Weekend
Workshop Learning CNC
GoKart Roadster Photography Electronics
PLEASE NOTE. This is an interest of mine, it can be dangerous and will cause serious burns and injury if done wrong. If you feel like trying the same, you do so at your own risk. Please make sure you take all adequate safety precautions.
Please download and read the following
pdf file on foundry health hazards. It is not held locally but in
Australia :-
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After having fun with a charcoal Coffee Can style Foundry, I
decided to build a Propane fuelled Furnace. I have not read any of
the Dave Gingery books mentioned by others, but have found several web
pages giving idea's.
One book I have over here in the UK is "The Backyard Foundry"
by B. Terry Aspin. |
Web pages used for inspiration: -
http://incolor.inetnebr.com/bill_r/fun_with_molten_metal.htm
there was originally more than just this page, but over time the other
links have disappeared.
The metal drum of the foundry is fabricated from a sheet of 20's gauge mild steel. The drum is 12 inches in diameter and 10 inches high. The tuyere hole is 1.5 inch diameter to match the burner. The three metal legs are off an old cooker and the whole lot put together with a small Mig welding kit.
The next stage was the casting of the fire cement. This was done in several stages over a few weeks!
The fire cement, which is good to 1600 degree Centigrade was poured
in the base of the drum up to the level of the tuyere hole, this was
then
allowed to air dry for two days. Next a plastic paint can with an out
side diameter of 7 inches was placed inside the drum. A tube was fitted
through the tuyere hole, pushed up against the paint pot and held in
place
with tape.
( Please note the tuyere hole is not directed at the centre of the
foundry, but off set to the side so that the flame would swirl around
the
crucible. )
This was filled to a depth of 5 inches with the fire cement and allowed
to dry for a day. The pipe was removed and the paint pot lifted out of
the cast bowl. A spacer was fitted in the bottom of the bowl, the
"paint can" put back in place to allow the final casting of the
furnace.
The final height of the chamber is 7 3/4 Inch, giving an internal
volume
of approx. 300 cubic inches.
The assembly was then allowed to air dry for a few days before
using the burner to dry out the cement
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Here the complete bowl is being dried, you can see the water
on the floor, this is being forced out from the base of the metal can.
There is even water on top of the cement as it gets forced out under
pressure. |
| The lid was cast in the top section of a plastic bucket. The
cement is formed approximately 2.5 inches thick, with a 70 mm hole in
the centre forms the vent and sight hole. Most importantly, a metal
frame was cast inside the cement of the lid to hold it all together.
After two days air drying time the lid was then welded with a hinge to
one of the metal legs. After this time the burner was again used to dry
out the lid. Cracks formed in the lid, but the metal frame holds
the unit together well. |
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Using a Salamander A5 Crucible I have melted four and a quarter pounds of Aluminium in 20 minutes. Do not make the same mistake as I did. I left the aluminium to cool and set in the crucible, when I re-heated the pot later the Aluminium split the pot apart.
I managed to check the temperature using a K type thermocouple and digital meter. Got readings of 880 degrees C. If I assume the errors of the meter are all positive, would give measurements of 860 degrees Centigrade or 1580 degrees Fahrenheit. All the above heats used a Bulfinch propane torch.
Starting to work on a new Propane burner along the lines of those
shown on Ron Reils's web pages. Rons web pages have changed over
time so I would suggest if you wish to find information on the burners
that a "google search" is the best thing to try.
30/11/1999 Finished the new
burner!
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It produces a much broader flame then the previous unit. Although it will not stay lit outside the foundry with out the use of an air restricting choke, there is no problem when fitted to the foundry. I did a few simple tests on flow rate and calculated the input in propane gas, as 61,000 Btu or 17.8 KWatt, at a pressure of 1 Bar (14.5psi). |
22/12/1999
On a recent test with a large Propane bottle that did not freeze due to
the amount of gas take off! I measured a temperature of 1100 degrees C
or 2000 degree Fahrenheit. This is still at 1 bar propane pressure and
no forced air. It was hot enough to melt a small lump of Phosphor
Bronze.
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The image on the left is my first try at casting in a mould or casting box, it shows the sprue and in-gate still attached. On the right are my tongs and the crucible holder used when pouring. |
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20/08/2000
It has been some time since I have attempted any castings. I have
up to this point used the foundry to melt aluminium swarf from lathe
turnings and scrap. This meant a reasonable quantity of aluminium is at
hand for small casts!
I am presently in the process of modifying the Champion Mill to CNC
control. (See other pages.)
I needed to put together brackets to mount the 34 frame steppers to the
mill, so I decided to try and cast them.
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The First picture is of the cast metal with riser/sprue and gate, the metal bit on the top is the pouring basin. The second picture shows the original mould with the semi finished part. Note the shrinkage in the metal, due to the 1.5 x 1 x 3.5 inches of solid metal and a badly designed gate system, bad practise! |  |
19/08/2001
Almost a year to the day since I last updated the page! A few weeks ago
I decided to try and melt Cast Iron, a very small lump of about 3/4
lb from a broken Imported vice. After approx. 40 minutes from gradual
heating to full out at about 2 bar propane pressure the metal melted,
this was a great surprise, so I decided to have a go with a larger
amount.
This time I tried 5 lbs of Cast Iron from and un-used bracket off a
Herbert Lathe. Failure, apart from scale no melt, this was tried about
21:00 hrs, the noise from the burner is quite considerable so I shut
the
system down and left it for a while.
20/08/2001
Today I decided to have another go mid afternoon, a bit damp but
outside temperatures a good 18 degrees C. 5 minutes warm up with a
moderate pressure and then full out put from the 0 to 2 bar regulator.
I put a "K-Type" thermocouple through a hole in the side of the foundry
to measure temperature around the crucible, but close to the main wall
of the unit, temperatures of around the 1320 degrees C where being
measured, I then moved the burner either in or out of the tuyere hole
and waited
to see any increase in temperature as I effected the air flow through
the
tuyere, highest reading was of 1350 degree C.
This is not the hottest temperature in the foundry as the crucible
has a more direct heat and after 35 minutes I could break up the Cast
Iron
in the pot with a metal bar.
After 40 minutes the Iron was molten, on lifting the foundry lid, the
heat was tremendous, the crucible was white hot.
The propane gas was turned off and the cast was poured out to form
a small
ingot. At some time in the proceedings the end of the thermocouple
melted
off, the "electrical joint" is still functioning but the steel
protection has gone!
02/03/2003
This is certainly a long time between updates, how time passes.
The foundry has not been neglected all this time, it still gets
used for melts. Generally I use it to form ingots from scrap
either in
Aluminium or Brass. In the past few days two Brass melts were
done
of 10 lbs each. The metal was poured into a simple open mold made
from
a 4 inch pipe welded onto a steel plate. The mold has been
de-burred
to allow the solidified metal to just fall out. The following
images
shows basic progress through one of these melts.
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<=This is the equipment prior to the start of
the melt. The pot is charged with scrap, the tongs, pouring ring,
mold, and temperature meter off a K-type thermocouple all ready. This stage is near the end of the melt, the crucible has been repeatedly filled as the scrap melts and the metal is just below the rim of the pot. Temperature on the meter is around 1100 degree C => |
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<= This is just after pouring the brass is in
the mold and the cooling starts, the plate of steel next to the mold
was
placed on top to reduce the amount of air to the metal during
solidification. The metal tipped out of the mold, note the colour banding? => |
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<= This picture is after machining in
the lathe to remove the outer surface and many, but not all
irregularities. Final diameter of this brass bar was 3.95 " by
2.1" long. A little while later and a section of the brass has been bored to suit available bearings and parted off to 700 thou. This will be used to form a Worm driven gear wheel, if all goes well? => |
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One thing I find to be quite satisfying, is that the foundry has
lasted well for over six years, and still looks as though it has
plenty of use left in it. It is unlikely I shall use the unit for
cast Iron again unless there is a specific need to do so, it was not
designed with that in mind. But it does show what can be done
with a simple burner design and without forced air flow.
All the melts and pours up to now have been either just to produce
Ingots or as above with a specific machining task in mind. I will
admit I have vary little imagination when it comes to art
objects. One day I will try, but not for now!
For North West UK viewers, who have an interest in this as a hobby and
need to obtain the foundry materials, have a look below.
Engineering and Foundry Supplies
(Colne) Limited. These people have been extremely friendly and
helpful.
They can supply sand, refractory cement, crucibles, ladles, fluxes,
etc .etc. etc. My own contact has been a Stephen Frost, one of the
Directors of the company. The telephone number is 01282 868411. Fax
number is 01282 867545
They also have a web page at http://www.ef-supplies.co.uk
Keith Prosser Castings.
Barnmeadow Lane, Great Harwood, Blackburn. Lancashire.
Again I find that helpful advice goes a long way. When finding out
about casting, I contacted Keith and was invited to visit his foundry.
Keith specialises in Aluminium casting for both artistic, structural
or standard products.
Having seen pictures of their work I would certainly say it is well
worth a call if you are in need of any aluminium casting done. Tel/Fax.
01254 876402.
The casting or moulding boxes came from a company called Fulworth Engineering.
Their address is Atley Works, Dalton Lane, Keighley, West Yorkshire
BD21 4HT
Tel. 01535 665188 and Fax 01535 610186.
The contact I have is a John Shackleton. email address is
fulworth@hotmail.com.
They have a web page at .http://www.acetarc.co.uk/html/fulworth.html
The company deals in used foundry plant and equipment, mostly for
commercial companies, but the casting boxes are the same for all.