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Casting?


#1

I am new to the list, and have just been lurking out here. When
the question of vacuum casting vs centrifugal casting came up, I
just have to throw in my 2 cents and that is about what it might
be worth. I agree with almost every thing that Peter Rowe had to
say. I have been casting since the very eary 1970s, and I have
been teaching silver casting to Junior High and adults for over
25 years. I believe that centrifugal casting is the only way to
cast sterling silver. I do not cast much gold.

I have to disgree with those who recommend vacuum casting. I
have both in my shop. I use the vacuum casting machine only to
vacuum my investment to eliminate bubbles. I believe suppliers
want to sell vacuum casters because they sell for over $700.00
and there is more profit than a less than $400.00 broken arm!
The vacuum caster that will cast 1000s of casting per day also
cost thousands of dollars. Usually over $10,000.00 and most over
$20,000.00.

I will also tell what a centrifugal caster can do that a vacuum
caster can not do. I cast 10 to 20 items (everything from rings
to pendents) in one 2 1/2" x 3 1/2" flask and I cast 10 flasks
nearly every day and I get 100 percent of every cast, even if I
am casting natural objects, such as Mountain Alder “pinecones”.
I have never talked to anyone that could come close to this
volume with a $800.00 vacuum caster. I cast all ten flasks in
less than an hour and if I am in a real hurry I can do all 10 in
a half hour, by my self. And, I will agree once again with
Peter about the density and higher quaulity of the castings.

I taught junior high students to use both casters for 13 years
and adults in private classes that I teach in my own classrooms;
one in Boulder and one Loveland, Colorado. I have never had one
person get their nuckles scraped and especially never had anyone
burned with flying silver. Of course, I followed the
manufacturers suggestion and built a box around my centrifugal
casters, but common sense would have told me to do that!

Man, the more I type about this the hotter I get. There is just
so much misout there, that a new person to casting
has to pick and choose what they want to use. I have cast
100,000 castings in the past 20 years by my self. If you doubt
this I will give you references! I beleive that, for a beginner,
steam casting is better than vacuum casting. It will only cost
you about $50.00 to make a kiln and caster, buy a torch and some
investment and start casting. Your casting will be as good or
better than vacuum casting. There was a very good article in
Lapidary Journal in the past six months. I only disagreed with
that author with the elaborate equipment he thought everyone had
to use.

I have taught many kids and adults to steam cast with a flower
pot for a kiln and a jar lid packed with paper towels for the
caster. And they got the same results, but more consistant than
vacuum casting. Steam is more powerful than vacuum and gives a
more dense casting.

So, if your doing this for a hobby or small business try steam!
If you are going to do a lot of casting use centrifugal casting,
but buy a vacuum caster for debubblerizing your investment. Just
do not use it for casting. Think about it for a moment. What
actually moves the silver into the mold. It takes some kind of
force. The weight of the small amount metal and the quick rate
of freezing (cooling) prevent just pouring into the mold. You
must force it in to the mold and I believe the more force the
better the casting.

A vacuum caster only has the force of the air in the atmosphere
that is “sucked” back in to the bell jar after you have created
a vacuum in the jar. There is no magical force flowing, it is
just the amount of air that rushes back in to the bell jar! And,
that is not much. Many years ago I read an article in one of the
rockhound magazines about a man who built a vacuum machine out
of a vacuum sweeper. It makes more sense to me than a vacuum
caster, because it can move more air to “suck” the metal in to
the mold. I still think the power of steam does a better job.

The great thing about teach junior high kids is that they will
do every thing just opposite of what you tell them. I have had
10 to 20 waxes placed in one flask, and with only a 16th of an
inch of investment over the top of the highest waxes. I have
never had a back of flask break out! May be I am just lucky, but
I perfer to think it is because all the great advances in all
the supplies that I have seen in the past 25 years. Investments
these days are unbelievable.

Remember, I cast mainly silver, just a little gold, but a lot
of silver every week. Probably more than most. I am not
bragging, because it gets tiring and boring at times. I just
want you to know that I am a caster and have been for 25 years.
If you are a manufacturer of vacuum casters or sell them please
do not flame me either. I have two vacuum casters that I would
never do with out! I just do not use them for casting and still
recomend them for every caster if they can afford them. Or, I
suggest they buy a vacuum caster first, cast enough on it to
make enough money to buy a real caster, a centrifugal caster.
Or, of course you can always buy one of those $20,000.00 vacuum
casters. I have never got to use one of those. I bet they are
great!

If you wish you can visit my site of the Colorado Academy of
Silversmithing and Art Metal at http://www.frii.com/~dnorris.
We can carry on this discussion on my questbook or we can chat
using ICQ. My number is 20830163.

I am sorry if I have come on too strong, but I have been
teaching casting for too long not to have very strong opinions
about the ways I teach. I hope I have not hurt any ones
feelings!

Don Norris
@Donald_Norris
PO Box 2433 Estes Park, CO 80517
http://www.frii.com/~dnorris


#2

Don ,I can tell that your a teacher because you dot have a clue
how to do production work.I have a small co . put out 300-1000 pc
a day,gold,silver,bronze.The thought of using a spin caster would
triple my insureances rates 3x.Too dangerous. vacumme casting
only wayto go.I built my production table for less than 2 gs.
used it for 4 yrs now.get a clue. Marty


#3
  A vacuum caster only has the force of the air in the
atmosphere that is "sucked" back in to the bell jar after you
have created a vacuum in the jar. There is no magical force
flowing, it is just the amount of air that rushes back in to
the bell jar! And, that is not much. 

Just what are you talking about? The bell jar is used to
debubbleize the investment. Molten metal is poured directly into
the sprue opening of the casting ring while vacuum is applied on
a separate table set up for casting. You must be doing some other
vacuum casting I have never heard of.

 Think about it for a moment. What actually moves the silver
into the mold. It   takes some kind of force. The weight of
the small amount metal and the quick rate of freezing (cooling)
prevent just pouring into the mold. You must force it in to
the mold and I believe the more force the better the casting.>>

Yeah? Well, duh! What do you think vacuum does? It sucks the
molten metal into the mold. I think you need to get a better
understanding of what you are “teaching”. I gave up spin casting
as a primary method years ago. Vacuum is my preferred method.
Much safer and quicker for me.


#4

Well, Don Norris, It seems like you and i have very similar
experiences… except that i have taught vaccuum casting very
successfully over many years … and cast 1000’s of pieces per
week in sterling!!!LOL … Many of my items have very wide smooth
flat surfaces that require an absolute mirror finish.

I use a very cheap flat platten vacuum caster…and i use
tyvac Paper vacuum enhancers that i developed almost over 10
years ago…( only recently started marketing them). when you use
these vacuum enhancers, you will notice that the gauge on the
vac pump (when ready to cast) should only read around 26"
mercury… When the metal is poured… you will see the gauge
reach 29+ inches of mercury(if your pump is in good condition and
your seals are good). What this shows is the effect vac has on
the metal. If on your present vacuum casting system you see
almost no rise in your gauge before and after the pour… then
you are not using a vacuum enhancer … or your flask is too big
for the item/items you are casting… or your pump really isn"t
sufficient… seals could be bad, flasks could have nicks and
gouges. Inexpensive perforated flask systems are NOT as efficient
as flat platten vac casters due to the fact that on the
perforated flask system there is a chamber that needs to be
vacuumed as well and that the pumps in those systems have to work
extra hard to get the same instantaneous results (which they do
not) because both machines use the same size pump. A 1"
difference in vacuum will make a world of difference in
investing as well as casting.Most people do not realize this. When
i teach casting… i teach both systems and show that both
systems can produce equaly good castings provided that all
available knowledge on both systems are taught… also, i teach
the differences in alloys that are available on the market…
some that are incredible…of which i am sure many people have
not had the pleasure of experimenting with. I have never had an
accident with students ( due to close supervision when
instructing)…but while i was on the road selling Jewelry
supplies… years ago… probably went into well over 3000
factories from small to very big… world wide… Switzerland,
Germany, Italy, 20 years in Thailand, Hongkong, Russia,Taiwan…
The only system where i saw accidents happen was on
Centrifuges,Oh… saw one guy vacuum casting who poured metal on
his foot!!! Glad he was wearing heavy leather work boots! there
are ways doing anything… casting with cuttlefish,sand,clay… I
hope i didn’t make too many enemies out there… but i have been
through a lot seen a lot… and just the same as you … am
expressing my view points… good wishes Daniel Grandi


#5

Hi marty, I don’t know where you are coming from…I guess this
is one of the problems of Orchid…there are so many messages
that one can loose track of who said what. About 20 years ago, I
did use spin casting, until I floated about three inches over an
employees head. After that I used a chickie bar, until I bought
a vacuum machine, I have used that constantly since then.

It is true that I moderate or teach a silver group, Before I
retired I worked at a jewelry factory, did the rubber molds and
was in charge of the stamping dept. Made metal molds and was
general catch up in any department. My background is an
apprenticeship in engraving and bright cut diamond setting.

I have managed a jewelry repair shop for a 10 store jewelry
chain, and later owned that shop. Unfortunately I was a better
craftsperson that business manager.

I would always recommend vacuum, any day of the week.

Nice offense taken.

don


#6

I need to get a simple wax ring cast (just one), in 14k, and
quickly. Finishing would be nice too. The wax weight is about .5
grams before sprues, and I can sprue it myself. Please e-mail me
off-list if this is enough to get a rough estimate for costs (or if
not, what else is needed). This is for a friend of mine as a gift for
his girlfriend.

– M. Osedo
http://www.studiocute.com