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Vacuum vs Centrifugal


#1

I know its an old thread, but I am curious as to the success
rate of Vac versus Cent…

I have, and continue to try centrifugal… I believe I have tried
everything known to man and even smart apes( if they have an idea
as to how to improve my casting success.)

‘IN THE HOLE’ casting isn’t a problem !!! But sometimes I don’t
want to do but one/two etc., rings at a time… THEREFORE, I try
to do 'ON TOP . . THROUGH THE LITTLE 3/8 INCH HOLE(PLUS OR MINUS)
with a small cylinder… AND IT JUST DOESN’T WORK BUT about 50 %
of the time!!!

I pour at 900 degrees, with a vacuum, quickly, and sometimes it
just provides small or large pieces of the item . . .( Boy, have
I learned to weld!!! next note … found a good product).

So you Centrifugal out there… and other vac’er… what
percentage do u return… I have just bout had it … on to
Centrifugal??? … lost 3 or 4 nice slides which were a heck
of a lot of work!

Jim


#2

<< So you Centrifugal out there… and other vac’er… what
percentage do u return. >>

Jim, I have to say I get 99%+ positive results spinning, and I
cast 2-3 flasks a day. I have both set ups but prefer to use the
centrifuge. I am sure to be in the minority on this. I only cast
gold, and always sprue everything to the button directly. Flask
temps are 1000 deg for yellow gold and 1300 deg for white gold,
these are the recommenations of the manf the alloy I use. If you
are having trouble go back to basics, follow to the letter the
reccomendations of you investment manf and you metal supplier.
Also remember to click your heels together 3 times and bow to the
east before each melt. Mark P.


#3

Mark,

Spinning??? I’m not sure of the meaning?? . . Is spinning the
term for casting on top of the unit??

But … per manufacuer …the silicon pad which sits over the
alumin. “hole” cover recommends casting at 900 … pad scars very
badly otherwise(tried casting at 1000). No problem casting “In
the hole or container” …Just on top…

Do you must use a carbon pad???

Envey our success… I’ll try bowing to the East, West, North,
South, in all combinations if it will work!!! (WOW that’s 24
combination!!.. maybe not!!)

Jim


#4
  Spinning??? I'm not sure of the meaning?? . . Is spinning
the term for casting on top of the unit?? 

I mean using a centifuge rather than a vacume caster. Both work
well, I prefer the “spinning”. I think my success is mainly from
spueing directly to the button rather than using a tree. If we
have a 100 dwt. pour then we will vacume cast and use a tree
(this might have a couple of misses). So I almost never do that.
I prefer to have more flasks with fewer peices in each, mainly
because we carve 95% of what we cast and I don’t want to redo
any. There are certain rules you must follow regarding
investment and its handling, temperature of flasks and metal etc.
If you are unsure call the manf., like R&R or United metals or
Hoover etc. If you are having trouble you are doing something
basic wrong. Or you have angered the Gods with some unspeakable
act, too horrible to mention on this list. If that is the case I
am afaid there may be no hope for you, I’m sorry. Mark P.


#5

Mark:

i used to have a lot of trubble with my jewelry work and hair
was growing on my palms, too, so i figgured it was the
unspeakable acts and since i quit them everything has gone
better. recommend you try it if you were raised catlick.


#6

Now I understand,

I only have a Centi so I either cast on top or in the vacuum
hole… ON top I try to do only a few pieces and also don’t use a
tree…

In the Vacuum hole I do a tree and it never, Well almost never
fails… in top, for one or two pieces I usually get only a 50 %
completion.


#7
I pour at 900 degrees, with a vacuum, quickly, and sometimes it
just provides small or large pieces of the item . . .( Boy, have
I learned to weld!!! next note .. found a good product).

Jim:

I use a vacuum system and pour into flasks that are from 900 to
1200 degrees F. depending on the thickness of the wax patterns
and the metal being cast. I always use a perforated flask as this
insures that I will have optimal results. I definitely prefer
vacuum casting over centrifugal. If casting from a pad on top
doesn’t work and casting with a perforated flask does, then I
think you have answered your own question. Obviously you are not
getting sufficient vacuum when you cast on a pad.

Kenneth Gastineau
@Kenneth_Gastineau1
http://www.ud.net/gastineau


#8

Kenneth,

The vacuum comes up per usual(30 inches)… Do u ever cast ‘on
top’ … Not using the perforated flask inside the canister or
hole??

I usually have great success in with perforated flask but
sometimes I would prefer to just cast one or two small pieces and
the perforated flask are really quite big … I also have to use
my large oven instead of a small 4 inch up/down in 1.5
hours…

I don’t pour, in either cast until I have a vacuum.

Do u ever pour on top and your results if u don’t mind.

Thanks,

Jim


#9

Kenneth:

What about the idea that the silicon ring on your perforated
casting machine is only good up to 900F, which I saw mentioned by
someone here. I guess you don’t findthis to be true? Also, I am
about to start vacuum casting on a perf flask machine I bought
used, but I can only get 27+ inches of vacuum. Boils water if the
water is about 75F, but not quite at 68F. Do I mix my investment
at 75F? And will 27 inches be enough of a vacuum when casting a
4"x6" flask? Thanks.


#10

Jess,

I havens’t tried the silicon (specifiacation 900 F) in the
container with P flask… only on top… In the container I
use a carbon(think) ring but it is very, very, easy to break.

I have burned up 2 silicon pads so I now prefer to pour at less
than 900F… That is, scorched them with rings per the flask
bottoms and then u WILLNOT pull a vacuum for sure.

Can’t believe that 27 isn’t good enought I have poured with
much less and with success…

Jim


#11
What about the idea that the silicon ring on your perforated
casting machine is only good up to 900F, which I saw mentioned by
someone here.  I guess you don't findthis to be true?  Also, I am
about to start vacuum casting on a perf flask machine I bought
used, but I can only get 27+ inches of vacuum. Boils water if the
water is about 75F, but not quite at 68F.  Do I mix my investment
at 75F?  And will 27 inches be enough of a vacuum when casting a
4"x6" flask?  Thanks. 

I use a high temperature gasket that works well at 1200 degrees
F. I have been using the same one for over 5 years.

I use 100 to 110 degree F water to mix with my investment. (Hot
water method insures boiling and mixing)

I don’t know how many inches of vacuum it takes to do vacuum
casting, but I would say that if you are able to boil water at 75
degrees F, it would be sufficient. With vacuum casting I am just
as concerned about the pumps cfm’s or volume of vacuum per
minute. The one I use pulls 15 cfm, this is probably overkill but
who wants to wait.

Kenneth Gastineau
@Kenneth_Gastineau1
http://www.ud.net/gastineau


#12

Jim:

Regarding the carbon ring, where does it come from — the only
thing I have seen is the red silicon rings in the Rio, Swest,
etc. catalogs.


#13

Kenneth:

My vacuum pump is made from an old car A/C compressor run
"backwards". I don’t know the cfm it pulls, but I can boil the
water in under a minute and hit max vacuum in about that length
of time. Does that sound OK to you?


#14

I said a carbon ring… well, it is more of a black fiber ring,
ealily broken and very fradgile. Picked it up at a local
supplier. Can cast at higher temps with the ring.

But still have to use the silicon ring when casting on top …
which is where I’m having mucho problems with success.

Jim


#15
My vacuum pump is made from an old car A/C compressor run
"backwards".  I don't know the cfm it pulls, but I can boil the
water in under a minute and hit max vacuum in about that length
of time.  Does that sound OK to you?

Sounds like it ought to work to me.

Kenneth Gastineau
@Kenneth_Gastineau1
http://www.ud.net/gastineau


#16

I use a vacuum system and pour into flasks that are from 900 to
1200 degrees F. depending on the thickness of the wax patterns
and the metal being cast. I always use a perforated flask as this
insures that I will have optimal results. I definitely prefer
vacuum casting over centrifugal. If casting from a pad on top
doesn’t work and casting with a perforated flask does, then I
think you have answered your own question. Obviously you are not
getting sufficient vacuum when you cast on a pad.

When using non perf flasks, do you add some sort of aid spacer
to the flask to assist in getting the air out. I use heated,
pinched closed with pliers, plastic straws down the side of the
flask where ever the piece being cast is close. Hold the straw
pieces in place with paper clips for placements and investing.
When the investment hardens, take off the paperclips and when
ready to heat the flasks, the straw burns out (sorry about the
bit of plastic, but …) and this has worked very well for
us over the years. Perf flasks are great, but all of ours are
pretty big and a waste of material and all if not really needed.

Just another way to skin the same old cat!!!

John and Cynthia/MidLife Crisis Enterprises
Maiden Metals/C. T. Designs/ Bloomin’ Wax Works. etc.

PO Bx 44, Philo
CA 95466
Ph 707-895-2635 FAX 707-895-9332

There is no limit to what you can achieve,
if you don’t mind who gets the credit.


#17

Good idea… I have been using coat hanger pieces around the
flask… like the straw idea better… provides more area to
development the vacuum… will try the straws.

I vacuum ‘on top’ when I want to do only 1, 2 etc pieces … not
a whole cylinder … just don’t have any luck on top… was
wondering what sucess others had casting on top of the unit…

Jim


#18

I use common 6 penny nails and hang them around the edge of the
flask by the heads till the investment hardens then pull them
out. Gives nice straight round holes for exhaust. Frank


#19

The other side of the coin! from John at J.A.Henkel Co., Inc.
Casting quality has less to do with Vacuum vs Centrifugal than
it does with spruing!! What is the metal doing when it melts and
enters a confined space? Ponder that. Also, Centrifugal delivers
denser castings. This may not always be a concern. I use both on
a regular basis. Some say it’s like the difference between Mac &
IBM! As a professional I prefer Centrifugal (if someone put a
gun to my head and made me choose) If you have questions or
coments you can e-mail me… @jahenkel


#20

I vacuum ‘on top’ when I want to do only 1, 2 etc pieces … not
a whole cylinder … just don’t have any luck on top… was
wondering what sucess others had casting on top of the unit…

I used fie wax wires to ventilate the walls of the flask when
casting on top. Works fine for me. I usually use 2" flasks as
these can be burned out in an hour and it seems that everything
I do ends up being a wait job. This flask size still allows me
to do 4-6 rings at a time.

Bruce D. Holmgrain
e-mail: @Bruce_Holmgrain
http:\www.knight-hub.com\manmtndense\bhh3.htm
snail mail: pob 7972, McLean, VA 22106-7972
phone:: 703-593-4652