sheet metal forming pressures
 

I am interested in forming some shallow rectangular bowls from 0.040"
copper. Bowls would be about 1/2" deep and 6" square. I need a press
of some sort to do this, one possibility would be a fly press but I
don't know how big a press I'm going to need. Does anybody have a
formula for the press force needed for forming this sort of thing. Note
that I don't need to cut the copper, that will be done in a separate
operation using a plasma torch, I just need to press them into a
rectangular bowl shape. Thanks for any help you can give.

--
--Steve

"It must not be forgotten that it is especially dangerous
to enslave men in the minor details of life." Alexis de Tocqueville

sheet metal forming pressures
 

"Steve Schlaifer" wrote in message
e.org...
I am interested in forming some shallow rectangular bowls from 0.040"
copper. Bowls would be about 1/2" deep and 6" square. I need a press
of some sort to do this, one possibility would be a fly press but I
don't know how big a press I'm going to need. Does anybody have a
formula for the press force needed for forming this sort of thing. Note
that I don't need to cut the copper, that will be done in a separate
operation using a plasma torch, I just need to press them into a
rectangular bowl shape. Thanks for any help you can give.

--
--Steve


This isn't really a forming op, it's drawing and it's a bitch. GFL if you
think this is going to be cheap. You'd be better off constructing
these...unless you need thousands and they sell for a lot!
"It must not be forgotten that it is especially dangerous
to enslave men in the minor details of life." Alexis de Tocqueville

sheet metal forming pressures
 

On Sep 17, 4:35 am, Steve Schlaifer wrote:
Does anybody have a
formula for the press force needed for forming this sort of thing. Thanks for any help you can give.

--
--Steve
I do not have a clue, but if I were doing this, I would put a pressure
gage on a hydraulic jack and kludge up a way to use the jack to form
the copper. That would give me the actual force needed. I always
choose a measurement over a formula.

Dan

sheet metal forming pressures
 

On Mon, 17 Sep 2007 03:35:18 GMT, Steve Schlaifer
wrote:

I am interested in forming some shallow rectangular bowls from 0.040"
copper. Bowls would be about 1/2" deep and 6" square. I need a press
of some sort to do this, one possibility would be a fly press but I
don't know how big a press I'm going to need. Does anybody have a
formula for the press force needed for forming this sort of thing. Note
that I don't need to cut the copper, that will be done in a separate
operation using a plasma torch, I just need to press them into a
rectangular bowl shape. Thanks for any help you can give.
===========
You may want to consider urethane forming dies.
see
http://www.urethanetooling.com/sales1.htm
http://www.urethanetooling.com/uteccati.pdf
http://www.ganoksin.com/borisat/nena...ess-safety.htm

commercial presses, materials and operations
http://www.beckwoodpress.com/press/a...ion/padforming
http://www.polyprod.com/customtooling.html
http://www.polyprod.com/urethane-sheets.html



Given the material and production volume you can cumshaw up an
adequate manual hydraulic press using a bottle jack, short
sections of channel iron and some all-thread.

With your low production quantities a hardwood form such as maple
should be adequate. The only question is should the form be the
male or female side of the die. Any of our readers have a
suggestion? Any suggestions for the urethane pad such as sources
and durometer? Anyone successfully cast a short run die [male or
female] from the prototype?


Unka' George [George McDuffee]
============
Merchants have no country.
The mere spot they stand on
does not constitute so strong an attachment
as that from which they draw their gains.

Thomas Jefferson (1743-1826),
U.S. president. Letter, 17 March 1814.

sheet metal forming pressures
 

On Sep 16, 11:35 pm, Steve Schlaifer
wrote:
I am interested in forming some shallow rectangular bowls from 0.040"
copper. Bowls would be about 1/2" deep and 6" square. I need a press
of some sort to do this, one possibility would be a fly press but I
don't know how big a press I'm going to need. Does anybody have a
formula for the press force needed for forming this sort of thing. Note
that I don't need to cut the copper, that will be done in a separate
operation using a plasma torch, I just need to press them into a
rectangular bowl shape. Thanks for any help you can give.

Draw die construction is pretty simple. Making the thing work can be
very tough, depending on your requirements.

What kind of rad do you want on your part? The smaller the rad, the
tougher the draw. 1/2" would be simplest.

What about vertical walls? The closer to 90º you get, the more
difficult.

Make sure to polish all your rads until you can see your face in
them... Seriously. Start with 120g sand paper, and work your way down
to at least 400, if not 600. Get rid of deep gouges left by the
coarser paper.

As for your drawing force (pressure requires an area - you're
interested in total force required), I can't recommend a minimum. More
is always OK. Not enough is bad. You'll likely have a tougher time
with a press based on a simply hydraulic jack. Drawing should be
completed in one continuous stroke. Once the material stops moving,
its hardness increases and it becomes more difficult to continue.

0.040" is not thin material by press tooling standards. You're
probably looking at 50 tons or more to get anywhere. I can't even say
that'll be enough.

How many parts do you need? Does it have to be beautiful, or can you
tolerate wrinkles and thinning? Does the "floor" of the shell have to
be really flat, or does it matter? Are you going to be building/
tweaking the tooling, or are you going to pay someone who knows what
they're doing?

If you're pretty liberal about your requirements, you can probably
hack together a functional tool. If you're picky and this is a
sellable product, you're likely better to farm it out.

Regards,

Robin

sheet metal forming pressures
 

On 2007-09-18, Robin S. wrote:
On Sep 16, 11:35 pm, Steve Schlaifer
wrote:
I am interested in forming some shallow rectangular bowls from 0.040"
copper. Bowls would be about 1/2" deep and 6" square. I need a press
of some sort to do this, one possibility would be a fly press but I
don't know how big a press I'm going to need. Does anybody have a
formula for the press force needed for forming this sort of thing. Note
that I don't need to cut the copper, that will be done in a separate
operation using a plasma torch, I just need to press them into a
rectangular bowl shape. Thanks for any help you can give.

Draw die construction is pretty simple. Making the thing work can be
very tough, depending on your requirements.

What kind of rad do you want on your part? The smaller the rad, the
tougher the draw. 1/2" would be simplest.

Actually, I misstated the requirements above, these are about 1/4" deep
with a 1/4" radius curve.

What about vertical walls? The closer to 90º you get, the more
difficult.

There are no walls as such, the edge ends at the end of the curve.

Make sure to polish all your rads until you can see your face in
them... Seriously. Start with 120g sand paper, and work your way down
to at least 400, if not 600. Get rid of deep gouges left by the
coarser paper.

Good advice, my mold maker friend said essentially the same thing.

As for your drawing force (pressure requires an area - you're
interested in total force required), I can't recommend a minimum. More
is always OK. Not enough is bad. You'll likely have a tougher time
with a press based on a simply hydraulic jack. Drawing should be
completed in one continuous stroke. Once the material stops moving,
its hardness increases and it becomes more difficult to continue.

0.040" is not thin material by press tooling standards. You're
probably looking at 50 tons or more to get anywhere. I can't even say
that'll be enough.

That'll be more of a problem, 50 ton presses are pretty pricy.

How many parts do you need?

Limited runs of a dozen or so at a time but hopefully lots of these
over time.

Does it have to be beautiful, or can you
tolerate wrinkles and thinning? Does the "floor" of the shell have to
be really flat, or does it matter?

No wrinkles or thinning, floor needs to be flat.

Are you going to be building/
tweaking the tooling, or are you going to pay someone who knows what
they're doing?

Hoped to do it myself with help from my friend(s).

If you're pretty liberal about your requirements, you can probably
hack together a functional tool. If you're picky and this is a
sellable product, you're likely better to farm it out.

Thaks for the advice, I can get these from a vendor but was hoping to
start making them myself. They are a sellable product so they have to
be pretty good quality.

--
--Steve

"It must not be forgotten that it is especially dangerous
to enslave men in the minor details of life." Alexis de Tocqueville