a few workarounds:
- Patching in sections to create the solid (stiched)
- Using the outer surface with the thicken command instead of shelling

Hoping someone might be able to point me in the direction of some common errors for this function so that I can problem-solve.

Thanks!

Re: Having trouble with the shell feature

jeff_strater — Fri, 23 Oct 2020 00:48:46 GMT

this is likely caused by some area of high curvature in your body. If the curvature is too high, the offset will intersect with itself, and that will cause the shell to fail. But, that's only a guess, unless you're willing to share the model here.

Re: Having trouble with the shell feature

alexsandrapontonio — Fri, 23 Oct 2020 00:50:45 GMT

Thanks for the speedy reply. Is there any way to share a single body rather than the whole assembly?

Re: Having trouble with the shell feature

jeff_strater — Fri, 23 Oct 2020 02:07:18 GMT

there are a couple of ways to do that. One way is to save a copy of the design, open it, and delete everything else from the model, save and export that as an F3D. If the body is in a separate component, you can select the component and choose Save Copy As of just that component

Re: Having trouble with the shell feature

alexsandrapontonio — Fri, 23 Oct 2020 02:39:58 GMT

Wow, love this. First time reaching out to the online community. I have been sifting through google for so long trying to solve- really makes a difference being able to put it to a crowd. Appreciate it.

I have uploaded the previous (successful) attempt- slightly different model, a bit less complex. And the problematic one, which I cannot even get to stitch into a solid at the moment (although it was before).

Re: Having trouble with the shell feature

jeff_strater — Fri, 23 Oct 2020 03:02:46 GMT

@alexsandrapontonio - this community, is, indeed, a great place to get help.

Thanks for the model. A few comments here:

You don't need to put the patch on the bottom, then stitch it to a solid, then shell it. That surface itself has some problems:

instead, get rid of that face totally, then just Thicken the rest of it. The results would be the same, if that were successful.
however, that approach has a problem, primarily because of the raised text, I think:
when I look at the "successful" version, you can see that the inside faces do not have an offset of that text:

do you remember how you were able to achieve that?

Re: Having trouble with the shell feature

alexsandrapontonio — Fri, 23 Oct 2020 03:24:51 GMT

Thanks for the suggestion- I had previously tried removing the text as a workaround with no luck, and also tried adding thickness (rather than shelling).

Following your advice, I tried again without success.

However, you inspired me to consider my changing my work order and I have finally after many hours found the fix!

Remove text > Shell solid without side cuts > Apply side cuts.

Thanks again!

@jeff_strater

Re: Having trouble with the shell feature

hiagomtx — Thu, 16 Jan 2025 11:12:11 GMT

When the body is symmetric, it can work if you split the body and do the shell on each half separately. Afterward, you can just remove the middle part and join the two halves.

Re: Having trouble with the shell feature

TrippyLighting — Thu, 16 Jan 2025 12:34:06 GMT

In the vast majority of cases, shelling problems are a result of improper or inaccurate modeling techniques. Dumbed down models without a timeline do not allow us to assess what modeling techniques are used, although in this case, that bottom face was likely created using the patch tool in the surface tab, which is completely the wrong tool for this.

I'd be happy to provide direction on proper modeling techniques to use, but without a design that includes a timeline I am unable to do so.

If you are using a paid subscription, you can PM a link to the design from the data panel.

Disclaimer: I am not an Autodesk Employee. I have no interest in your IP other than helping with the modeling problem at hand.