Home Foundry

by magicman391

143K24118

Intro: Home Foundry

This instructable will take you step by step how to make a home foundry so you can make quick and efficient aluminum melts for casting. Its propane fueled so its easy to set up and easy clean. I hope it's informative and allows you to make castings of your own. This instructable is a result of my own research and trials I hope it benefits all those who wish to follow into the world of the home foundry.

This not the cheapest furnace but i had to buy a lot of my supplies. If you are a good scavenger/bargain hunter then your total price will be less than mine. Also propane compared to other fuels isn't the cheapest either, but it is clean and efficient.

Warning/Disclaimer: Working with molten metal is extremely dangerous. I do not claim any responsibly for any injuries or accidents that may occur during replication of this instructable. Always be safe when working with high temperatures and molten metal (don't do anything stupid and always wear safety equipment).

Do plenty of research and know what your getting yourself into.

Some references:
http://www.backyardmetalcasting.com/index.html
http://www.engineeringtoolbox.com/melting-temperature-metals-d_860.html
http://www.youtube.com/watch?v=lX6yFQNnk-A (this a charcoal foundry but there is still much to learn from it)
http://www.youtube.com/watch?v=B5wCVI7jCyQ&feature=related
https://www.instructables.com/id/My-Second-Aluminium-Foundry/step4/Refractory-Support/

STEP 1: Materials

Materials needed:

Burner:
   -1/8" hex cap
   -1/8" pipe (i used brass but steel would be better)
   -1/8" to 3/8" brass fitting
   -3/8" to 1/2" steel fitting
   -1/2" steel pipe x3
   -1/2" T pipe
   -1/2" valve
   -1/2" npt to 3/8" nptf fitting
   - 1/2" to 1/4" reducer fitting
   -1/4" x 2" pipe
   -1/4" ball valve
   -1/4" male quick disconnet
   -3/4" steel pipe about 7" long
   -Gas hose
   -High pressure valve

Refractory:
   -Portland Cement (crucial that its portland not masonry)
   -Silica Sand
   -Perlite (used in planting it is an aerated volcanic rock that doesn't absorb heat readily)
   -Fireclay (i had no supplier of this but i used rutland refractory cement instead)
   -Water

Furnace in general:
   -Steel pots or pails (avoid galvanized apparently if they get to hot the zinc on them will release toxic fumes)
   -1" id Steel pipe for burner inlet
   -Drainage pipe about 2" long (leftover from making the burner inlet)

Crucible:
   -Scrap sheet metal
   -Scrap rod of various sizes (i used 1/4 and 1/8)

Various:
   -Steel rod
   -Cardboard
   -Gaffers or duct tape
   -Teflon tape
   -Mixing tub
   -Propane tank
   -Set screw

Safety equipment:
   -Welding Gloves
   -Safety Glasses
   -long pants
   -flame retardant shirt or jacket

And of course lots of scrap aluminum to melt

STEP 2: Tools

Tools needed:

Dremel
Various bits for said dremel
-cutoff discs
-sanding drums
Sharpie
Paint auger
Respirator
Wrenches
Lighter
Cupcake pan
Air Compressor
Drill
Beating stick
Welder
Metal forming equipment (nothing major)

STEP 3: Burner

Start with the gas line:

Take all the parts for the burner assembly and wrap the threads in the teflon tape.

-Assembly starting from the tank end to the actual burner:
   -attach the high pressure valve to the propane tank
   -connect the gas hose to the high pressure valve
   -next is the 3/8" nptf to 1/2" npt
   -then 1/2" x 2" pipe
   -then a 1/2" ball valve
   -followed by another 1/2" x 2" pipe
   -next is the T pipe
   -on one side yet another 1/2" x 2" pipe follows
   -the following part is the 1/2" to 3/8" fitting
   -then the 3/8" to 1/8" fitting
   -next is the 1/8" pipe
   -on the opposite side of the T pipe is a 1/2" to 1/4" reducer fitting
   -then there is a 1/4" x 2" pipe
   -followed by a 1/4" ball valve
   -and lastly attach the 1/4" male quick disconnet

Before placing the hex cap on a few things need to be done.
   -a very tiny hole needs to be drilled in the 1/8" pipe (as small as possible) this hole must be facing as straight down the blower pipe as possible
   -take the 3/4" pipe and drill a hole in the side so it can slide on the 1/8" pipe
   -also drill two 3/8 holes into the top of the pipe

once the 3/4" pipe is slid onto the 1/8" pipe screw on the hex cap
next a set screw is need to keep the pipe form sliding or moving around
   -align the tiny hole in the 1/8" pipe centering it down the 3/4" pipe
   -screw the pipe in place (be careful not to puncture the 1/8 pipe
   -i used epoxy putty in addition to make sure it doesn't move

STEP 4: Crucible

This i did at the shop at my school.

I took a 16 gauge steel sheet and cut it to about 5 inches high
next i rolled it to 4 inches in diameter and welded the seam
i plasma cut a base and welded that to the cylinder i just made

make sure the welds make a seal (it would be bad if molten aluminum leaked all over your furnace)

the main chunk of the crucible is made at this point but i had to think how i would lift it out and pour

i added two lugs (one on either side) which allows me to pick it up with the tongs i made
i also added a half ring on the bak to allow me to tip the crucible while i have it picked up

STEP 5: Furnace

Take the two pots or buckets and decide the top and bottom.

Find wether it be big cans or whatnot to make the inside forms out of. you want them to be big enough that you can easily fit your crucible inside but not to big that there is a lot empty space

Burner inlet:
   -cut a pipe that allows the burner to slide in perfectly it should be just long enough that it goes into the furnace but allow the burner to have the holes exposed
   -cut a rod and bend it slightly as a support for the burner, weld this to the inlet pipe

Top:
   -on the top cut a hole the size you want the opening to be (i made mine the size of a can because it was easy to acquire form to wrap the cardboard around)
   - make this about the height of a can
   -find a bigger form to wrap more cardboard around to get the main form cavity
   -tape the opening cavity to the pot
  - leave the bigger form for when you start parking in the refractory

Bottom:
   -cut a hole in the bottom the size of the drainage pipe you made/acquired
   -tape that down
   -make a form the same size as the big one in in the top part (again wait to put in until you start adding the refractory)
   -on the side pick a place to cut a hole for the burner inlet
   -tape the burner inlet pipe in place

STEP 6: Refractory

The refractory is probably the most important part of the project. This is because it not only keeps the keeps the heat from burning the surrounding area, but it also keeps the heat in the furnace which allows it to be more efficient.

While mixing prior to adding water wear a respirator the dust is nasty to breathe in.

To make the refractory:
-Use a 1 gallon bucket to measure the ingredients
-The mixture is made of:
   -2 parts sand
   -1.5 parts portland cement
   -1.5 parts perlite (amount i used but more won't hurt since it does a really good job of keeping the heat in the furnace)
   -2 parts fireclay or refractory cement
   - Just enough water to keep the material clumpy (when there is extremely high heat involved you don't want too much water in the refractory (heat and trapped water don't mix well... boom))
- Steps to mix:
   -in the big mixing tub pour the portland, sand, and perlite
   -i used 2 gallons sand, 1.5 gallons portland, and 1.5 gallons perlite
   -Mix with the paint auger and add some water to it (just a little)
   -Next add the fireclay/refractory cement
   -i used 2 gallons of it
   - Mix all together and add more water till it clumps together (avoid soupy)

Once the refractory is mixed:
-Use your hands to pack the material in as tightly as possible (avoid any air bubbles)
   -I used a 1-1/4" rod to help pack the material in
-When filling, pack the material around the parts that are taped down (ie. the drainage pipe and the opening form)
-Once level with them place the bigger forms in and pack the material in tightly around it.

I had extra refractory so i made two plinths that the crucible can sit on as well as a block that i can place the castings on when i pour.

STEP 7: Finishing Up

After about 2 days from mixing, the refractory should be solidified enough to take out the forms.
-Do this carefully so as not to damage the walls

After about 4 days from mixing the refractory should be ready to be fired.

STEP 8: Firing Up

To fire up your newly completed furnace place the top part on the bottom part
-Next hook up the gas system (i.e. blower to both the propane tank and the air compressor)
-Place blower into furnace entry
-Turn everything on
-Adjust the high pressure regulator to about half way (in other words turn the knob several turns to crank up the pressure)
-Slowly turn the gas ball valve and light with your lighter and adjust the flame
-Slowly turn the air ball valve to make the torch
-Play around with both valves until you get a decent torch
-Wait about 15 minutes (to condition the refractory) then turn off the ball valves

Now for a melt:
-In the bottom part of the furnace place a plinth and your crucible
-Put some scrap aluminum in the crucible
-Repeat the steps above (except the last one)
-After about 15 minutes the metal should be nice and melted continue to place scrap in for another 5-10 minutes until full
-Finally turn everything off
-Take off the lid
-Lift the crucible with the tongs
-Pour the liquid metal into any molds you have made or into cupcake pan

STEP 9: Results

Here are some of the ingots i got from my furnace using the small cupcake pan.

STEP 10: Video

STEP 11: The Future

In the future i plan on making an instructable on casting with multiple materials.

There are many different types of casting and casting methods.
Just to name a few:
   -Lost wax
   -Green sand
   -RPM (rubber plaster mold)
   -Lost Foam

18 Comments

apope8 8 years ago

Hey,

I love this build and will likely be doing something along these lines myself. However I am honestly very confused about the last step in Part 4. So I drill the tiny hole in the 1/8th pipe for the air and propane to blow through? And if that's the case how is the drive screw securing the 1/8" without puncturing again. Or is the tiny hole to insert the drive screw into to secure the pipe. In either case I'm not sure I understand how the propane and airflow is going through to side of the 1/8th inch pipe into the 3/4 inch to cause the flame (even through a tiny hole).

SammyPati 8 years ago

I also want to build one of these, I was at a 'Lost Skills ' fair a few weeks ago and struck up a conversation one of the Blacksmiths that was demonstrating his skills. I mentioned wanting to build one of these foundries and he recommended using a Coal fired one. He said the gas ones are very dangerous if they are not done correctly.

Apparently they need a back pressure valve or something t?

Anyway one of his friends had a fan (hair dryer) blowing into the flame to increase the heat and it overheated and switched off. Somehow the sudden drop in air pressure caused the flame to back pressure in to the pipe and it exploded.

I'm not sure if he was pulling my leg or of its a real possibility.

Does anyone know about this?

I checked the instructable but didn't notice anything mentioned about how to avoid it.

zjnolan 8 years ago

I was just curious how your refractory mix has held up over the years? I'm looking to improve my foundry with a mix. I appreciate your investigations.

434DeathHammer 9 years ago

I have an assortment of scrap metallic objects in steel, iron, copper, brass, aluminium, nickel, etc that I will one day melt down and produce an ingot of it. Would it work for that?

ronivan.fontanez 9 years ago

I have a question: it only uses propane and air to melt aluminun. It don't require the use of charcoal. I'm making a furnace and I don't want to use any coal, just air and propane.

jamesstalker 10 years ago

Have you attempted Brass with this one?

Kjetil Egeland 10 years ago

Great job...! You gave me an idea now..... hm.... :)

Kjetil

wurkyman 11 years ago

you might want to reasearch induction heating.

x3wayassassin 11 years ago

The blower is not really needed unless you were using natural gas or charcoal. propane is already under pressure when it comes out of the tank. just to let anybody no. Great job.

TheReplicaz 11 years ago

Thanks for posting this!
But, why do I need a drainage pipe at the bottom of the foundry?
Please, reply.

malleolus 11 years ago

If the crucible you use melts through, the drainage pipe keeps you from ruining the entire foundry, only the bottom.

pyrogreasemonkey 12 years ago

replace pearlite with foam beads, such as from packaging. foam will burn out and makes better insulation, but pearlite melts if you do anything hotter than aluminum melting. portland cement becomes a flux at relatively low temps in a furnance and holds chemically bonded water. use fireclay, sand, foam, and crushed firebrick if you can find it. about 3.5 parts clay by weight, 1.5 parts sand by weight, 3 parts crushed firebrick, and then you want to have about 50% of the refractory as a whole to be foam by volume. first mix together the foam, sand, and crushed brick with a small amount of water. then add the fireclay. mix well. you want to use as little water as posible because clay shinks as it dries. that is the same reason you want sand and crushed brick, it keeps the clay from shrinking and cracking a lot during drying and curing. the first time you fire it, start by making a small charcoal fire in it and then after a few hours turn on the propane to get the clay to sinter. the clay must get as hot as posible for as long as posible, but raise the temp slowly so the water gets cooked off slowly

Mr. E Meat 13 years ago

Do you need the sand in the mix or can you just use 3.5 parts perlite (for more insulation, maybe)? If not, what is the purpose of the sand in the mix?

magicman391 13 years ago

what your essentially making is a kind of concrete that can withstand the temperatures of the furnace. when making concrete the basic ingredients are cement, aggregate (sand, gravel, or crushed stone), and water. Like i said in the refractory making step, adding more perlite can't hurt as its an insulator, but sand is neccessary in order to get the right chemical reaction for it to cure.

z.jordan 12 years ago

Technically, the curing reaction only takes place within the cement.

In other words, sand is not actually required for curring to occur. However, it is recommended because it helps increase the strength of the concrete as well as slightly reduces heat conduction.

ilikechemicals 13 years ago

Cool but step 7 pic makes it look like you didn't mix the refactory well enough.