Again, issues with unbend/rebend

Legend
Legend

I had thought all the issues I had been having with unbending/rebending with lofted flanges were resolved, as ST9 seemed to be the end of the particular errors I was getting where it would unbend but not rebend. But now I'm noticing there is a small significant issue. On this lofted flange which I do an unbend on, then place a cutout and pattern some holes, when I rebend it, at first glance is fine but now I notice is actually cocking the model ever so slightly in one direction. See video and pay close attention to the blue sketch and the metal as I flip between just before the unbend to the rebend. Any suggestions? I did the unbend selecting the all bends option, and on rebend I also selected all bends.

(view in My Videos)

ST9
Windows 7 Professional
Nvidia K2200 & Intel Xeon
"You're doing it wrong"
19 REPLIES

Re: Again, issues with unbend/rebend

Creator
Creator

Have you worked out the issue yet?

 

Can you upload the model?

Edging since V18

Re: Again, issues with unbend/rebend

Legend
Legend

Have not. I just have been reorienting the principal view in my draft to make it symmetrical and level.

 

Uploading the model would require much more than just this model due to the interpart links involved.

ST9
Windows 7 Professional
Nvidia K2200 & Intel Xeon
"You're doing it wrong"

Re: Again, issues with unbend/rebend

Phenom
Phenom

I think there is a simple solution to all of this, but have yet to take the time to request it. 

 

All sheet metal cuts should be normal to the K plane by default. This is not even an option right now.

 

Then the flatten/rebend workflow would not be needed at all.

Re: Again, issues with unbend/rebend

Legend
Legend

Actually, in my case I would still need the unbend/rebend. For I usually use it to make cutouts and hole patterns that will be true round in the flat. Usually on cones.

ST9
Windows 7 Professional
Nvidia K2200 & Intel Xeon
"You're doing it wrong"

Re: Again, issues with unbend/rebend

Phenom
Phenom

That would be the result. 

Normal = perpendicular to the tangent point

K plane = where the metal is neither stretched or compressed...the neutral axis.

 

So a cut normal to the K plane of a circle on any shape would result in a circle in the flat.

 

My motivation behind this applies to many cases. A simple one is when side angles are used on flanges. This would result in a true cham in the flat. The most complex case would be when the cutout is partially overlapping a 3 way corner.

 

That way of cutting should be relativly easy for them to add to the software. And this should be the default when working with any sheet metal cut.

Re: Again, issues with unbend/rebend

Legend
Legend

So but on a cone, how would I even go about drawing the cutout in the first place? When I have to place the cutout a certain distance from the bottom or top of the cone, but looking at it from the side, not on a plane tangent to the cone? Currently what I do is make a rectangular cutout in the cone centered on the intended center of the circular cutout, but much smaller than that intended circle. Doing this lets me, when unbent, determine where to place the circle since it gives me midpoints to work with. I'm sure there is probably better ways to go about this, but I just haven't come up with one at the current time. Any suggestions?

ST9
Windows 7 Professional
Nvidia K2200 & Intel Xeon
"You're doing it wrong"

Re: Again, issues with unbend/rebend

Legend
Legend

Then what would be the result of say a large sheet metal cylider which has holes that are spaced along the bottom of it? I mean that these holes are supposed to be looked at straight on, all of them appearing to be a circle when looking directly at it, but in reality they get stretched more and more elliptical as you get farther from the cylinders center. We do this for placement of parallel pipes. I guess I'm having a hard time wrapping my head around the difference between using a normal cutout and having the cutout perpendicular to the neutral plane. I mean, in the flat shouldn't that give the same result?

ST9
Windows 7 Professional
Nvidia K2200 & Intel Xeon
"You're doing it wrong"

Re: Again, issues with unbend/rebend

Phenom
Phenom

In that case, you would not want that. 

 

My point is that the "normal" cut for sheet metal should be relative to the neutral axis (or surface as it really is), not the top, bottom, or middle. And that 90% of the time, this would be the desired default.

 

Your case with pipes running though a cone would be an exception where you want ellipse cutouts that are outside of the circle considering both sides of the intersection between sheet and pipe.

Re: Again, issues with unbend/rebend

Legend
Legend

I fully agree in that having the normal cut perpendicular to the mid plane of seems crazy when you can't have it to the neutral plane as well.

ST9
Windows 7 Professional
Nvidia K2200 & Intel Xeon
"You're doing it wrong"