Merging faces when i DONT want it to

[ddt_thompson]

Hi all....I see a lot of posts with people wanting to merge faces, but I'm looking for a way to prevent it. When I extrude or use the flange tool Fusion always seems to merge the faces on the same plane. I can't figure out a way to stop this. I would like the faces to NOT merge so I can grab and manipulate them after the bend/extrude. Am I missing a button somewhere to prevent this behaviour?

[g-andresen]

Hi,

please show this behaviour in a screencast.

günther

[jhackney1972]

If you are using the Bend or Flange tool in sheet metal, you cannot prevent the merging of the faces as that is the purpose of the tool.  On the other hand using an Extrude, you can simply select "New Body" to prevent the merging of the faces.  If you need something else, please clarify your question using a video.

[ddt_thompson]

I hope this video makes sense...i seemed to have not captured the tools, but I was using the flange tool. You can see that it merges the faces. I find this strange because this would never happen in the real world so using this as a modeling program as a design tool prior to manufacturing doesn't work well in this use case. Metal faces don't automatically weld themselves together. I think at a minimum there should be an option to prevent this. My apologies if there is and I'm missing it.

[jhackney1972]

I agree, in real life the sheet metal will not "melt" into the face but in Fusion 360 sheet metal, if the faces touch, they will join.  All you need to do is put a "very" small gap between them to prevent this from happening.

[ddt_thompson]

Well in some scenarios when exactness isn't required leaving a small gap is a workaround. However I think this should be considered a bug (since it is arguably unexpected modeling behavior) or at a minimum a feature request. Unless there is some reason we would want merging faces when using sheet metal? Maybe there is a reason for this that I can't think of. 

[TheCADWhisperer]

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@ddt_thompson wrote:

Well in some scenarios when exactness isn't required…

Maybe there is a reason for this that I can't think of. 

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What sheetmetal manufacturing process are you using that creates exact geometry?

I will wager that if you show me your actual part that I will find that the faces are not merged and that there is a layer of air molecules (or at least elemental atoms) in an at least microscopic (if not visible to un-aided eye inspection) gap between faces. 

[ddt_thompson]

Design tolerances and manufacturing tolerances are different, and adding air gaps to prevent faces from merging is a hack. And yes I AGREE that the actual part would NOT have "merged" faces. That is my complaint...Fusion MERGES the faces when it shouldn't. 

[TheCADWhisperer]

@ddt_thompson 

You cannot manufacture perfect parts.

if you design at “perfect” geometry with faces touching - in manufacturing some features will actually be a little smaller than “perfect” and some will be a little larger.  Without allowance for realistic tolerances the features will collide and perhaps warp.  With unresolved tolerance stack-ups the situation is compounded. Just the facts of real world manufacturing and assembly.

For nearly 30 years I tried to drill this into students heads.  Some got it - others not.

Design tolerances should equate to manufacturing tolerances.

[ddt_thompson]

Yes but you are missing my point. Fusion should allow us to factor in manufacturing tolerances as a FEATURE and not as a "hack" to keep faces from merging....think of the bend radius calculations and how "exact" they are. If they are sweating the exactness of a bend radius then it seems logical to me that they would allow us to control the offsets of other materials touching prior to merging.

And I still can't imagine a scenario when we would want the faces to merge since that never happens in the manufacturing process. But maybe there is a "design only" method that makes the merging desirable?