A 'mini' burnout oven and a 'mini' casting machine are long
overdue. Just a complete mini desktop setup.... a tiny oven with
programmable temp control and a tiny casting machine at a
'realistic' price should sell very well. Just the jewelry school
student market alone would be large.
I recall having just such a setup back around '68. I was fooling
around with jewelry while in high school, while working part time at
a local lapidary shop, and my boss there found this kit for me in one
of the catalogs. marketed to hobbyists more than pros, it was a small
oven with a preset burnout temp, not programmable, but it didn’t need
to be. About 4 inches square by around 8 inches tall, top loading…
The casting part of the thing was a pressure caster, not a
centrifuge. You’d pump up the pressure with what amounted to a
bicycle tire pump, though it was aluminum, built into the handle,
with a spring loaded pad on the front, lined with what was probably
an asbestos fiber pad. You were to invest your wax model using a
supplied sprue, a wax injection that looked a bit like a mini
pitchfork, the tines of which were about 12 guage wax wire.
Invested, you’d then carve a cavity in the top of the flask, exposing
the multiple small tines, so after burnout, that became the melting
crucible, and those times formed small enough holes the melting metal
wouldn’t flow in until forced. The kit came with small torch, by
Ronson, I think, that used disposable butane cartriges. You’d melt
the metal in that cavity in the top of the burned out flask, and
press the pumped up casting “handle” down onto the flask. Between the
steam from the pad, and the air pressure released when you pushed
down, it did a fine job of casting one ring at a time. The whole
setup wasn’t much bigger than a shoe box…
Of course, you can do the same without the pumped up pressure
caster. A wet newspaper pad inside a jar lid nailed to a wood handle
works just as well, since the steam pressure is quite enough to cast
a flask invested this way. After college, I couldn’t afford a pro
casting machine, so at first a cast things the same way that little
kit had showed, It, by then, was long gone somewhere…) Burnout was
over the kitchen stove. either a gas or electric stove worked fine.
The flask goes right on the burner, and over it a clay flower pot,
lined with a layer of furnace tape and aluminum foil. Takes a couple
hours to burn out, then pressure cast with that home made handle.
Very low tech indeed, My mom still has a couple pieces of jewelry I
made back then with this method. No claims on quality at this point.
She’s my mom, and would have kept it no matter how bad the casting or
design… (grin) but memory suggests the castings were actually
reasonably good…
And you can’t beat the cost of such a steam casting setup. The whole
affair probably can be put together for a few bucks. Mostly, you’ll
need investment, wax, a decent flask a flower pot, etc… Oh, and
some sort of torch. A plain old propane plumber’s torch was what I
was using back then.
Home made setups like that can work fine. My next attempt, trying to
get more sophisticated, was to try and build a centrifugal casting
machine. I mounted a wood cross arm directly to the shaft of a
vertically mounted old washing machine motor. Fitted it with a
crucible holder and a counterweight, and bracket to hold the flask.
Melt the metal, flip a switch, and voila, I’d have a casting. Or so I
thought. The whole thing was mounted inside an old wash tub, so I
figured it was safe. Bad guess. I clearly hadn’t thought through the
engineering of such a thing. Such as the stress on the support plate
backing up the flask when spinning. I’d made it out of a sheet of
brass. Looked good. But I’d forgotten about the whole centrifugal
force thing… When I hit the switch, the thing spun up quickly, and
that brass back plate bent right back. That allowed the hot flask,
hot crucible, and molten metal, to exit the whole machine at fairly
dramatic velocity. The flask proceeded to land on, and burn it’s way
all the way through, the living room’s cheap vinyl covered couch. The
crucible left a chared mark on the hardwood floor. And wouldn’t you
know it, this first attempt was trying to cast a gold ring, so I was
picking up tiny balls of gold from all over the living room and
kitchen for a week… Fortunately, gold was still not much more than
35 bucks an ounce, though then ('74), that was still a bit of money
on a limited budget…
Ah memories…
Peter Rowe