Jim,
This can easily be remedied by using indirect spruing and an
investment that doesn’t fall apart so easily. In 30 years the
only rings that split were those that I dropped transferring
them from the burnout oven to the cradle in my casting machine.
Regards,
Skip
Skip Meister
@Skip_Meister
N.R.A. Endowment &
Certified Instructor
in all disciplines
Certified Illinois D.N.R.
Hunter Ed, Instructor
Dan: thought I’d throw in a tip here for anyone wanting a kiln
controller. Any kiln controller you buy from a jewelry catalog is
a plain rip-off. I got a Paragon kiln controller from a ceramics
supply house and saved about $150 for virtually the same thing
some of the jewelry catalogs sell. I think anyone casting without
a controller is just wasting alot of time with inconsistent
heating; you have no idea what the heck you’re doing to your
flask without it. And Dan is right, I have a cheapo Satellite
kiln and the digital readout on the controller showed the gauge
on the satellite to be substantially incorrect even though I did
my darndest to make sure it read right. The controller is one of
the best items I ever purchased…Dave
Crystalguy Jewelry, the first art jewelry site on the net
http://www.opendoor.com/stephensdesign/crystalguy.html
Art jewelry with a mystic touch / Now accepting credit cards
Hi Bob, I believe setting up for vacuum casting would be the
least expensive… If you buy a vacuum investing/flat platten
casting machine(about $700.)This will do the plaster investing as
well as the casting. A neycraft oven witha digital control…or
similar oven…kerr makes a small wax pot with a built in pump,
gauges and regulator( so you don’t need a compressor)an Oxy
propane torch from a welding shop for melting .There are numerous
little things that i could list for you… but i would suggest
that you send out/call all the distributors and ask for price
quotes on a complete system using these machines or a similar
system… some distributors to check with are : Gesswein co tel.
800-243-4466 The contenti co. 800-343-3364 Rio Grand progess
machine tool co. Swest Most suppliers can give you a
quotation.there are cheaper ways to go , but are probably more
probleamatic…I do know that Gesswein has agood tech service
dept that can help answer many technical questions you might
have.( no… I don’t work for them) let me know how you make out.
Daniel Grandi http://www.racecarjewelry.com
Hi Skip… I have cast as many as 15,000 pieces /week on vac with
less than a 3 % loss factor. Also… did 14 years of centrifugal
casting… and tracked the loss factors at around 8%. The crown
in my mouth was carved /cast in gold by me … on a vac
system… and according to the dentist who put it in…it’s
perfect. Centrifuge Is an old art form of casting that as can be
seen by the equipment currently being made in the Jewelry field
is no longer as popular as it was in the 60’s and 70’s. There is a
reason for that… cost and quality… and danger factors… It
would be a different story if i had been a centrifuge caster
who had nothing but problems and converted to vac…THIS IS NOT
THE CASE. I had good success. I don’t profess to tell anybody who
has a centrifuge to go and buy a vac-system .I am mereely
stating that it is easier to learn and get good quality castings
out of a vac system and cheaper. Having had the experience of
being on the road selling both types of casting equipment over a
number of years… i can tell you that the horror stories
related to centrifugal castings far exceed those related to vac
casting…and these mistakes can happen to a person with years
of experience! In my experience… when someone is having a
problem in vac casting… it is usually related to something very
simple that was omited… I had one guy tell me that his castings
only came out at an oven temp of 1200oF he always had porosity
with vac… It turned out that he wasn’t using the red silicone
rubber seal / pad on top of the machine… so the flask was not
getting proper vac to begin with. how about the person who had a
gouge on the sealing part of the flask … again… lack of vac
due to inatentiveness… But one thing is certain…when you
pour the metal in a vac system … it goes down… An imbalanced
centrifuge can throw metal everywhere… I’Ve seen a retaining
bolt break off and the machine went crazy inside the protective
tub … the customer ended up loosing gold all over his shop…
burnt one of his employees … Many accidents are caused by
inatentiveness to detail… But in a vac casting system, you
literaly have to pour the metal on your foot to get Hurt!!! All
i’m trying to do in this forum is offer advice on vac casting to
those who want it …and if someone wants to ask me questions on
Centrifugal casting…i have 14 years experience doing that
also… and doing it well !
Sincerely,
Daniel Grandi
So I'll increase my temperature a bit on my next vacuum cast and see what happens. And Peter what is your opinion on the comment about different casting grain for vacuum or centrifuge ?
I’m sure Dan can correct this if I’m wrong, as he’s more
experienced in this than I am. but the basics of flask
temperature are simple. You want to cast at the lowest temp that
gives you a good and complete fill, without a bunch of porosity
just under the surface. That subsurface porosity, by the way,
is from when metal just hitting the mold wall freezes first and
well, but metal under that initial skin suffers shrinkage
porosity as it pulls away from that skin. Two things help this.
Casting with a hotter overall flask temp reduces that initial
quick freeze at the surface, and increasing the sprue size
increases metal availability so shrinkage porosity is reduced.
Another good trick is to create a temperature gradient from the
center of the flask to the outside, if you’re casting with a
tree. You do that by pulling the flask from the kiln at a
somewhat hotter temp than you’ll be actually casting at, and
letting the flask sit for a minute to five minutes, sprue hole
down. The center of the flask will cool very little, since
investment is a very good insulator. The outser areas of the
flask will cool more. so when you then pour the flask, the
sprue area in the center core, and those heavy sections of the
castings in the center of the flask, will stay fluid a little
longer than those areas of the castings closer to the outside of
the flask. This basically is to increase the degree to which the
whole tree solidifies in a progressive manner from the outside
and the end of the tree towards the inside of the tree and up
towards the button. This in turn minimizes shrinkage porosity
and metal starvation problems. This stuff all applies equally to
vacuum and centrifugal casting.
In general, though, because vacuum casting tends to fill a flask
a little more slowly, and with less force on the metal, you need
to have the flask be a bit hotter when you cast if you’re to get
complete fills. But this will depends some on the types of
things you cast, the alloys you’re casting with, and other such
variables. In some cases, you may not need to use all that much
hotter temps. In other cases, you’ll have to be 200 to 300
degrees hotter. Your results will tell you what you need to be
doing.
As to using alloys specifically designed for vacuum casting? Up
to you. These are alloys that WILL perform better in this
application than some other alloys that are not optimized for
these conditions. Whether the difference is significant enough
for you to use them depends again on your volume of casting, and
whether your current pieces are having any problems that suggest
you need improvements. Talk to your metals supplier about both
the problems you’re having and the alloys they offer. They
should be able to advise you on what aspects of their alloys will
help you, and you should then be able to make an informed
decision.
Hope this helps.
Peter Rowe
It is Don, again. Not Dan! A vacuum caster is about $700.00 to
$800.00 depending if you can find a “buy”. I just bought one from
Naja is Denver for $700.00 just last week. I also bought a long
arm centrifugal caster for $410.00 complete, also from Naja,
except for a box to go around it. I simply build a plywood box
around it then line it with stee, sheet from the hardware store,
takes about 1/2 an hour to build and your set. By the way I also
bought a Satelite kiln from them. It has an inside opening of 12
x 12 x 8 so that I can get up to 20 flasks of the 2 1/2" to 3
1/2" tall flasks. With 10 to 20 items in a flask I can burn out,
cast all 20 flasks by noon (centrifugally of course), and have
the castings ready to sell by 5:00. By the way if any one wants to
know how I sprue up 10 to 20 castings in one small flask, visit
my website, go to the questbook and request that I take some
photos and I will put them on by site. I will take my web master
about a week, but I will do it for you. I think you will be
surprised at my method and I never have a porosity problem, even
with gold.
Bob, how many casting do you want to cast a week, month or year?
It really makes the most difference in choosing one over the
other. If your going to do less than 10 a week, I really think
you should try steam casting. Really, it works. The cost is less
than $2.00 (and it will give you as good as results as vacuum
caster for casting). You still need a kiln (but a flower pot over
a camp stove will work to get started). I promise I will help you
learn how to do it, either as weekly posting here, or on my web
site. I have taught people to start their jewelry casting
business in ONE day class with steam, and only about $50.00 in
materials for the caster, kiln, and torch! They went home that
night and started casting (commercial waxes and waxes made from
my molds) rings and pendents that polished with dremel tools and
sold the next week. This gave them enough money to start buying
better equipment.
I hope this helps you make a decission. I still recomend getting
the vacuum caster for vacuuming the investment. But try steam for
10 or less casting per week.
Don Norris
@Donald_Norris
PO Box 2433 Estes Park, CO 80517
Peter,
Great … and i will certainly try these
suggestions… however, in vacuum casting there is an upper limit
of 900 degrees due to the silicon matt… do you use the mat or
cast without it in order to get the higher temps?
Jim
You can’t use a silicon sill on a vac above 900degrees f… The
rings scorch which prevent vacuum the next time around !! …
Done it to many times… I certainly do not agree that successful
vac is easier to accomplish than centi casting after about 7
years and more books, discussions,etc than can be imagined…
Centi is very, very simple to obtain success and because of the
added force placed on the liquid metal the detail for virtually
the same wax pattern is much better.
Jim
Hi Dan,
Can you cast metals with a casting temperature in the 2200 to
2400 deg F with vacuum casting? Can you cast these metals when
the thickness of the walls of the crown are 4/10’s of a mm? I
really don’t know. For some of these metals I have to put an
extra wind in the casting machine or the casting would be
incomplete. I am really curious.
Regards,
Skip
Skip Meister
@Skip_Meister
N.R.A. Endowment &
Certified Instructor
in all disciplines
Certified Illinois D.N.R.
Hunter Ed, Instructor
Boy Dave, I couldn’t agree with you more about the value of an
electronic kiln controller. I bought the Ney unit, same as my Ney
kilns, about 10 years ago. I can’t believe I got along so many
years without it. My burnout’s are precisely controlled, ramping
up to predetermined temperatures at a predetermined rate and
holding there for as long as I want. I think one of the best
features of these things is the delay start. I can put in my
flasks on Friday at 4:00 PM and set the cycle to turn on at 8:00
PM on Sunday night. So when I get in on Monday morning the cycle
is complete and the kiln has the flasks at the desired casting
temperature. I just love it.
Mark P.
WI
Hey Dave S if you are having such a hard time Vac casting.... give me a call.I did give you my number . I have taken people who have never even Made jewelry and in 2 days got them to cast well enough to start their own businesses... and Its DAN.... Not Don Dan Grandi
DAN: oh damn, I keep screwing up your name, my eyes ain't
that good and a's and o's look too much alike on my
monitor. I think honestly I'll stick with centrifugal for
now. Its what I've invested most of my learning curve in
for several years and I'm only just now starting to get
predictable results and understanding the variables better.
Its also easier for me to load up the crucible and use the
torch with two hands etc.etc. Vacuum casting just
introduces some new variables that I really don't want to
deal with now that centrifugal is working for me better.
Anyway, thanks for your help, I AM using that alloy finally
from United and like what it does. I just got a bead
blaster and having some fun with that. Also I got some
tumbling media for doing coarse and medium cutdown in my
Gyroc which I've never tried. That piece I wanted you to
quote on wasn't accepted by that mail order catalog so I
got pissed off and did a very feminine River Goddess which
is getting a great reaction from women so far just showing
it to the local outfitter store and people in the street.
So it may happen yet, I'll be sending the catalog another
prototype I've done in my tumbler. The weight of the first
piece was too damn much to be profitable but the new piece
is very light. You can see this first piece (the River God)
if you'll go to my jewelry website in my sig below and near
the top the photo is linked to the website for selling
them. The site isn't done yet so only the front page is
working. Once I get some of these other pieces done will
finish the site. Anyway, if this catalog says yes they want
the River Goddess I'll get a quote from you on those and
see where it goes from there. I have no idea what kind of
quantity they deal in yet......Dave --
Crystalguy Jewelry, the first art jewelry site on the net
http://www.opendoor.com/stephensdesign/crystalguy.html Art
jewelry with a mystic touch / Now accepting credit cards
Note: If setting up a "cheap " centrifugal system… don’t
forget that you still need to buy a vacuum sytem for debubbling
the investment.so in actual fact , you can buy the vacuum casting
and investing system for about $700. or less . This is cheaper
than buying an investment machine and a centrifuge. Daniel Grandi
(probably not) The final word on vacuum vs.centrifugal casting.
The best method is the one that I use. I’ve been using it for
many years, have cast many hundeds of flasks and have good
results. Which method is it? It really doesn’t matter so I
won’t say.
My point is this, there are many fine craftspeople who have
excellent results with vacuum and there are also many who have
excellent results with centrifugal. Conventional wisdom is that
vacuum is better for heavier pieces (such as trophy tops) and
centrifugal is better for lighter/thinner pieces(such as a
dental lab would produce). This may be the best rational to
decide where to start but those well versed in their respective
methods have found ways to override these restrictions.
Your actual results are probably more dependant upon procedure
than equipment. Treat it as a science, be consistent in your
procedure, study the outcome and plan corrections for the next
cast. Keep notes. Try to make only one change at a time so that
the results will be indicative of that change only (easier said
than done). Ask questions. Do the answers make sense? Reason it
out. Doubt the advise you’re given (including mine). There is a
lot of voodoo involved in casting.
As far as the cheaper method to get started in…well it depends. Assuming you’re
goal is something beyond a part time hobby and less than a production shop, you’ll
need a vacuum for investing and this can also be used for casting. Perforated
flask is good but there are other ways to achieve the same results (flask liners,
sprue wax inserted into the investment,etc.)
Which ever method you choose, stick with it, learn it and then
IT will be the best way. (Of course you could do both).
Wayne Lenkeit
I gave up on the silicon gaskets years ago. I use the high
temperature graphite gaskets (pg 133 of RIO Tools and Equipment
Catalogue) They are used for the J2r Casting Machines but I have
also used then on my old Kerr Vac-Cast . They last (almost)
forever if you don’t bend them. They don’t like to be bent. I
have also purchased them from Gesswein. They have always given
me an excellent seal.
Darryl MacLeod (Nova Scotia)Hello Donald, I want to say a few things really politely. I
certainely don’t want you to rant at me again just because my
opinions differ from yours. You went out and spent $410.00 for a
centrifical casting machine that many of us feel was not,
strictly speaking, necessary. Although you do not have the
experience many of us have, we still respect your right to do
your work as you see fit. Please allow others this same right.
Do not critize others simply because they are different. This is
an international forum and we must all respect one another. As a
teacher, you should recognize this. Vacume casting is not, as you
stated, a gravity fed activity. Metal is drawn into the cavity,
not pushed as you stated. Vacume is pulling through the porous
plaster from the opening out in all directions. When you pour
liquid metal into the opening, it will fill any void it finds.
That is one way to produce good solid castings. There are
certainly other valid methods. I recall writing an article about
casting some thirty years ago. I wrote that a good way to do
steam casting was to use a potato. It holds a lot of water and
makes a good seal around the edge of the flask. Try it some time.
You can at least eat the potato. Many people, like me, make our
living by producing good jewelry every day. We all do it a little
differently from one another. We are , I believe, right. Think
about it. Tom Arno;ld
… another perspective
For those who say Vacuum it doesn’t work well… can’t be done
…isn’t as good as centrifuge… You folks should see the
factories around here that Have 17 ovens that handle 40 flasks
of 5"x7"size by an average of 70 rings and pendants on each PER
DAY…17 x40x 70 comes to 47,600 pcs per day. from the early
70’s to the early 90’s there were hundreds of companies in this
area that regularly did volumes like this . these mamoth
companies have produced themselves into practical
extinction!!!There are only about 10 left in this area. They did
not die because of bad castings. More like bad management and the
fact that they glutted the market!!! These large companies use
what is called a 4 port flat top vaccum casting table( no
perforated flasks)which will handle 4 flasks at a time! The melt
is done in a hoover gas blast furnace that uses a clay/graphite
composite crucible and will hold around 1,500. oz of
sterling.The melt achieves temp in 30 minutes and they use a
high temp Stainless crucible that is preheated on top of the
furnace to transfer and pour into the flasks. An oven is emptied
in about 40 minutes .Metal is added into the melt as you cast and
melts instantaneously replenishing the furnace as you cast . Now
folks , this is Not rocket science…The ovens are digitally
controlled Just like the small ovens can be. The melts are done
with gas … not with any fancy machines and the quality is
entirely dependant on the skill of the individual caster. The
reason i sugest digital controls is that i do consultation all
over the world for various companies and when they have a problem
and call for a solution… I can give them accurate responses…
when they can tell me the temperatures they are using , the type
of equipment… wether they changed the oil in their vac pumps as
per mfg instructions… what vac level does the machine
achieve… are the silicone pads in good order. These are just
some of the questions that i ask them… there are more. The
bigest problems in casting are usually Not caused by the
machinery being used… but much more so by the operator . If you
are incapable of casting high quality with vacuum or any system
, don’t blame the system… go back to school… or ask “how can
i do it better”. Sincerely Dan Grandi racecajewelry.com
Hi Skip, Yes i have cast metals in that range (2200-2400)…
byrillium , silicone bronzes…Stainless steel…and even did some
platinum a few years ago… in Thailand , we had a metal called
“226” which has a high concentration of palladium. In all of
these, we used the tyvac vac enhancers and flasks that where
scaled to give the optimum vacuum on the pieces being cast. (a
special stainless steel alloy ) is used to cast schoolrings and
has been done on a vacuum caster for the past 15 years.Some of
these metals even require a special investment that has a 2 part
mix and takes 24 hrs to cure.
I’m in the process of moving to a new 4000 sqft building and will
be setting up machinery to do platinum for some of the stores in
the area.I Plan on building a small pressurized vac caster for
this that uses inert gas as the main pressure and deoxidizer. I
have cast some extremely fine filigree work at around 1300oF
oven temp with the metal (sterling )at approx 1950 oF. In the
1980’s… Thin sterling jewelry was “in” and i did literaly up
to10 kilos a week at the factory that i set up for one of my
customers. But extremely thin is not really the norm and is
pretty much useless in the jewelry field.After all, who wants to
buy something that the wind will bend… 15 years of my 30
casting years were spent on a Manfredi high frequency
centrifuge,3 galloni high freq. centrifuges and a german Arno
Lindner machine which used the graphite crucible as the heating
element by directly passing DC voltage into the graphite
crucible. The German machine was the best centrifuge i have ever
seen an used as it not only had the centrifugal action, but the
crucible sat up vertically… the metal was melted and then the
flask was put ontop of the crucible and clamped to the crucible
with a special"hat" . (the crucible had the electricity passed
through it by having a top and bottom plate made of a high
temperature metal where the contacts were made ) the flask sat on
top of this plate. when the melt ws ready(built in Pyrometer)…
you pushed a button and the machine would begin to spin
instantaneously( 2 hp motor pullied downfor torq)when it began to
spin , twin hydrolic cylinders would allow the crucible and flask
to swing downwards very rapidly increasing the centrifuges power
at least 2 times.it used 4" dia x 7 " tall flasks for gold and
silver but really, this machine was designed for Any kind of
metal and did platinum filigree like no other machine. We bought
this machine in 1968 for $15,000 from germany and was very
finicky about which investment was used!!! I wouldn’t exchange
My vac caster for any of them. Sincerely, Daniel Grandi
racecarjewelry.com
Hi! I have already said some things on this topic, but to repeat
as needed, Actually Vacuum casting is using gravity, all the vac
does is remove the trapped air and gasses that are in the flask.
If you think I’m wrong they have these things called books, check
it out for yourself. I am glad I’m not in school anymore. Keep it
Shiny Matt the Catt
Wrong again Dan !!! You dont need a vacuum machine to take out
the bubbles… A vibrating pad from Rio-Grande works real
nice…ROB
Ditto Dan, Hey people this is the 90’s and we’re heading into
the the next century, if yer gonna play with the big kids, " or
make a living, pay your bills ’ EAT! ", your going to have to
play their game their way, not saying spin casting isn’t still
useful,But… vacs where it’s at. I don’t have to years, only
16 or so, as Dan does But I’ve been doing lots of casting, and
both kinds and know what works. I think people who say that
centrifugal casting is better or the only way haven’t tried or
don’t have a vacuum casting system. What it comes down to is time
and money, what making a living is always boiled down to. It’s
also what you comfortable with us humans don’t like change,
especially the older we get or the longer we do something,
Whatever, however, you make it from liquidus to solidus is still
going to be our own personal choice, good or bad. As always Keep
it Shiny, Matt the Catt…