Homemade Centrifugal Casting Machine
Gabe Wizard
centrifugal casting machine, using a heavy gauge spring to provide the
spin for the mold. Does anyone have any info on such a device? It seemed
to be a fairly simple construction project, but I wouldn't want to do it
incorrectly. Nothing like having molten silver or gold flung in a wide
circle to get your attention!
Brett Gober
: Nothing like having molten silver or gold flung in a wide
Which is why you should not even think about making one yourself. A
simple centrifugal caster is cheap and lasts for years and has the added
benefit of being safe to use.
Peter W. Rowe
>A long time ago I came across a book that showed plans for making a
>centrifugal casting machine, using a heavy gauge spring to provide the
>spin for the mold. Does anyone have any info on such a device? It seemed
>to be a fairly simple construction project, but I wouldn't want to do it
>incorrectly. Nothing like having molten silver or gold flung in a wide
>circle to get your attention!
Don't know about your article, but my first casting machine was a
homebuilt. I used a vertically mounted 1/4 hp washing machine motor,
with an improvised wooden (walnut no less, as it's what I had handy)
broken arm mounted directly to the shaft. Some scrap brass formed the
counterweight, and the curcible holder and flask cradles were also
brass. To cast, I just hit the switch. Sheer ignorance and blind
faith substituted for an enclosing tub around this whole affair, which
was located, for want of a better place, in the center of my one
bedroom apartment's living room. Flasks were burned out over the
kitchen stove's gas burner, covered with a clay flower pot, which I'd
lined with asbestos furnace tape (It was still available in '75, and
who knew better...) and aluminum foil.
In dry runs, the machine looked like it would work just fine. In it's
first actual run, though I discovered that the 18 guage brass sheet
which served to back up the flask, wasn't at all heavy enough to hold
that flask and crucible in place when spinning. Not surprising, when
I melted my metal and hit that switch, the machine spun, the plate
instantly folded back under the centrifugal force, sending the hot
flast over to burn a hole in the couch, the crucible to land on the
rug, and most of my ounce of gold in tiny bits all through that rug.
Amazingly, I wasn't hurt. After I realized what I'd done, and
replaced that silly piece of brass with some heavy steel angle iron,
the machine performed as intended. With it's new splash shield.
Even more amazingly, I even managed to pick out most of those bits of
gold from the rug, and the flask, having gently cooled in the nice
soft hole it'd burned in the couch, was none the worse for wear. Two
days later, with the machine revamped and the same flask reheated, I
tried it again.
My mother still has the ring that resulted....
Needless to say, when I left that apartment, I didn't get quite all my
security deposit back...
Fond memories.
Peter Rowe
Gabe Wizard
: Gabe Wizard (gwi...@crash.cts.com) wrote:
: : Nothing like having molten silver or gold flung in a wide
: Which is why you should not even think about making one yourself. A
: simple centrifugal caster is cheap and lasts for years and has the added
: benefit of being safe to use.
Oh come on, I can _think_ about it. I may come up with a safe way to do
it, if I think about it long enough. And I'd have to disagree. Even a
"simple" centrifugal casting machine is expensive. It all depends on
what you consider expensive, of course. If I can build one, a safe one
that is, from $40 worth of parts, I'm likely to save myself a couple
hundred dollars, or more, which I could then spend on metal....
Seems to me that a big part of making it safe would be some type of
shielding. Ideas?
Gabe
Peter W. Rowe
>Gabe
Shielding is the easy part. Go to a decent farm supply or hardware
store and get a large galvanized washtub. You can get these large
enough to mount, for example, a kerr centrifuge in, and if you design
your machine along the same size lines, you can do the same for your
spash shield. Or you can make a tub of some sort from plain
galvanized sheet metal too. Your choice.
Harder, in building a cetrifuge is the question of powering it. A
spring driven machine might be difficult to engineer solidly, and get
acceleration rates correct. A lot easier would be to copy the motor
driven centrifuge designs, where all you need to do, after choosing a
suitably solid and sturdy arbor for the casting arm itself, is useing
the correct drive pully ratios to provide a reasonable rpm. The
commercially made versions use a variable drive, so you can choose
your rpm. The commercial version I've seen also incorporates a "dead
man" type switch, where the motor only powers up when an overall lid
is closed. Opening the lid cuts power to the motor. A good train of
thought, safety wise, for your design.
And you also need to design an arm that will have provisions for being
correctly balanced, hold the flask securely, hold the crucible
securely yet allow it to be moved up to the flask easily in the
casting process, even when hot. And the whole affair must also be
strong enough to withstand the centrifugal forces you're going to
impose. At a reasonable rpm, that little flask on one end, and the
counterweight on the other end of the arm, weighing only ounces or so
at rest, can impose loads of many hundreds of pounds on the arm.
While it's easy enough to design a splash shield capable of protecting
you from molten metal splashes and similar mishaps, It's not likely
that you'll have a shield that can deal with a high rpm casting arm
breaking in half at the pivot point and having both halves fly off in
different directions or the like...
Hope this helps.
Peter Rowe
darylb
wrote:
>
> Oh come on, I can _think_ about it. I may come up with a safe way to do
> it, if I think about it long enough. And I'd have to disagree. Even a
> "simple" centrifugal casting machine is expensive. It all depends on
> what you consider expensive, of course. If I can build one, a safe one
> that is, from $40 worth of parts, I'm likely to save myself a couple
> hundred dollars, or more, which I could then spend on metal....
>
my garage). If you find plans then I would be interested. Particularly the
drive spring part which I can't see when I look at these things. They want
$540 for a tiny one here.
lionel pepper
>A long time ago I came across a book that showed plans for making a
>centrifugal casting machine, using a heavy gauge spring to provide the
>spin for the mold. Does anyone have any info on such a device? It seemed
>to be a fairly simple construction project, but I wouldn't want to do it
>incorrectly. Nothing like having molten silver or gold flung in a wide
>circle to get your attention!
Some years ago I had the same problem. I needed a centrifugal casting
machine but couldn't afford to buy one. However, I had a workshop
with engineering facilities to build one. Some years earlier, I had
seen a very Heath Robinson machine built from an old bicycle, but I
thought that a spring driven one would be much better and fairly
straightforward - it WAS NOT.
The first question was whether to make it a horizontally or vertically
mounted centrifuge. Vertically mounted machines have the advantage
that the centrifuge arm can be straight and by releasing the arm
upwards from a horizontal position, the melt is less likely to splash
from the side of the crucible; they have the disadvantage that they
are LETHAL ! Despite a guard, any splatter of molten metal is likely
to escape.
A horizontal machine, however, needs a 'broken-arm', otherwise the
fierce initial acceleration causes the melt to flow out of the side of
the crucible. Such a broken-arm adds some complication to the
design.the big problem with any spring driven machine is that the
initial acceleration on release IS fierce andvery hard to control.
One of the difficulties in a small casting machine is that of
counterbalancing the weight of the flask, the melt and the crucible.
Where a number of flasks of different sizes are being taken red-hot
from the kiln, it is just not practicable to adjust the
counterbalancing with each melt.. In a large, heavy machine this is
less of a problem but a small, top-heavy spring driven machine is
rather inclined to try to tear itself from its mountings. Besides,
such a high initial acceleration is not necessary.
Another danger of a spring drive is the risk of premature or untimely
release of the trigger. The risk is lower with a motor driven machine
- but consider:
A motor with sufficient power to quickly start a centrifuge arm with
its high inertia is quite an expensive piece of kit and requires a
mounting and drive pulleys, belts, etc. It has to reach maximum speed
within say 5 seconds at most ( and that's too slow) ; it may then be
turned off, as it is pointless to continue driven rotation after the
melt has solidified. Say you are casting twelve flasks in a session
and you are casting once a week ( that represents a lot of individual
castings if you are finishing them yourself). Get the point......?
Is it worth using a motor for one minute per week ?
That was the problem I had around 13 years ago when I built my
second casting machine after the clockspring driven prototype
proved .........unsuitable! A strong fixed horizontal arm, big enough
to take 4 x 6 inch flasks (at a pinch) was what I wanted (though I
rarely use anything so big preferring 3 x 4 inch for most work).
So what about HAND power. I took another idea from the clockmaker and
built a hand-powered centrifuge using a FUSEE pulley. It's a tapered
pulley with a rounded groove designed to hold a length of nylon cord -
about 6 feet. The cord is wound up under the machine, ending on the
widest part of the fusee. When the metal (heated by a blowtorch
clamped above the machine) is molten and the hot flask in place in the
appropriate annulus of the backplate, I just pull the cord.
The initial torque is high, reducing as the arm speeds up. It is at
full speed within two seconds and the throw and acceleration are quite
sufficient for even very delicate castings. The total rotation time
is around 30 seconds. The machine is so safe inside its guard ring
that no splatter ever escapes. I cast around 100 to 150 flasks per
year and have been using my 'Fusifuge' for 13 years now. It needs
little maintenance.
The casting arm is fixed to a 3/4 inch shaft of EN8 steel (through
which I can apply vacuum or supply inert gas if necessary) which
passes through a block with ballraces, fastened to the underside of
the low bench (27 inches). The fusee is fixed to the end of the
shaft. The counterweight (rarely adjusted) fits on a length of
studding. The fusee took some turning up in aluminium - tricky but
very satisfying.
I hope this information is of use to you. I am sending you the plans
of the machine as a GIF (11kB) by e-mail. Good luck.
lionel pepper - ring...@tcp.co.uk
John Angus
: gwi...@crash.cts.com (Gabe Wizard) wrote:
: >A long time ago I came across a book that showed plans for making a
[stuff deleted]
: replaced that silly piece of brass with some heavy steel angle iron,
: the machine performed as intended. With it's new splash shield.
: Even more amazingly, I even managed to pick out most of those bits of
: gold from the rug, and the flask, having gently cooled in the nice
: soft hole it'd burned in the couch, was none the worse for wear. Two
: days later, with the machine revamped and the same flask reheated, I
: tried it again.
: My mother still has the ring that resulted....
: Needless to say, when I left that apartment, I didn't get quite all my
: security deposit back...
: Fond memories.
: Peter Rowe
:
Hey! The guys over in rec.crafts.metalworking have been running a long
and funny thread on "Stupid Human Tricks"
This should fit right in ;-)
John
Mark Johnson
My first attempt at c-casting was a hand sling right out of the
"Complete Metalsmith". It was amazing what goes through ones mind as
one gets ready to swing molten metal over their head. Its even more
amazing when the rope gives way and that molten metal goes flying all
over the yard. We had small fires everywhere.
Mark
Lyle Craver
jan...@nimitz.mcs.kent.edu (John Angus) wrote:
> Hey! The guys over in rec.crafts.metalworking have been running a long
> and funny thread on "Stupid Human Tricks"
You're really perverse John - a LARGE portion of that thread relates to
accidents causing permanent injury and death. (Sometimes multiple)
On the other hand I would DEFINITELY recommend it as a constant reminder
that in ANY smithing job you do safety has got to come first.
Ray Elsey
there.... I had to post an amusing jewelry related story there and figured
that it might also be amusing to post it here...
So, just for fun...
{Grin}....
I own a jewelry manufacturing and service facility, employing as many as 21
workers building, restoring and servicing jewelry... This reading of this
thread makes me remember a most amusing story, wwhich I'll try to relate best I
can... ...but the truth is, "ya had to be there for the full effect".....
I'm laughing so hard I can hardly type even though this story is over ten years
old... It made a lasting impression on my sense of humor... Read on :)
I had a gentleman working for me named Steve Yoakum, who was a bench jeweler
and
part of my workshop crew. One day he had a job to manufacture a white gold
plate, which would be soldered to a piece of silver tubing and installed into a
nice gents ring, after a diamond was set into the plate... We had pre-cut the
design and fitted the stone so all the pattern was there and the stone/diamond
needed to be set to complete this beauty... Nice millgrained edges and
beads/prongs standing tall and well defined... Nice work! By pre-cutting the
plate one can really get the definition and crispness fine jewelry is suppose
to be all about...
It is a given that at the bench one must make gravity their friend, or it will
become their enemy quickly... Well, Steve was struggeling to balence that
white gold square plate on the piece of silver tubing and trying desprately to
solder it firmly in place, and everytime he'd heat it up the plate would shift,
making the thing off center and making him start over again to realign the
parts... I happened to walk by as he was workin and muttering and cursing that
this just wasn't.... He stopped talking and there was an odd silence... He
was very quite, interupting his sentance/muttering so I started to glance back
at him...
He was looking around, sort of bewildered, oddly, with big round eyes and that
"deer in the headlights look".....
He didn't sit there looking bewildered long though, soon he quickly shot out of
his chair and started working at pulling his pants off, laughing really hard...
Now, at first I didn't get it at first, because he was laughing and disrobing
at the same time, but since this was rather odd behavior (since I employ around
half a dozen gals in my shop) I tried to understand what I was seeing....
When I saw that he'd completely disrobed from the waist down, laughing so hard
he couldn't talk... Running around in small circles holding his appendage... I
discovered quickly that the 6mm square heavy white gold plate had "slid off"
the tubing, and into this guy's lap, quickly burning right thru the heavy shop
apron, his jeans, his undergarments and welded it's self firmly to the head of
his... {Grin}... Hence the floor-show and stripper routine...
It was the most amazing thing to see this guy dancing and laughing so hard he
couldn't speak, holdin' his johnson and turning in small circles...
I must admit that my eyes filled with tears, I laughted so hard I thought I'd
die even while I was trying to help, but I sure wasn't gonna be the one to grab
that sucker and yank it off that thang... ...besides, he was zooming around
the shop like a streaker in the seventies on a college campus......
After he'd literally pried the metal off his appendage, and things settled
down, I discovered that not only had that plate burned him, but it had also
left the most interesting impression of a pre-cut plate, all nicely shaped,
with the detail fairly well defined within that "brand"... To this day Steve
has a reminder of why we make gravity our friend, and don't count on things
just not shifting when soldering parts together...
Besides, he has a most intersting topic now to discuss, how he got that unique
body decoration....... From that time on I think he discovered that the plate,
face down on a charcol block, with the tubing held in locking tweezers aligned
makes soldering part like this easy, and ya know... I still can't look at the
guy today without remembering his exotic strip routing and his maniacal
laughter and swinging appendage in his hand at the shop...
Now Steve always has something to show a prospective employer how good and
how clean his jewelry work is.... {Grin}....
Something which he can never loose...... {Grin}.... Unless he gets tangled up
with Lorainna Bobbet that is.... {Grin}....
I know it made quite an impression on both of us.......... {Grin}.....
Might even say it made a "lasting impression" on me too... {Grinning widely}
Interesting thread over there in rec.crafts.metalworking.... {Grin}....
Ray
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