Thanks Jeff,
Going to hang in there and try some of the things suggested… still talking
to Gavin in understanding how to cast using the perforated flask… however,
Everyone suggest you, ‘CAST AT THE RIGHT TEMP’ . . well, when using a torch
and crucible other that just looking at the melt; movement, shine, way it
rolls, ???
… which does’t tell the temp . . who do you know other than experience??
In Tim McReights book on casting he says to cast the metal after it looks
like liquid mercury and THE SURFACE STARTS TO SWIRL ON ITS OWN A LITTLE. I
wonder if this is valid advice? Some of Tim’s advice seems wrong, for
instance in the Complete Metalsmith he advises using an old dryer motor for
a buffing motor. Well, it works but he neglects to tell you that dryer
motors have an auto start feature so when you pull the motor and plug it in
it doesn’t work unless you manually start it revolving or it burns out. I
for one get pissed off at such incomplete descriptions that cost me alot of
time and almost spent 60 bucks on a union electrician to tell me why the
motor didn’t work. So, is the advice to cast when the metal just starts to
swirl BS or what? Dave
Art Jewelry for Conscious People
http://www.opendoor.com/stephensdesign/crystalguy.html
Different alloys behave differently, one of these days, you’ll begin to
sense the color of the heat. The new silicon alloys don’t roll very
much, they just kind of sit there. They also require more heat than the
non-silicon alloys. If you under-heat silicon alloys you’ll stand a
chance of porosity, and possibly prongs cracking a year down the road,
This has happened to me on several hundred castings (At one point I was
casting 200-300 pieces a week). Boy, we couldn’t figure out why the
prongs where snapping a year after the piece was delivered. After a
BUNCH of research, I learned this, both flask and alloy temps need to be
increased about 100 degrees F. to avoid porosity and possible cracking
in the castings at the extremities of the flask where the temp is lower.
I began casting large flasks (centrifugal) at 1100 - 1150 F and heating
the gold to about 1750 - 1800 F. Then the castings started coming out
perfect. I began to lose a little bit of my dislike for those darn yucky
silicon alloys. The only good thing about them to this day is that they
cast fairly clean.
I stick to a few favorite alloys because I know their characteristics,
and how they cast, and I like the finish color, and for my personal
casting work, I do not use silicon alloys! :).
Jim Chambers wrote:
Everyone suggest you, ‘CAST AT THE RIGHT TEMP’ . . well, when using a torch
and crucible other that just looking at the melt; movement, shine, way it
rolls, ???
… which does’t tell the temp . . who do you know other than experience??
Jeffrey Everett
Handmade 18K, 22K, and platinum gemstone fine jewelry.
Diamond setting, rubber/metal molds, casting, lapidary
Die and mold engraving, plastic patterns for casting.
Cad jewelry design, cad/cam milling scroll filigree…
P O Box 2057 Fairfield IA 52556 515-469-6250
Dave Stephens wrote:
Thanks Jeff,
Going to hang in there and try some of the things suggested… still talking
to Gavin in understanding how to cast using the perforated flask… however,
Everyone suggest you, ‘CAST AT THE RIGHT TEMP’ . . well, when using a torch
and crucible other that just looking at the melt; movement, shine, way it
rolls, ???
… which does’t tell the temp . . who do you know other than experience??
In Tim McReights book on casting he says to cast the metal after it looks
like liquid mercury and THE SURFACE STARTS TO SWIRL ON ITS OWN A LITTLE. I
wonder if this is valid advice? Some of Tim’s advice seems wrong, for
instance in the Complete Metalsmith he advises using an old dryer motor for
a buffing motor. Well, it works but he neglects to tell you that dryer
motors have an auto start feature so when you pull the motor and plug it in
it doesn’t work unless you manually start it revolving or it burns out. I
for one get pissed off at such incomplete descriptions that cost me alot of
time and almost spent 60 bucks on a union electrician to tell me why the
motor didn’t work. So, is the advice to cast when the metal just starts to
swirl BS or what? Dave
Art Jewelry for Conscious People
http://www.opendoor.com/stephensdesign/crystalguy.html
orchid@ganoksin.com
Dave,
All things considered the temperature of the metal is not all that
important.In large production shops yes it is where 100 or more items
are cast in one large flask but for a guy that casts a couple of things
in a home shop no it is not.
Basically if the metal is giving off fumes or smoke it is either dirty
or too hot…Remember that gold alloys do appear differently than the
sterling will.It is like soldering and you get the feel of it after a
little practice…If you can stir the entire melt with a carbon
rod(cost about a dollar from most suppliers) and the crucible is well
heated around the inside of the nipple then you can cast…Any further
heating is a waste of time and fuel.The use of the carbon stir rod is
good as the carbon expels any of the oxygen absorbed and the reason is
some complicated carbon monoxide formation chemistry but basically the
carbon rod generates carbon monoxide by converting the oxygen to carbon
monoxide which has a good instead of harmful effect. …Gavin
Jim,
Action Mining fax 702-367-9623 sells a digital probe that you can
just stick the end of into the molten metal and read an accurate
temperature or at least they did last time I checked.These things are
about $120 but you can use it for the furnace temps also.
As to vacuum vs. centrifuge I say each has drawbacks but with a lot
of patience and some practice either one will work well…It is not the
casting equimpment that is the cause for many failures but rather the
spruing or investing or burnout…In short either vacuum or
centrifuge systems are only as good as the person operating them and
with experience it is not too difficult to produce good castings with
either…Gavin
Jim Chambers wrote:
Gavin,
You Wrote,
crucible is well heated around the inside of the nipple
Is this the point where the metal will exit or at the bottom of crucible!!
Jim
At 12:04 AM 10/14/96 -0500, you wrote:
Dave Stephens wrote:
Thanks Jeff,
Going to hang in there and try some of the things suggested… still talking
to Gavin in understanding how to cast using the perforated flask… however,
Everyone suggest you, ‘CAST AT THE RIGHT TEMP’ . . well, when using a torch
and crucible other that just looking at the melt; movement, shine, way it
rolls, ???
… which does’t tell the temp . . who do you know other than experience??
In Tim McReights book on casting he says to cast the metal after it looks
like liquid mercury and THE SURFACE STARTS TO SWIRL ON ITS OWN A LITTLE. I
wonder if this is valid advice? Some of Tim’s advice seems wrong, for
instance in the Complete Metalsmith he advises using an old dryer motor for
a buffing motor. Well, it works but he neglects to tell you that dryer
motors have an auto start feature so when you pull the motor and plug it in
it doesn’t work unless you manually start it revolving or it burns out. I
for one get pissed off at such incomplete descriptions that cost me alot of
time and almost spent 60 bucks on a union electrician to tell me why the
motor didn’t work. So, is the advice to cast when the metal just starts to
swirl BS or what? Dave
Art Jewelry for Conscious People
http://www.opendoor.com/stephensdesign/crystalguy.html
orchid@ganoksin.com
procedures
WOW! Lota bucks!! Is it worth the Bucks, I pour using the following;
characteristic; Metal is puddling, rolls together, shinny, remove flame and
puddle wholes for about 5/10 seconds(never timed it)??
First I’m going to try a couple of the things suggested Paper seal with temp
grease, etc,
MY vacuum has a canister(hole… with vacuum point inside), I have several
round aluminum covers(tops) …2 types with silicon gaskets on the under
side. They fit in the rim of the cannister(standard Vigor, blue machine),
One aluminum cover has a hole in the top, a little larger than a pencil… I
place the cover, gasket down on top of the cannister with a silicon
'pad(there is also a silicon gasket under the cover which seals the vacuum
cannister(is about 4 inches across) on top. . I place a NON-perforated flask
on top of the silicon pad covering the cover with the pencil sized hole on
top of the silicon pad and POUR!. . a surface pour… the pad also has a
pencil hole!
The second cover has a much larger hole, bout 3 to 4 inches across… I have
Perforated flask that fit exactly into the hole … these flask have a
flange around one end about 1/2 inch from the bottom, SO when I place the
perforated flask through the large hole in the cover and down into the
cannister, the perforated flask, due to the metal flange around the bottom
holds the flask up above the aluminum cover for about 1/2 inch… I
HAVE NEVER TRIED TO POUR IN THIS MANNER … DON’T KNOW IF THIS IS THE
CORRECT WAY TO USE THE EQUIPMENT …
Really want to try to do a perforated flask pour … instead of a what I
term a … surface pour … does this sound correct…???
Jim
At 11:48 PM 10/13/96 -0500, you wrote:
Jim,
Action Mining fax 702-367-9623 sells a digital probe that you can
just stick the end of into the molten metal and read an accurate
temperature or at least they did last time I checked.These things are
about $120 but you can use it for the furnace temps also.
As to vacuum vs. centrifuge I say each has drawbacks but with a lot
of patience and some practice either one will work well…It is not the
casting equimpment that is the cause for many failures but rather the
spruing or investing or burnout…In short either vacuum or
centrifuge systems are only as good as the person operating them and
with experience it is not too difficult to produce good castings with
either…Gavin
Jim Chambers wrote:
Thanks Jeff,
Going to hang in there and try some of the things suggested… still talking
to Gavin in understanding how to cast using the perforated flask… however,
Everyone suggest you, ‘CAST AT THE RIGHT TEMP’ . . well, when using a torch
and crucible other that just looking at the melt; movement, shine, way it
rolls, ???
… which does’t tell the temp . . who do you know other than experience??
Jim
At 01:11 AM 10/11/96 -0500, you wrote:
HI all
I’m somewhat amazed that in this extensive thread, the fundamental
differences between vacuum and centrifugal casting have not come up.
I would first like to say, THEY BOTH WORK VERY WELL!!! And I might add
that most of the professional casting shops I have worked in use vacuum
casting. They basically boil down to knowing the correct temperatures
for the metal being cast, and spruing the piece properly.
As a casting professional, I must say that you have to know what you’re
doing to get good results, and long experience is a great teacher. It
took me YEARS of problem solving to REALLY understand what goes on when
the metal is poured or injected.
Jeffrey Everett
Jim Chambers wrote:
Worth 1 cent . . . not two;
Started with Vacuum … as an amateur . . I continue to consider myself as
an amateur probably due to casting techniques and as one would, have tried
many, many ideas, methods, suggestions to very little added success. . .
most local "business professionals, casting for as a corporations have
suggested that,
- " Detail is lost with vacuum!" . . . spelled ‘Quality’
- " Readability, forgiveness, in method is lost with vacuum!"
… GET RID OF IT!!! …
THAT’S WHY I LOOKING FOR A CENTRIFUGAL!
C U R R E N T P R O B L E M S WITH 'MMYY' VACUUM PROCESS!
Instruction which came with the unit(most popular brands carry
basically the
same ‘blue’ , ‘multi buck unit’)
-
Equipment documentation suggest that the silicon pad scorches
at 900
degrees. Investment break down between 1250 and 1325 . .considering the
problem presented by porosity at higher temp, in that silver melts at
16++/17++ depending on quality . . there is a ingrained problem…
( And I've had/have them all . . requires more control than
the less
auto-equipment.
-
Absolute prefect surface is required relative to the bottom of the
flask being cast… drop an empty flask and you can either through
it away or file the bottom for an hour to remove the dent… a
break in the vacuum!
-
Slightest 'scorch/ring in the pad( $20.00 A pop!) will prevent the
vacuum from taking Place! . . . NOW WHAT ABOUT THE MOLTEN SILVER(Watch
that temp!), cylinder getting cold( greater difference in silver temp
and cylinder Temp spelled porosity!.
-
Vacuum allows doubt as to success with pour . . Vacuum often
doesn’t
Gavin,
Thanks, I pre-heat the crusible particular the bottom. . prior to pouring
the metal, I heat the crusible exit point . . but not to a ‘red’ hot
temp… I’ll try doing that in the future…
Jim
At 12:47 AM 10/18/96 -0500, you wrote: