I am considering casting equipment for my small, in home studio.
I inherited a small centrifugal caster that appears to have a broken
spring. Is this a repair that I can tackle on my own? However,
since it is a small unit, I am considering a larger, new set up.
In considering new equipment, any advice on centrifugal casting
versus vacuum casting? Any advice on kiln selection?
I have both air/acetylene and oxy/acetylene torches.
Any advice would be welcomed. Thanks.
Alice.
Hi Alice;
I think if I were you I’d skip over the idea of a larger centrifugal
unit and just get the vacuum machine. You’ll have much more
versatility in sprueing pieces if you can vacuum invest them, and why
not buy a machine that will serve you to vacuum invest and also
vacuum assist cast? You can get the small centrifugal machine fixed
later and buy just the bigger casting arm (about $125), not the whole
machine. My situation is exactly like yours, except my small (dental
lab) caster didn’t have a broken spring, just a bent axle, which I
was able to straighten. Now I use the vacuum primarily, but
occaissionally use the centrifuge, especially if I need to cast in a
colder flask. I never have gotten around to getting the bigger
casting arm, though. By the way, as for getting the machine fixed,
call the manufacturere and see if you can get the part and put it in
yourself or look up this guy that posted a message here in the forum;
John Cranor, The Jewelry Equipment Dr. http://www.equipmentdr.com
good luck,
David L. Huffman
Hi David,
Thanks for the answers to my vacuum vs.centrifuge question. You’ve
reinforced my feelings as to why I should choose vacuum casting.
But you’ve brought up a couple of new questions…Why does vacuum
allow greater versatility in sprueing? How does sprueing differ from
that done for centrifugal casting? Are there other differences? What
are the limitations (if any) of vacuum casting?
Thanks in advance.
Alice.- in WI where today’s rains are choking even the frogs
I’m not David but I will be happy to add my 2� worth here. Cent.
units can be dangerous if the bottom of the can comes apart or you
try to shoot too much metal. Also a bigger unit can take your arm
off if you tangled up in it. You really should have a vacuum unit
even if you are using a cent. caster so you can vacuum your
investment and invested pieces. You are limited to size of can on
Cent unit faster than on a vacuum unit. With a vacuum unit you have
the vacuum for the investment bubbles and relatively large can
capacity. Vacuum unit takes up less space and you don’t have to have
the space bolted to the building as with a cent unit. We have both
and only use the vacuum unit.
John Dach
MidLife Crisis Enterprises
Cynthia Thomas Designs
Cynthia’s sculptures are at: http://www.mlce.net
Maiden Metals,
I wasn’t clear on that, I think. It’s vacuum “investing” that
differs. Without a vacuum, you must make sure that air can’t get
trapped in a wax, as that area will fill with metal. Imagine a domed
ring, hollow underneath the dome. You would have to put the sprue on
the dome so that the air wouldn’t get trapped under it. No problem,
unless you have a pattern on that dome, or some channels cut in it
for stones. With a vacuum, you can put the sprue on the bottom of
the shank, and the vacuum will remove the air from under the dome.
As for other sprueing considerations, that depends on the piece, but
generally it’s the same. I tend to use heavier sprues with
centrifugal, since I usually cast in a colder flask. One thing about
vacuum, you can usually cast with much larger quantities of metal.
You can use very large flasks, especially if you have the type of
vacuum caster that allows you to use perforated flasks. You can also
melt your metal in an electric melting unit, which will allow you to
have somewhat better casting results, since you aren’t putting a
torch to the metal, rather, it’s being melted in a graphite crucible
with very little air present. Some people believe you get denser
castings with centrifugal, but I don’t know about that. I believe a
metal’s “density” is fixed depending on temperature. . .it doesn’t
"pack" like ice cream. But someone might correct me on that and I
couldn’t give an informed argument. I think there are others here
who have better knowledge about casting in general. I’ve been doing
it for some 25 years, but we’ve got people here who do serious
production casting and are real specialists in that area. I’m hoping
they’ll contribute here.
David L. Huffman
what about the Neycraft caster. Just how safe is it? the ads say
that it is very safe, and is contained in its own shell. Any one
have and experience with the Neycraft caster? thanks- Alma
But you've brought up a couple of new questions...Why does vacuum allow greater versatility in sprueing? How does sprueing differ from that done for centrifugal casting? Are there other differences? What are the limitations (if any) of vacuum casting?
Alice, allow me to disagree with David here. I personally find that
sprues are LESS critical with centrifuge casting. Heres the
differences as I see them:
With vacuum casting, you are not limited as to flask size. You can
do really big flasks, so long as your burnough kiln can hold them, and
your vac pump can pull a sufficient vacuum on them. Witn centrifuge
casting, your arm has a definate limit on the size of the flask.
with vacuum casting, the force on the metal driving it into the flask
is ONLY the weight of the column of metal, plus the relatively modest
14 psi atmospheric pressure bearing down on the sprue. That’s usually
only a couple psi or less, of pressure pushing the metal into the
mold, and in most cases, the plain old weight of the metal column
exceeds the atmospheric push. It’s a misconception that the vacuum
pulls the metal. It does not. It only removes the air whose pressure
and presence would otherwise oppose the flow of metal. Now, with a
larger flask, sprued as a tree, the weight of the column of metal
will be quite substantial, and exert a considrable amount of pressure.
with a smaller flask, it won’t.
By contrast, with a centrifuge, what you’re doing is to greatly
increase the effective weight of the column of metal. The force
driving the molten metal into the mold can be many, many times greater
with a centrifuge than with a vacuum casting setup. This has several
implications:
Centrifuge cast flasks fill faster, as metal is moving faster, and
they tend to fill more completely, more easily, for a given casting
temperature and sprue arrangement, with the result that substantially
lower flask temps can be used, and sprues can sometimes be somewhat
less substantial and still get a complete fill. This lower flask temp
means the metal will then solidify more quickly, giving you finer
grain size, and resulting in stronger, denser metal. So in theory, at
least with small flasks, you’ll get better castings with a centrifuge.
However, in practice, this sometimes isn’t always the case, since the
extra force on the metal, and stress on the flask, can work against
you. Investment is more prone to break down or fail when the metal is
slammed into the mold with a centrifuge, so you can get inclusions of
investment more easily, and mold breakdowns more easily with
centrifuge casting. Your investing technique must be better, and the
way you sprue the models must be a bit more careful to avoid thin
sections of investment that can easily break away. And your spruing
technique should also take into account that the metal will be moving
faster, so take care to avoid channeling the sprue into fragile
surfaces, right at sharp corners, or the like.
Personally, I’m set up to do both. With a small flask of say, one or
two rings, I’ll always cast it with the centrifuge. My results that
way are far superior and more reliable. but if I’m casing a tree with
a dozen or two rings, and pouring three or four ounces of metal, then
I’ll vacuum cast it. If I’ve got a large enough mass of metal, and a
tall enough sprue column, then I’ll get reliable good results (and
yes, virginia, it really is the height of the molten metal column
above the mold cavity that determines the pressure on the metal, NOT
the overall weight of the metal you’re pouring, not the width or mass
of the button (beyond it’s contribution to the height of the column),
or the diameter of the tree sprue. Think about that old measure of
barometric pressuRe: Inches of mercury…" Doesn’t rely on the
diameter of the column at all, just the height (and of course the
density of the metal itself), and the pressure indicated will be
accurate for any shape of column, despite changes in diameter or
directions it flows.)
Vacuum casting is easier to do, and generally safer. And there are
more places in the procedure where a mistake or inaccuracy in the
process won’t kill the casting. but when you can use a centrifuge for
a give flask or a vacuum setup, the centrifuge will generally give you
a better casting, so long as you’ve got your process controls down
right.
Peter Rowe
Alma, I have been using a Neycraft cent caster on and off for many
years and find it to be very safe and effective. I have it bolted to
my shop counter top so it won’t fly around the room. I like it. It is
simple to operate and for those who don’t have to cast everday it is
very adequate. Cheers,
Don at The Charles Belle Studio where simple elegance IS fine
jewelry!
I have used a neycraft caster for 6 years and have had great results with it.
As far as it being safe I had 2 flasks blow out the bottom and the metal stayed with
in the tub.Just make sure you keep the lever you lock down free of investment it
will not release properly when your ready cast.
Tony
Cecena’s Jewelry
Antonio Cecena
Got one and used to use it a lot. Broken can bottom or and
attempted metal overfill can and did, shoot metal around the room at
times. Hot in the hair and expensive especially if it was a high c
gold. None of this with the vacuum system.
JD
MidLife Crisis Enterprises
Cynthia Thomas Designs
Cynthia’s sculptures are at: http://www.mlce.net
Maiden Metals,
I have one and have used it for at least 12 years with very good
success. I have even cast small platinum heads with it. I have had
a few blow outs and it has always contained all the metal inside the
shell. Never has it flown across the room. I have even had my kids
cast and always had very good success. Another advantage I found is
that if I want to cast a very small flask for only one ring ( 2" X 3")
no problem. I have also cast flasks with as many as 100 rings per
flask. I love it. I have had very good results with it and have less
problems balancing the machine for different size flasks than with
other type spin casters. Yes I work for Rio Grande but we sell many
types of casting equiptment. This is just my opinion after 29 years
at a bench. Phillip Scott GG
what about the Neycraft caster. Just how safe is it?
Neycraft casting machines are quite safe, fairly compact and user
friendly. The counter weight system allows you to keep your machine
relatively balanced, without a lot of inconvenient balancing or
fussing. You pretty much classify your flasks by (1) no
counterweight, (2) counterweight in inner position and (3)
counterweight in out position. The flask holder will take standard
flasks us to 4 x 4 without having to make saddles to hold the flasks
in place. The basin is easy to sweep up for metal flashings. And
lastly, I just use C-clamps to clamp the base to a table top.
I’ve used a Neycraft for the last 6 years and like it very much. The
main drawback is that you can’t run flasks larger than 4 x 4 inches.
It’s not really meant to be a production caster, more of a small shop
casting machine.
Previously, I used a Kerr broken arm caster with a 6 x 4 inch flask
capacity. By the time I made a containment well and bolted it down
to a table top, it took a lot more space and was less user friendly.
I had to worry about balancing the flasks with the casting metal and I
had to make different sized saddles for my different flasks. It was a
nuisance to have to worry about changing saddles for the different
flask sizes.
Hope this helps you.
Donna Shimazu
Alma, when I took a casting course at Conner’s Jewelry Institute in
Georgetown, Indiana a couple of years ago, we used a Neycraft
centrifugal caster. The unit was secured in place by being mounted
on a counter top. We used it for both gold and silver and had no
problems.
The caster was wound by turning ten times and then locked. I believe
it was ten times, if I remember correctly. The gold was then placed
into the crucible and heated with a torch until it flowed. Borax was
added to the molten metal and stirred with a quartz rod. The flask
was then removed from the oven and mounted in the caster; working as
fast and safe as possible. The torch was again applied to the metal
to keep it at the flow point. The torch was then moved a safe
distance away and the caster released to spin and do it’s work.
Besides our class projects, we would also practice by make gold rings
and settings for Charles Conner for use in his stone setting classes.
These casts were on trees containing approximately six items. I
took two of his stone setting classes and had no problems with
porosity in any of the items we cast.
One time we found a small amount of gold, about 2mm in diameter, in
the metal shell where it flew out from somewhere during the casting.
Wherever it came from, the shell that surrounds the centrifuge caught
and contained the gold.
I haven’t cast since I took this class, but I do plan on buying a
Neycraft when I begin casting. I was trained on the Neycraft and
feel comfortable using it.
Charles Heick
Thanks all for your comments on the Neycraft caster. It sounds just
like what I need—user friendly and safe. Thanks again for helping
me decide.- Alma
Hi Jon
Eventually, I would like to try some vaccuum or centrifugal casting, but finances are still a little limited...
If you check with your local rock clubs, look through old versions
of the following magazines (I’m sorry I don’t remember the issues
right now): Jewelry Making Gems and Minerals (my personal favorite
for do it yourself it is now out of print but many rockhounds have
copies); Lapidary Journal (http://www.lapidaryjournal.com/); Rock
and Gem Magazine (http://www.rockngem.com/).
The last two have make it yourself equipment too, just not as often.
Lapidary Journal has an index to help access past articles. When you
are ready for production though you will probably have to purchase
commercial equipment. For newbies and small scale production these
home-made equipment works well and is usually inexpensive.
Karen Seidel-Bahr the Rocklady
May your Gems always “Sparkle”
Lapidary Journal has an index to help access past articles.
I should offer that I have a fairly extensive collection of old LJ
issues, in chronological order. If anyone is looking for a specific
old issue, drop me some email and I’ll see if I have it. BTW, LJ
Books is now selling the current index (up to 1990?) for something
like $12. No word on the availability of an updated index. Maybe
they’ll put it online…
All the best,
Dave
Dave Sebaste
Sebaste Studio and
Carolina Artisans’ Gallery
Charlotte, NC (USA)
dave@sebaste.com
http://www.CarolinaArtisans.com
Hi Jon,
Don’t forget to check with your tool suppliers as well. A lot of
suppliers carry used casting (and other) equipment at a discount.
This equipment has been demo’d at shows or used for in-house
training or has cosmetic damage. You can get the details from the
salesperson.
You’d be surprised at what a good discount these items have. Many
suppliers even offer the same warranty on used equipment as on new.
So when you’re ready to purchase, ask your supplier if they have a
used version of the item you want. They might not have one
available, but if they do, you’ll be glad you asked.
Elaine Corwin VP Tech Services Gesswein Co. Inc. USA www.gesswein.com
Eventually, I would like to try some vaccuum or centrifugal casting, but finances are still a little limited...
Perhaps my “never-throw-anything-away” philosophy will be of help
here. There is an article entitled, “$5 Casting Machine,” by George
H. Eash, in the November 1973 issue of Rock & Gem magazine, pp.
60-63. I started to make one, but lucked out and was able to buy a
centrifugal caster from someone who was retiring. Hope this helps. Judy
Bjorkman
You'd be surprised at what a good discount these items have. Many suppliers even offer the same warranty on used equipment as on new. So when you're ready to purchase, ask your supplier if they have a used version of the item you want. They might not have one available, but if they do, you'll be glad you asked.
Hi Guys and Gals, Elaine Corwin Is absolutely correct… I bought a
nice Ultrasonic 2 part unit
( seperate generator) from Gesswein 4 years ago … It was a demo
model … and it was in near perfect shape… just a small scratch on
the paint and at a greatly reduced price. I have been very pleased
with the unit , it has never given us a single problem. Checking with
your suppliers for used or demo equipment is far better than buying
from a used machinery dealer or from someone on ebay… ebay and
used machinery dealers do not usually know if the machinery really
works …nor do they give you a warranty which your jewelry supplier
gives you both.
I bought 2 ultrasonics from used machinery dealers ( very
inexpensive) they worked for about 1 month and died … no
warranty… no replacement and I lost $1000… these were larger
units than most jewelers would use.
I would be very happy to buy demo equipment from Gesswein as they
have always been a good and fair company to deal with. Usual
disclaimer… just a happy customer.
Daniel Grandi
We do casting ,finishing and a whole lot more for designers and
people in the trade
Re to Daniel,
Your suggestion is a good one . I have saved $ the same way on
appliances; fridge, dishwasher, even riding mower, however, my
business is mostly used jewelry tools (some new equip). I feel like
you have criticized ALL Used dealers when we are not all crooks.
We ask a fair price, about 50% off pre-owned equipment, which is
usually more than the major companies will give you. Our new tools
usually cost less than the major co’s as well. Primarily because we
deal in cash on equal quality equipment. My used equipment is always
tested before shipped. Should it arrive with a problem, I arrange for
repair or refund. Any unsatisfactory equipment is refurbished before
sold. On refurbished tools there is always a warranty period
according to the type of equipment. I am a veteran Jeweler of 25
years and started my business in an attempt to offer good quality
equipment at reasonable prices.
Sincerely, Jay P. Jewels Tools e-mail at,