Need help understanding Sheet metal flange angles

[MCQAZ]

Hody folks,

I am creating a Sheetmetal part where the vertical part tapers to one end and is also kicked in (To the left) from the starting point. I am trying to place a 0.75" flange on the upper edge to facilitate attaching a cover to it. The problem is that when I bend the flange to 90 degree angle. the upper edges will not support the cover because they slope downward towards the center. I can fudge the angle to achieve the required result but would only be guessing. Can you guys help me understand why the 90 degree upper flange is not parallel with the lower 90 degree bend. Any help calculating the correct angel would also be appreciated. I have included screen shots illustrating my problem.

Thanks in advance for any insight on this

[jhackney1972]

Please attach your model.  If you do not know how to attach your Fusion 360 model follow these easy steps. Open the model in Fusion 360, select the File menu, then Export and save as a F3D or F3Z file to your hard drive. Then use the Attachments section, of a forum post, to attach it.

[MCQAZ]

Here it is. Keep in mind that I am learning and using this project as a training aid. With that said I am sure there will be many things that don't make sense to you or that would have been better accomplished another way. Please feel free to critique it though as that is how we learn. Thanks

[jhackney1972]

Add a Construction Plane between two edges to find the needed angle before placing the two flanges.  Model is attached.

[MCQAZ]

That is what I was thinking of as well. Still working trying to figure out how though.

Any thoughts though on why the two 90 degree flanges are not parallel?

I see you came up with an angle of 75.258 degrees and see how you came up with that. But I am trying to wrap my head around why this would not be 90 degrees.

Shouldn't it be? What am I missing?

[jhackney1972]

The angle of the taper caused the edges, where you are trying to add flanges, not to be parallel to each other.  The flanges will be 90 degrees to the respective sides but since the sides are in the same relationship, they will not be parallel.  Note the angle of the faces you are applying the flanges to in the screen capture.

[Warmingup1953]

There will be a 90 Degrees there somewhere just not where you think!