Sheet Metal coplanar surfaces will UnFold but not ReFolded

[martinlmarriott]

Hi all,

I am hoping that an AD employee who knows about the Fusion Sheet Metal workspace could comment as to whether this behaviour is a bug or intended behaviour (in which case it is not good).

I attach the file for you to play. - https://a360.co/3PSpsYc

As you will see, it is a very basic Sheet Metal box with corner flanges for screwing together. A very common technique I think you will agree.

I Flange the short sides first.

Then Flange the mounting tabs using the “Bend Position” = Outside.

Then Flange the long sides using the “Bend Position” = Inside.

This gives the inner face of the mounting tabs and the outer face of the long side to be coplanar as expected.

Now as you can see in the Section Analysis, they “appear” to be combined.

Now if you Unfold, then this works. However, it will not Refold.

If I extrude the short side edges a tiny amount before applying the mounting tab Flange so that the two surfaces are not coplanar, then all is good, but in my view, I should not have to do this to get it to work.

It will also Flat Pattern.

The problem could be:-

• The flange operation that produces coplanar surfaces incorrectly joins the two surfaces.
• Whilst the Unfold command can understand that they are not joined, the ReFold command cannot.

My question therefore is…is this a bug?

Thanks in advance.

Martin

[TrippyLighting]

Looks like a bug to me @Phil.E 

[HughesTooling]

I'm actually surprised this unfolds because the flanges have no clearance so Fusion self heals the touching faces.

You can see there's no gap and the 2 faces have become a sold.

If you add a small offset before creating the two long sides it will work. See attached file.

[HughesTooling]

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@martinlmarriott wrote:

Hi all,

My question therefore is…is this a bug?

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Not sure whether it's a bug or just a restriction caused by the modeling kernel, touching faces are joined if they are part of the same body. Has come up several times over the past few years. Maybe there should be an override to shift the flange by a small amount so it's part of the flange feature rather than an extra feature in the timeline.

[martinlmarriott · Accepted solution]

Thanks for your reply but if your read all of my post you will see that I pointed out the "apperent" joined faces and the work around I did myself of offsetting the faces.
However, this workflow is so common and after all, this is largely what setting the Flange to "outside" is for.
Given that both Unfold and Flat Pattern are smart enough to know that those coplanar faces are not (or should not be) joined and are successful, it seems odd to me that ReFold is not similarly smart.

[martinlmarriott]

I agree with you that an extra box in the Flange command to provide an offset would be useful.
Not joining the faces in the first place or making ReFold a bit smarter would be even better.