Hi all, I just took a two day workshop sponsored by SNAG that
introduced the new Bonny Doon 50 ton press and its deep draw tooling.
The press was designed by Phil Poirier and Lee Marshall, and our class
of 12 were the first guinea pigs to have a go with the thing. Speaking
for all present, we were Astounded, Amazed, Delighted, Awed, and
Ecstatic. I, personally, will never forget what I saw this tool do.
The possibilities are hugely exciting!
Before I get totally carried away, I would refer you to Phil
Poirier’s excellent web site [www.poirierstudio.com/gold – look in
the “shop talk” section] to see at the detailed photographs of the
process as he was using it to form 6" diameter discs on his 20 ton
press. That task was a bit much for the smaller press, so Lee Marshall
built a bigger one, with tooling to handle really large diameters of
16g metal. In a week or so there will be photographs on Phil’s site
and on Lee’s site [www.bonnydoonengineering.com] of what we did at the
workshop, including the specifics of the dies, the doming tools, the
press structure, and the vessels we produced – all 70 or 80 of them!
The technology is not new; the same kind of tooling has been used
industrially to form stainless steel in the 1920s and '30s. But as
far as Phil could determine, no one had ever applied it to nonferrous
metals in quite this way before. The basic idea behind deep draw
forming is to push flat piece of metal through a die opening [ours
were all circular] with a second die machined to fit exactly through
that opening with only the thickness of the metal as clearance. For
instance, for an 18g disc, that would be a 1mm of clearance all the
way around the pushing die. The metal is gathered and compressed by
this process, so it is truly raising [as opposed to sinking, where the
metal is stretched and thinned]. After being pressed through each die
opening, the metal is annealed, cleaned, and then centered on a
smaller pushing die and the process is repeated. It is possible to
raise 10" high cylinders 4" in diameter from 12" discs [18g copper] in
about an hour, with much of the time being taken up by pickling after
annealing.
In the workshop we were introduced to the process on three different
scales. The smallest was a set of tools that formed cylinders from 3"
diameter discs using the 20 press. This is a terrific way to make
seamless tubing and flat seamless ring stock. As an enamellist, I am
elated at the possibility of creating small boxes and large beads in
copper and fine silver without having to worry about seams that will
darken or fail in the kiln. The cylinders formed from mokume gane
were just exquisite. You can also form niobium and then anodize it.
The next size of tooling transformed 6" diameter discs into pre-forms
for goblets or small vessels; this worked in the 50 ton press. The
vessels could be either flat bottomed or domed to a hemisphere. In
the second case, there is still a great deal of shaping to be done by
bouging and planishing over conventional mushroom stakes in order to
make the doming uniform and symmetrical. The pressing of these 6"
discs was perhaps the most miraculous to watch. The first step crammed
the disc through the opening to produce a shallow [about 2" high]
flat-bottomed vessel. After annealing, the vessel is inverted over a
hollow steel cylinder about 1/2" thick with a radius on its upper
edge. A second cylinder is positioned in the center, and then pressed
down into the larger cylinder. Yes, this means turning the metal
completely inside-out! [The first time this happened we broke into
cheers and spontaneous wild applause. WOW!] The metal grips the larger
cylinder and is slowly pressed down into the smaller diameter, with
the last 1/2" or so flaring into a wonderful flange before being
squished the rest of the way. One can stop at various points in that
flare to create extremely interesting edge effects. The third and
remaining pressings do not turn the metal inside-out; they just
condense it into a series of steel cylindrical dies that decrease in
diameter. They made a vessel that was about 1.5" in diameter and over
5" tall.
The largest set of tools was made to handle 12" discs of 16g metal.
Since we only had 18g, the clearance between the dies was a bit
loose. This allows wrinkles to form on the upper edges of the vessels,
and these wrinkles would be altered and enhanced with each additional
pressing. We discovered that varying the initial shape of the flat
metal made an enormous difference. For example, a 12" diameter copper
circle would make a cylinder about 6" high after 3 pressings; a 12"
square with the corners rounded to a 3" radius would rise nearly 30%
higher in the same number of pressings.
With a dozen metalsmiths working at a frenzied pace, their
imaginations zooming along at lightspeed, we got an enormous amount of
variation in all three sizes of vessels. The kind of metal, the
initial shape of the sheet, the degree to which it was annealed, and
whether or not one worked on or off center all had dramatic effects on
the outcome. One could also do step raising the way one does step
rolling with a mill, pressing only part way in before backing out and
moving to the next smaller die. By 3:30 on the second day, we had
nearly 100 vessels of various sizes, and the variety of shapes was
truly astonishing. All of these shapes were considered pre-forms,
points of departure for additional shaping by bouging and planishing.
With the hardest and most time-consuming part of the raising done that
quickly and without strain to hands, wrists, shoulders, and back, we
can devote more energy and time to making the vessels into unique and
unusual forms, as well as to complex surface embellishment techniques
such as cloisonne enamel, chasing, and repoussage.
Several of the people in this class had injuries that prevent them
from raising in the traditional manner. I have to be extremely
careful, too, because of a history of tendonitis in my forearms. This
kind of tool will allow us to work again on holloware, something we
had all missed very much when we could no longer do the work without
pain. I am thrilled by the possibilities!
There will be another workshop on deep draw forming this coming
weekend at Valentin Yotkov’s studio in Brooklyn. He has purchased this
press and will be teaching the technique. There will be other
workshops soon, and the best place to look for further is
the Bonny Doon web site. Also, there will be lots of images of the
pieces that came out of this workshop on the hydraulic die forming
forum at this site. It will be fascinating to see what wonderful
things these pre-forms will become.
Anne Hollerbach