increasing .iges / .step tolerance settings on export?

[thoreaubakker]

I've been struggling with shelling complex geometry, and heard about a trick over on the Inventor forum:

@johnsonshiue described how by exporting an iges file with higher tollerance (.0001?) and re-importing it, it's sometimes possible to get a thicker shell (ie. because the geometry has been 'glued' or welded or such on that export).

Can anyone help me find if there are any such settings in Fusion 360? I've looked in settings / preferences, but haven't been able to find options on export.

[thoreaubakker]

p.s. here are Jon's instructions for the Inventor trick:

"1) Import the SAT file to Inventor.

2) Export the solid as IGES (Solid, 143 Bounded, Analytical, and Spline tolerance = 0.0001mm).

3) Import the IGES file back to Inventor."

Is it possible to export an IGES, 143 Bounded, Analytical with a spline tolerance of .0001mm? All of online searches are bringing up nothing.

[TrippyLighting]

Applying "tricks" without analyzing the root cause is educational because in most cases is does not work until the root causes is identified 😉

Most of the time, meddling with these tolerances is not advisable and I am not aware of such a setting in Fusion 360.

If you can post a specific example I can assist you further.

[thoreaubakker]

Hey @TrippyLighting 
U Bet!

I'm struggling to get shells of workable thicknesses, on complex geometry.
And, lol, before you warn me, I can quote you:

"In general if you have to use the word "complex" and "shell" in one sentence then that already indicates the problem." - Trippy Lightning 2018 

The challenge I'm having today is representative of the workflow I'm trying to figure out.
I have a roughly 40mm diameter object, and would like to hollow it (ideally not in MeshMixer) to print on my little hobby resin printer. However, I can't any shell at the current size bigger than .2mm. Ideally I would have 2mm, not .2

Same challenge applies to an object 5x the size, where I would want a 5-10mm shell, but am only able to get 1 or 2mm. I understand offsetting early in T-Splines would be desirable, but for now I'm trying to figure out solutions for the current workflow.

The 'trick' I was talking about seems intriguing, so I would love to try it (if Fusion offers those export options).

[TrippyLighting]

Can you share the model ?

[thoreaubakker]

Sure thing. Attached is a password protected .zip with the Fusion360 file and a step export. (PMing you password).

Just for context: I don't really need this modeled shelled per se, it's more about getting a good workflow. I know complex geo and shell aren't very compatible, but it's funny how it's so close. Like I can only get a '.3' shell here which is basically unusable as that's too fragile for the resin printer. If I just had a 1mm shell even (at this scale) it would be fine. So close but so far.

Still hoping someone will chime in regarding the original question regarding the 'trick'.

[thoreaubakker]

hey @TrippyLighting  did you ever get around to downloading the file?

[TrippyLighting]

Oops... yes, I did actually spend quite a bit of time with it.

In general you'll have problems shelling models that are created by interested/combined T-Spline models.

You'll probably have to work with this on an individual surface level by offsetting and trimming individual surfaces in order to get this shelled properly.

Aside from that, you modeling style could use a bit of general cleaning up 😉

E.g. mode in the right scale from the beginning.