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Nitrogen and wax injection


#1

John, Where does one find compressed nitrogen? I assume it is in
a tank like oxygen??? How do you hook it up? Thanks, Deborah


#2

HI Deborah, You get the Nitrogen at your welding supply house.
You will need an inert gas regulator. Sometimes your supply house
will have a rebuilt one for much less than new. Set the regulator
5 or 10 lbs. above your normal injection range. You will need
enough hose to reach from where you store the tank (could be
almost anywhere) to the regulator on your injection pot. At the
end of your injection run, merely turn off the tank but don’t
bleed the line so the wax can be covered with Nitrogen. Don’t
forget to chain your tank to the wall. Any pressurized tank
could be a missile if the valve were knocked off! Depending on
how much injection you do you can choose from variety of tank
sizes. We do lots and lots of injection as we are a production
casting house. We use the largest tank (about 4 1/2’ high)and use
3 or 4 tanks a year. John, J. A. Henkel Co., Inc. Moldmaking,
Casting, Finishing


#3

Nitrogen and Wax injection… hummmm… Ok, 6 months ago , i
bought a nitrogen tank , regulator and assorted clamps and
fittings and hooked up the whole thing to a wax pot that was
originaly setup on compressed air.I was getting some airpockets
in the waxes and it was suggested that the airpockets were being
caused by the compressed air ( due to condensation in the air
lines and water getting into the wax). In a previous factoryabout
2 years ago, we had a similar problem and bought a $4000 air
purifier and dryer system … thinking that this would solve the
Air bubble problem. We had already tested wax temperature with
digital thermometers and the wax was at the recommended
temperature . The purified /Dried air did not eliminate the air
problem. Using a lot of powder did eliminate the air pockets,
but left a rough looking wax. The airbubble problem would appear
and disapear (humidity/ barometric pressure Seemed to have a
great effect on the wax.) I bought the nitrogen to absolutely
rule out the posibility of water condensation being the cause of
the air pockets.We still had Airpockets…!!! What finaly
resolved the problem for us was at the end of the day, we would
add wax to the pot… then raise the wax temperature from 150
oF to 170 oF and leave the waxpot at the higher temperature for
3 to 4 hours (even overnight) . It is important to leave the top
of the pot slightly Ajar so that whatever air/ bubbles are in
the pot Can escape.After reaching the higher temperature, we saw
air bubbles climbing up slowly through the wax and busting on
the surface.This would continue to happen for at least an hour
and then the bubbles would stop surfacing. At this point we
could lower the temperature back to 150 oF and resume injecting
our waxes.PRESTO ! No more airpockets in our waxes. What the
nitrogen does do is offer a good , quiet source of Pressure for
our wax pots Our tank of nitrogen is still more than 1/2 full
after 7 months of waxing on 2 wax pots. ( probably 50, 000 waxes
or more) We installed a shut off valve just before each wax pot
regulator so that the nitrogen could be shut off at the waxpot
when we wanted to fill the wax pots with more wax. Hope this
helps some people … Daniel Grandi
http://www.racecarjewelry.com visit the workshop on the
web !


#4

Hi Deborah,

Most compressed gases are available from welding suppliers. The
use of any bottled, compressed gas requires the use of a
regulator to drop the pressure form that existing in the tank to
the pressure required by the using device.

Connecting a wax pot to a regulator on a nitrogen bottle can be
accomplished using a hose similar to a welding hose. The fittings
on the ends of the hose should match those of the regulator & wax
pot. The fittings on the wax pot end are dependent on the type of
pot being used. The hose could be replaced by copper tubing if a
permanent installation was desired.

Dave


#5

Hi Dan et al, A word of caution. Raising the wax temp above the
suggested temp will shorten the life of many types of injection
wax. It is also important to differentiate between bubbles in the
wax and air trapped inside the mold during injection. Powder used
sparingly on your molds is a good problem solving tool. It does
more good on the inside surfaces of the mold where it separates
than the actual surface of the pattern. John,J.A.Henkel Co.,Inc.
Moldmaking, Casting, Finishing


#6

Hi John, We are very well aware of the above… but i’m letting
you know that what i had previously described as a method of
fixing the airbubble problems does work . Nitrogen did nothing
but make a quiet air system which is a good thing. Daniel Grandi
http://wwwracecarjewelry.com