sheetmetal

Hi,
To model the transition from rectangular to circular section in a duct
made with sheetmetal I was used to do the following:

I did one blend between one circle divided in 8 parts and one rectangle
with rounded vertexes. Then I converted it to sheetmetal and then to
unfold it. But now in Wildfire2 it does not work as it did in 2001.

Anyone knows how to make it?

 

None of this functionality is different than it was in 2001, some new icons,
maybe, but that's about it. All the same old menu manager crap as before. I take
it that you're getting stuck at trying to unfold or unbend or flat pattern it. I
couldn't do it either. I thought it might be because there was no ripped edge, so
I put one in. Then I noticed that when I tried to do an unbend, there are no bends
~ it's a single walled feature. Could that have something to do with it? While I
know that you ought to be able to flatten this shape out, it is not the typical
tabulated surfaces of ductwork. I wonder what would happen if you created the
blend within sheetmetal. I didn't try that.

David Janes

 

To model the transition from rectangular to circular section ...

Couple of prt's that may help.

http://www.mcadcentral.com/proe/files/streamfile.asp?imageid=985
http://www.mcadcentral.com/proe/files/streamfile.asp?imageid=1207 *


* Note each blend creates single faces vs. creating muliple faces blending curve
chains as a single feature. Whenever I've tried to do something similar using
chains the resulting surfaces will usually have a slight compound curvature
(show Shaded Curvature Analysis) and won't flatten or unbend. [Not that I'm
sure that means anything. I can create similar shapes with VSS, reports 5E-06
curvature and still won't unbend. Things going on I don't quite comprehend or
can't devine from available analysis functions.]

 

I'll have to wait till I get hold of the commercial version to open those files

When I can't figure stuff out with a digital model, I start thinking what the real
thing would be like, how you'd actually make the developable sheetmetal ducting.
Not having any sheetmetal handy, I tried paper. Since there aren't any real bends
in the thing to "unbend", I decided that the basic shape was a truncated cone
(clear enough at the round end), that's been forced into the square shape at the
other end. I did it with paper, trimmed it, flattened it and it came out as I
expected. But, while forcing it into the square shape, I did notice some buckling
in the middle. I wouldn't be surprised it this was happening to the model, that
the model needs some rip or point relief at one end or the other. Or maybe a
Deform Area somewhere. That seems to come up in relation to Blends and
undevelopable geometry.

 

... Or maybe a Deform Area somewhere.

That's true in a lot of cases. I got curious about the VSS quilt that failed
(for no apparent reason). Wrote the quilt out as IGES, imported into a new
file, thickened, converted to SM and flattened. Appears to be a bug (or some
subtle change or "healing" is taking place on import). I'm going to post it to
mcadcentral's bugs and builds group and see if someone will tell me if it works
in newer builds than my M010 WF2.

 

I finally got into the models you gave links to; nice, elegant solutions to all
the questions I had about how you could possibly aviod creating undevelopable
geometry. I especially liked blending 4 points on the circle to 8 on the rounded
rectangle which created planar tripatches and left all the round geometry to the
circle/rounds. So obvious, so simple. Thanks.