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This is the first charcoal furnace that I built its purpose melting small amounts of aluminium into ingots or sand castings for small objects. I don't predict a long "shelf life" for my furnace before it will start cracking but I will get a few melts before I scrap it, This is just a prototype and hopefully in the future I will make a bigger and better furnace.
It's easy and quick to make, I will show in this instructable the steps on how to make it using materials some of us have in our house. The only "big" money might be the refractory materials and characoal.
A few details about my furnace: I made it all 2" thick around including the furnace lid. I used Plywood, MDF, cardboard, chipboard all left overs from other jobs.
The furnace tools I made from a 5mm construction rebar, can of beans and old bathrooms hooks.
In the near future I hope to add to this instructable a few images of my first sand casting.
A few Saftey words: Coming into contact with fire and boiling melted metal can be very dangerous so always work safe using proper full body protection including respirator mask against toxic fumes and dust from mixing refractory materials. Never melt in a wet area or near water, if water comes in contact with the boiling aluminium it might "blow" in your direction.
It's easy and quick to make, I will show in this instructable the steps on how to make it using materials some of us have in our house. The only "big" money might be the refractory materials and characoal.
A few details about my furnace: I made it all 2" thick around including the furnace lid. I used Plywood, MDF, cardboard, chipboard all left overs from other jobs.
The furnace tools I made from a 5mm construction rebar, can of beans and old bathrooms hooks.
In the near future I hope to add to this instructable a few images of my first sand casting.
A few Saftey words: Coming into contact with fire and boiling melted metal can be very dangerous so always work safe using proper full body protection including respirator mask against toxic fumes and dust from mixing refractory materials. Never melt in a wet area or near water, if water comes in contact with the boiling aluminium it might "blow" in your direction.
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Signing UpStep 1Furnace construction
A bit of form work: check if you have any scrap plywood, MDF etc' to hold the refractory furnace shape.
I used scraps of plywood, MDF, chipboard, soft wood, cardboard all screwed together.
Start with the walls and the base. Optional: making small wooden angles for the corners will make the corners flat preventing them from breaking.
Drill a hole 2" from the base using a core bit for timber. The diamater of the hole should fit the size of the pipe you will use for the blower.
I used a cardboard pipe to form the opening for the blow pipe.
I used scraps of plywood, MDF, chipboard, soft wood, cardboard all screwed together.
Start with the walls and the base. Optional: making small wooden angles for the corners will make the corners flat preventing them from breaking.
Drill a hole 2" from the base using a core bit for timber. The diamater of the hole should fit the size of the pipe you will use for the blower.
I used a cardboard pipe to form the opening for the blow pipe.
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i am sure i read somewhere that if the inner refactory mix is not to thick, and then surounded by a layer of sand (allows expansion) or probably ceramic wool, then a further layer of refactory insutation, then a expandable layer (you get the onion ring effect idea) then the refactory layers are allowed to expand and contract without too much stress and therefore cracking. i think some experimentation is needed.
to hold the solid layers together(at the top), some wire netting, or stainless steel wire in a zig zag fashion around the circumference (binding)between the layers would bind the whole lot together, whilst allowing expansion,
just food for thought
only one thing that could remove confusion: add something to the images to compare size, like a pet bottle or so. i thought this thing was tiny, but obviously it's not XD
After 2 or 3 hours from the pouring of the concrete, put a damp cloth over the top of the furnace. Keep it wet the whole time and protect it from wind, wich will dry the concrete. If the concrete dries it'll be a lot weaker.
Congrats for the great instructable.
I'd like to make you notice though, that you are not in the SAFE side!
You should operate on a bed of dry sand, not in proximity of a wood house
and on a not so dry soil.
If the melted metal drops to the soil it will instantaneously "explode" due to contact with moist/water on the soil and it would spray around spliters of melted metal.... mmmhh, I guess you dont want that!
I'm sure you have read suggestions and advices in
http://www.backyardmetalcasting.com/
Be careful.
Correct all above should be taken into consideration when working with molten metal.
Not that it matters but I work with full body protection so even if aluminium will "explode" no risk to me.
This specific MINI furnace I made Poses no danger to the wooden structure being caught on fire, I was working with charcoal (Easy to control) not waste oil (hard to control/on fire).
I have my water hose ready and no I won't water the molten metal.
Safety First ;-)
* I do think that chicken wire or small rebars will help against cracking, I didnt use it in my furnace and it cracked.
* I don't think concrete is the best insolator although I got very quick meltings using my furnace. The aluminium was melted in less then 20 mins.
* It cracks under high temperature but you will get a few meltings before the furnace will die.
*My next experiment is exactly what you are asking, I was thinking too that the tiles will take the heat but I have a feeling they will crack.
I will update my instructable if the experiment will work.
You can place the cement in some metal container, the container will probably prolong the furnace life. You can google furnace refractory mix and you will see many sites that provide guides for the proper materials and mix ratio.
Most people start by melting cans the only thing is you need a lot of cans to get some decent amount of molten aluminium. And the cans produce alot of slag that have to be removed.
I would recommend melting some aluminium objects that you have no use for they will give you more molten aluminium.