Dear Mr. Wadia, I was skimming the ganoksin web site and found your
response regarding Memco verses other casting machines and I wanted to
write you for clarification on some of these issues. I find some of
your points very interesting starting with your opinion that ceramic
crucibles and forming gas are a better “system” than any other truly
closed system-casting machine using an inert gas for protection. As
the ceramic crucibles are four to five times the cost of the graphite,
yet do not have four to five times the life, I am uncertain how this
can be of any advantage. I constantly hear from uninformed people that
graphite inclusions are found on pieces from machines using graphite
crucibles, however this is highly unlikely, (unless you are using an
inferior material). As any graphite (or carbon) that might remain in
the melt “floats” on the surface and rises to the button, it is next
to impossible to have graphite inclusions on the pieces. Also due to
the extremely high melting temperature of graphite, it is also very
unlikely that the graphite would meld with the material you are
casting with. More on this subject can be found in the Santa Fe
Symposium available through Rio Grande. You may want to
go to this, as it is very informative and there are many industry
experts much more knowledgeable than I am. The last point I would like
to make about the graphite crucibles is that they actually do serve a
purpose. The graphite will scavenge any remaining or trapped oxygen
from the metal during the melting process and provides chemical
reduction of metal oxides. You do not get that with ceramic
crucibles. Bottom pour crucibles have been around much longer than
Memco has been producing machines. As a matter of fact, most of the
original machines manufactured long ago used this same principal, so I
did not understand the comment of Memco’s crucibles now being
regularly copied.(?) If I am not mistaken, the thermocouple on the
Memco does slide down into a tube that is placed in the crucible, very
similar to any other bottom read system. However, I do not understand
how the Memco measures the temperature so accurately when it uses an
archaic control unit. As a test on a Memco, or any machine for that
matter, use a quick read pyrometer and a direct dip thermocouple on
various melts and see how close the temperature is to the controller
on the machine. I have done this on various machines, (including
Memco) and have yet to find one that is as accurate as the Neutec/USA
machines.
You then discussed some points that I also find intriguing. 1. The
first was you recommend leaving 1 �" of bare center sprue toward the
button on your tree, as your current machine is not able to
completely fill to the button. I am assuming your point is that the
metal begins to freeze before it gets to that part of the tree, thus
you feel you must leave that space free of pieces. I understand that
Memco’s temperature control is as I said before, somewhat archaic
however this is a great “waste” of metal, as you must fill all the
bare area as well. When using the Neutec/USA machines, and the
NeuSprue treeing system, you can sprue nearly to the button, (which
contains less metal than the traditional main tree button) thus you
have more product with better fill and less “scrap” per cast. This
cuts the number of trees daily, which in turn saves in investment as
well as metal in process, and you don’t have as much “used” metal to
deal with. Because you use less flasks, there is less labor cost built
into each cast and the savings goes on and on, yet we can discuss that
later if you would like. 2. You suggested SLIGHTLY overheating the
investment to help with fill. There are arguments both ways with this
however I personally prefer to increase the metal temperature (if
either), as the flask retains the heat longer, which can create other
issues. 3. The size of the holes in the perforated flasks may not be
as critical as how well they are placed and the sheer number in each
flask, and there are other key points , which I am sure you are aware
of. Even with a “lowered” vacuum, a 30 second draw down time is more
than sufficient to completely evacuate the gases to allow for little
resistance in the metal flow into the flask. Keep in mind; investment
even under a vacuum takes at least a few minutes to cool in the area
around the pieces. 4. I find it interesting that Memco has different
crucible hole sizes for different alloys. You say the purpose is to
control the flow rates yet most other machine manufacturers recognize
that the metal will flow at a certain rate unless it is placed under
pressure and there is no need for different size holes for different
alloys. Neutec has two different crucibles with different hole sizes
however this is only for the different tree size one might use. 5. Your
point five is where I am in total agreement with you. There are so
many alloys to choose from and it is sometimes very difficult to find
a reliable material for all your patterns. It is a trial and error
situation however the right casting machine with accurate temperature
control can definitely take some of the guesswork out of it. 6. Forming
gas? Does it not make more sense to have the entire melt and pour
area completely oxygen free as most of the advanced technology
machines are doing these days? And pushing a forming gas over the
surface of the metal does not completely eliminate the oxygen that is
trying to attack your melt as well as, what exactly does the forming
gas do to help you get porosity free castings? I have yet to see a
better finished casting due to any type of gas or other influence in
that area. Also, using two different gases, storing two different
tanks and /or using a gas mixing unit seems like a lot of hassle for a
relatively un-leak proof system. Neutec’s closed system approach is
unsurpassed in reducing or eliminating oxides from the melt. 7. You
mentioned this earlier however I would like to ask that you explain to
me (as I truly do not know) what the advantage is to having a vacuum
pump achieve a maximum of only 25" of mercury. That seems to defy all
logic when casting jewelry on any type of machine. I look forward to
your response on this subject.
Now when we talk about speed, I know that Neutec machines have the
fastest flask-to-flask time cycles and are the most controlled
machines in the world today. I have spoken with customers that are
producing up to 30 flasks per hour without any down time and because
the Neutec J-Series machines auto-cast, one operator can run two
machines; imagine the savings that creates. Even the J-2R can cast a
flask every 6-8 minutes and can run all day without any "cool down"
period, and the new J-z is a manual cast unit that can out produce
many machines costing two and three times it’s cost.
I look forward to your response as there are a few very interesting
points that you brought up and I would love to get some feedback.
Please feel free to contact me at my mail address so that we can
discuss these points further.
Regards, Joe Lovato
