help with sheet metal problem

sw2006sp5.1
I've used sheetmetal very little and I'm kind of lost on this part.
I'm trying to make a sheet metal part that looks like this sample surface.
http://briefcase.yahoo.com/bc//lst?.dir=/Docs&.src=bc&.view=
It would be made on a press brake so the inside radius on the bends should
all be .125" and the material would be 0.1".
I tried to do this as a sheet metal loft, but I couldn't seem to control how
the different line segments connected between the two sketches, so I never
got the triangular surface. The following statement was in the help system,
"If the loft preview shows an undesirable loft, re-select or reorder the
sketches to connect different points on the profiles." This seemed like
maybe a relevant concept, but they stopped short of actually revealing how
it's done.
If it is necessary to fudge by cutting a hole (rip, relief,etc) at the sharp
point of the triangle, that would be fine because I'm mostly concerned with
deriving the periphery of the flat pattern. In real life this area is
distorted some anyway.
I'm hoping I can put a large blend/fillet on the edge between Surf2 and
Surf3, so there isn't a visible edge there.
Is a loft the best approach, or do you think shelling out a solid would work
better?
Any ideas would be appreciated.
Thanks, Bill

 

I'm no sheet metal expert. Basically this is what I see. The
triangular surface technically can't be made by bends alone. By bending
those two bends you are actually forming the material ( stretch along the
long edge of the triangle and compression along the edge between surfaces 2
and 3 ). Solidworks does not yet understand forming, only bends.

Here is a way to get around the limitations. Take surfaces 1-3 and knit
them ( exclude the triangular surface ). Radius the edge between surafes 2
and 3. Thicken the surface. Insert-sheet metal-bends. This converts it
into sheet metal that can be flattened. There is a warning given in the
bends, but its not significant to the outcome. This will give you a starting
point for your periphery.

To take into account for the stretch/compression thats occuring. Look
at the flat condition, with the triangle's wedge on your left. The lower
left corner of the part, and the lower left corner of the wedge won't be in
the correct location. You'll have to form a part, measure it, then adjust
them to bring your part to within tolerance.

The alternative is finding someone with forming software and have them
do your flat pattern.

 

Try it now.
I'm surprised though, that Brian could open it before.
Hard to figure.

Thanks, Bill

 

It appears that sbcglobal is even more hosed than usual this evening. Half
the times I've tried, I can't even access that folder myself.

I think I know a partial solution already, i.e. the need for the addition of
a rip to avoid distortion/forming which would have occurred, as Brian said.
I still don't know what's the best strategy for the design, but as I think
more about it, I can probably do everything with sketched bends instead of
lofts.

Thanks, Bill

 

yes, you need some relief.


https://home.comcast.net/~kennethbarrentine/TestDart3.zip

 

The bend that makes the lower edge of the triangle is actually being done
with the press ram tilted, and they of course get some distortion (tolerable
for what they're doing) in the spot where you put the relief cut. They can't
do a regular bend because the material continues further than is shown on
the sample. With ram tilt (there may be better lingo for this), the
triangle face is twisted somewhat, and I'm assuming that swx can't resolve
something like that as sheetmetal.
Do you think the design I've shown is about the only way to approximate that
type of bend, and would it produce a reasonably accurate flat pattern? I
realize that some relief cuts, etc will need to be dealt with manually for
programming the cutter.
I hope these questions aren't too dumb, but this is one of my first projects
involving sheet metal.

Thanks, Bill

 

you're close. you could tweak the extension (surf3) a bit to remove that
blend line (just a visual thing).

also, you could scale (or not) the part down somewhat and do some setup
parts. this should give some idea as to the corrections you will need to
apply for final flat. this is almost a must do.

<snip>

what you're doing here is very similar to a cross brake. mild "x" shape
bends across a panel to add stiffness. sw can't do this either.

you couldn't have picked a better part to start with!

 

I'll be able to tweak the flat part, I just didn't want to be embarrassly
far off the mark the first time through.
I guess I'm trying to limit second guessing of my modeling technique, later
on. :~)
Thanks a lot,
Bill