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Centrifugal casting machine side sillage


#1

Dear orchid members

I have recently get my own simple casting setup in order to do
castings my self rather then ordering from casting companies. Its
faster, cheaper and quality is better this way.

I have choosen small spring-driven centrifugal casting machine
because its cheap, simple, doesnt require electrical power, there is
nothing much to broke and centrifugal casting seems to be better
quality then vacuum(we are talking about small casting machines). I
wanted to buy Kerr Centrifico but cant get them here in Poland. But
I have found chinesse copy of it.

So I have set up everything and already done few casting in silver
and 14k gold. Casting came out nice, everything was good. But I
would not be posting here if there wasnt be any problem, right?

Machine is bolted to heavy bench, balanced before casting each
flask.

The problem is I am having side spillage - doesnt matter if I wind
up 1, 2,2,5, 3 or 4 times. I t happens with 25 gram in crucible as
well as with 90gram.

I suspect that it could be problem with crucible (but used few
different and the same thing happens) or broken-arm part of the
machine - stop pin could be “too early” so when machine start to
turn, broken- arn unwind but hitsstop-pin and some of the molten
metal runs out through the side of crucible. But I am not sure about
it and that is why I would like to know if someone expriencet
something like this before, before I will grind some of that
stop-pin.

Broken-arm can go about 15 degree past straight. Is it enough? When
Machinestarts to turn I think I can hear that broken-arm reaches
that point. Should it?

I am attaching some pictures of machine and crucible. Or maybe
crucibles are bad - they are also not genuine Wesgo or Kerr crucible

  • couldnt find them here.

Any ideas?


#2

Marek,

I wanted to buy Kerr Centrifico but cant get them here in Poland.
But I have found chinesse copy of it.
Or maybe crucibles are bad - they are also not genuine Wesgo or
Kerr crucible - couldnt find them here.

That’s an interesting situation. I’m sure that orchid members are
keen to know about the resolution.

I suggest you contact the cheap customer service of your cheap
Chinese copy company and ask them for a cheap copy of an answer from
the cheap Chinese community and tell us about the outcome.

Sandor Cser


#3

Try digging out some of the investment from the flask base before
burnout.

Most of the rubber flask bases you can buy have too low of a dome.
Or use a flask base you fill with clay and make a higher dome, so you
will have a deeper depression in the flask.


#4

Hi Mare,

Your crucible’s a little lower than the ones I use, but it should
work for small loads. (30gm and under) Normally, I always use the
big 200gm crucibles (the biggest ones).

The reason for the big ones is that I can use the crucible to trap
fuel gas from the torch over the melt, to shield it from oxygen.
(Mix the torch a little reducing, and it’ll do this automatically.)
So the big ones give you better castings, and you don’t have to keep
several sizes around. Just get the big ones and you’re done.

You are remembering to set the broken arm all the way over to the
’broken’ side, right? The whole point of the broken arm is to keep
metal from spilling out the side when the thing first starts. If the
arm hits the pin once it starts to spin, you will hear the most
amazing noises, as the machine tears itself apart. Side spilling
would be the least of your problems in that case. I always pull the
arm back, wait for the pin to drop, so I’m sure it’s down, then
let go. So there’s no way it can hit the pin.

The reason the broken arm can go past “straight” is to keep it from
bumping the end when it swings out. When it swings because of the
spring, it swings out straight very fast, and then the centrifugal
force stops it when it gets to ‘straight’. (It goes a little bit
past, then comes back, which is why the arm goes to 15d past
straight.) 15D Should be plenty. The metal is almost all inside the
flask by the time the arm snaps out straight. It all goes in to the
mold in the first 1/4 revolution or so. Everything after that is
just holding it in place while it cools down.

My first answer would be to use taller (bigger) crucibles, and see
if that doesn’t solve the problem.

Hope this helped.
Brian


#5

If you look at the side of your crucible you can see the spill mark.

Change crucible to a deeper one.

Gesswein # 260-8900

Or

Rio Grande #704-045

If you spill from the front between the flask and the crucible you
need to grind the crucible so it is closer to the flask.

The spru base could also be a shape that may spill. A round shape
spru base (where you attach the spru wires) spills less. Or the flat
top ones also.

Be careful not to have too much metal in each cast. Excess metal
will also spill.

Regards,
Todd Hawkinson


#6

You need to start the cast with the arm already in its broken
position, against the stop. It will straighten out when spinning.

Elliot Nesterman


#7

First thing that comes to mind is that the machine should be set
with the flask holder pressed against the stop so that the two parts
of the arm are set at 90 degrees. Any other setting will cause the
arm to flop about and spill metal.

Have you done that?
fred