Unfold Spherical Shape
Kevin Wisher
sheetmetal functions ?
TIA
Kevin Wisher
JM Brun
Turn it into an infinity of faces?
Regards from the 5th dimension.
Brun JM
Kevin Wisher a écrit dans le message <37e07...@news.oaktree.net>...
done2020
speaking? And if you figure that out, you have a shining future in
cartography! Maybe the next release of SWX will include a tesseract or
mobius function. Possibly even a pretzel straightener! All comments
in good fun, Kevin. We ARE engineers here, after all. I'm curious
what your application is. Perhaps a surfacing package and/or FEA can
give you the desired effect. And by the way, if you ask a ProE
salesman, I'm sure he'll tell you that their software can do all of the
above (and below, and laterally; but of course not literally.)
Cordially, Don Eason
In article <7rq1le$boj$1...@front2.grolier.fr>,
Sent via Deja.com http://www.deja.com/
Share what you know. Learn what you don't.
M.B.Stephens
type of work for the stamping industry.
Ray L. Nicoli
I don't know if solidworks will do it, but I feel that Brun's response was a
bit harsh. Has this guy never looked at a map of the earth? You can
"unfold" the world to make a flat map. CAN Solidworks do the same thing?
That is the question.
JM Brun wrote in message <7rq1le$boj$1...@front2.grolier.fr>...
>How in the real world do you unfold a sphere ???
>Turn it into an infinity of faces?
>
>Regards from the 5th dimension.
>
>Brun JM
>
>
>Kevin Wisher a écrit dans le message <37e07...@news.oaktree.net>...
Chris Halasz
'unfold' as mentioned.
--
Bison Sportslights Inc.
15350 E Hinsdale Dr, Unit A
Englewood, CO 80112-4245
303 680 0304 tel
303 680 6462 fax
bi...@rmi.net email
http://www.bisonsportslights.com
M.B.Stephens
mercator projection. If you look at a flat map of the world, the longitude
lines are all evenly spaced. Yet on the globe, the longitude lines start out
together at the north pole, diverge to the equator, and rejoin at the south
pole. Sheetmetal programs assume no real overall stretch, except at the bend.
Here's how to convince yourself. Take a flat map of the world and try to fold
it into a sphere. Alternatively, slice up an old basketball and see how flat
you can make it.
"Ray L. Nicoli" wrote:
> O.K.
JM Brun
Ray L. Nicoli a écrit dans le message <7rr430$eid$1...@paxfeed.eni.net>...
>O.K.
>I don't know if solidworks will do it, but I feel that Brun's response was
a
>bit harsh. Has this guy never looked at a map of the earth?
OK, I admit. Just couldn't resist.
Still, as Done2020 stated, we are Engineers here. It is just common sense
that there are shapes that can NOT be unfolded. Think I did that in school
when I was 12 or 14.
A friend of mine (you know him: Da Vinci) did play around with this
problem, and came out with a bunch of polyhedrons (??? multiple faces,
sphere looking _unfoldable_ solids) or different orders, with even
(regular?) or uneven (irregular?) faces.
I think I remember seeing some of those in Acad. samples drawing.
Anyway, a part of a sphere has NO unfoldable shape. Give me any regularly
cut shape of flexible material, and if it stands the strain, I will turn it
into a part of a sphere.
Now, if you can describe the amount of strain or stress you want to apply to
it,…..
Regards
Brun Jean Marc
Kevin Wisher
developed a plastic part for needs this cloth glued to the part. I was
thinking about offering to produce a cutting die for this if it was
possible. One shape would have to fit around a complete ball. The other
would be half of a cup. Both shapes are .440" radius.
Kevin Wisher
M.B.Stephens
JM Brun
Kevin Wisher a écrit dans le message <37e20...@news.oaktree.net>...
>The material in question would be thin cloth. A new customer that I
>developed a plastic part for needs this cloth glued to the part. I was
>thinking about offering to produce a cutting die for this if it was
>possible. One shape would have to fit around a complete ball. The other
>would be half of a cup. Both shapes are .440" radius.
>
>Kevin Wisher
>
could work.
I fear that with such a small diameter, the production process would not be
simple.
I don't think SW 98+ could do the aproximation. SW99 would be better, but I
have not organized the jump in my office yet.
Regards
Brun JM
Jason Iannuzzi
reason.
After a very extensive search, I found that there are over 20 different ways
to approximate a projected sphere, and each method has some kind of
advantage over the others. It all depends on what is the most important
part to keep accurate.
In the end, I decided there was no real GOOD way to do it, so I came up with
another solution that met my needs in a different manner.
If I can dig up the old url's, I'll post them.
Jason
Kevin Wisher <kwde...@solidmold.com> wrote in message
news:37e07...@news.oaktree.net...
pat
that would be capable of creating a developable surface that could be folded and
unfolded. However, whoever is going to do this needs to have a fair
understanding of surfacing: if the only 3D package they've used is Solidworks
it's unlikely they will. Otherwise you can go thru various calculations and
come up with an approximate flat or just go to the shop and create one based on
whatever criteria you are using. I have used all three approachs for creating
the flats for creating the kits and templates for aerospace layups and if you
have the tool oftentimes the last approach is best. If you are going after mfg
issues as you design it then one of the first two (there are other surfacing
packages out there that can unfold various surfaces I don't remember all the
prices -- Surface Express is $2K)
Pat
billmce
the curvature is in more than one direction the material properties govern
how the shape will deform to the desired shape even if it is infinitesimally
thin.. A surfacing code is not the right tool. You would need an NL FEA code
to account for the elastic/plastic material properties. However, you can get
some insight by exploring and experimenting. I would suggest making a
spherical sector in SWX. You can then project some lines onto the surface of
the sphere. I would put one on the bisector and then some number normal to
the bisector. One along the base as well. You can then measure the length of
the bisector and use that as a projection of the bisector line onto a flat
surface. You can then measure the normals and get some other points on the
edge. You can then fit a spline from the top of the bisector through the
points to the base of the sector. You can then check the length of the 3D
edge and compare it to the length of the approximated 2D edge. What you will
find is that the 3D edge is shorter that the 2D edge. You can forget the
curve and just draw a straight line from the base end point to the top of
the projected bisector line and it will still be longer than the 3D curved
line. Hence, you have to account for the material properties and how they
will drive the shape transformation. What really happens here is that the
edge actually buckles to fit when you curve it up.You ca develop some sort
of empirical method by running a bunch of experiments and finding out what
gets you close enough. If you are doing a composite ply on +-45 to the
bisector line assuming that the bisector length would remain constant would
not be sensible. It would probably get longer with any tension whatsoever as
their is so little stiffness in the ply in that direction.
So for whatever it is worth you can go convince yourself that it just
doesn't work but you may be able to get a workable predictive method for a
set of particular conditions. But I wouldn't get too excited about it - it
will require lots of work and vigilance to keep in the right ball park.
Good luck. Nothing's easy.
Billmce
Pat <p...@san.rr.com> wrote in message news:382CEA54...@san.rr.com...
> > it,...
> >
> > Regards
> >
> > Brun Jean Marc
>
Jason Iannuzzi
following conclusion...
There are numerous approximations of a planar sphere, and each one has an
advantage over the others. It depends on what requirements you have. Some
approximations keep tight tolerances on longitudinal distance, some
latitudinal, etc. etc. etc. There are many many different ways to unfold,
you just have to choose the one that meets your needs.
Jason
pat <p...@san.rr.com> wrote in message news:382CEA54...@san.rr.com...
matt
ago. I think he was using an early mac or something archaic
like that, so the solution wasn't very well accepted. PTC
knew the answer back then too, but people just didn't buy
into the concept of flattening out the globe, because they
thought it was already flat anyway. Plus, no one liked
their haircuts in those days. Still, there's something
about Mercator, spheres and flat that I just can't get out
of my mind.
You don't have to get a bigger hammer to solve what seem
like big problems, although a big hammer might work pretty
well in this case. Try peeling a couple oranges and
thinking about it for a minute or two. Or maybe just take a
mental trip around the globe, using a wall map...
--
Matt
billmce
matt <mlom...@frontiernet.net> wrote in message
news:3834EFB8...@frontiernet.net...
matt
little silly while trying to give a way to solve the
problem. Gerardus Mercator lived during the 16th century
and was responsible for the "Mercator Projection" which
distorts a sphere into a rectangle. The other type of
projection map (the name of which I do not know) is the one
that looks like an orange peel. Neither of these solutions
is faceted.
To approximate a sphere as a truncated icosahedron (soccer
ball), which could then be unfolded, would give a faceted
solution. Try this site as a starting point:
http://www.mathconsult.ch/showroom/unipoly/25.html I have
tried to use SW sheetmetal to unfold a soccer ball. It
doesn't work very well. SW tech support did get a chuckle
out of it, though.
But then, maybe you're just trying to manufacture something,
in which case, I think the best you can do is to cut two
circles out of plate and bang the hell out of them to make
them round. Weld to taste.
--
Matt