Aluminum Melting

I’m actually working with Dave Hakkens, we would like to make our own aluminum models using a DIY rocket stove. So we could use these models to work with the injection machine.

Melting models by yourself is interesting for two main reasons : First because of the price. It is really expensive to get some CAD machines, or order these pieces from somewhere else whereas aluminum melting is a really cheap way to work, and it seems really easy.

In a second hand, we also would like to have a break with smooth industrial aspects. Making our own models with a rocket stove would allow us to create some textures, patterns, we couldn’t have with CAD process.

So this first post is about the rocket stove building :

I found many different ways to build a rocket stove, to melt aluminum it needs to go at least until 650°C.

These videos are good examples : ( Models 2 & 3 ) ( an easier and good model )

It is important to have a good isolation, to keep the heat inside, you can use :
refractory concrete
refractory concrete and bricks
a mix between 35% plaster, 35 % sand and 30% water
sand ( we tried, it was all right )

As container you can take a bucket, a gas bottle just be sure that it is in steel and thick enough.

We also put a tube at the bottom of the stove to feed the fire with an hairdryer, it’s really POWERFUL !

It took us around 15 minutes to melt 25 cL of aluminum.


There was a kind of waste on the aluminium, that is why some tutorials advice to melt the aluminium in two times. The first one to make pure aluminium ingots (small ingots will melt faster) and the second one, when you use your ingots for your real castings !

That would be an other topic, coming soon !

@xxxolivierxxx No i did not use borax for my project and yes i used a graphite crucible. The waste material aka slag floats on top of the molten aluminum inside the crucible. I would pick up the slag and separate it from the crucible. Once the slag is out of the crucible, only molten aluminum should be left inside, and ready to pour.

@traplocz That’s awesome
Did you have to add borax into the aluminum to remove the waste material? I’m looking forward to make one soon but haven’t decided if I should make it with sand and plaster or silica bricks.
Did you get a Graphite crucicle for yours as well?

Hello i am proud to say that i built a mini foundry. It took me 50 aluminum cans to make one pound. I poured my molten aluminum into a mini muffin steel pan. I am now looking what to do next.

Never tried, especially because it’s TOXIC !

I think that lead is too soft to do a mold with it, it might twists too easily ( when you try to take out your casting from the mold for instance :S ) i guess it depends the shape you want to make.

There are also silicones strong enough to cast aluminum and bronze into, didn’t try yet !

Lead has a melting temperature of 327,5°C. It is softer and easyer to work on. Also can be casted in silicone molds… Anybody tried this?

To reply to your questions #andyn , there is no discoloration with the polypropylene, in fact we put some yellow, orange and pink plastic in the same time expecting for funcky pattern…!

On the fird picture i put two température degre for each plastic, the first is the setting on the top of the injection tube, the second at the bottom, it has to be hoter.

Good to see the final step made it up here @tafnstuff! see you soon 😀

Thanks for posting the results! last photo, on the left, is the discolouration of the polypropylene due to the heat? What temperatures did you find work best for each type of plastic? Looks like around 255-260°C except for the ABS?

Howdy Ho !

Sorry of being so late ( i spent these last months without any single computer ).
This is the conclusion about the experimentation we did in October :

We finally managed to get our first aluminum handmade mold ! it looks exactly like the plaster one, from which we took the print. To easily connect it with the injection machine, we directly put a thread pitch into the sand so it got “stuck” in the aluminum. ( but after a few uses it came out … )
The special foundry sand allow us to keep almost all the details.

We also experienced that:

– you can use some polyester mastic ( Sinto ) to work on the aluminum, even at 200 °C, and after 10 casting, the mastic was Ok !

– you can put a bit of talcum powder inside your mold, it will be easier to take of your casting !

the last picture show you all the tries we did with different kind of plastic !

haven’t heard from @tafnstuff in a long time, whats up?

Yep, pretty cool stuff.
The name of that technique is “lost wax casting”

So have you seen how they bury styrofoam in sand with an extension to a sand funnel that they pour the aluminum into that displaces the styrofoam shape they made. Here’s the YouTube link

if this gives you any ideals that help!

@lyricalpolymath @davehakkens @tafnstuff I have nothing important to add here but id really like to take a moment and appreciate the fact as to where we all are going with this forum/website. It no longer is limited to those 4 machines and is also highlighting different methods, different projects, different ideas and different causes. All of which may help someone or other in making this place better than we found it. Every now and then someone like @lyricalpolymath posts a link which teaches me something totally new and truly appreciate that.

Thanks Precious Plastic,
Thanks Dave.

you guys rock! 🙂 We too had this planned.

here are a couple of interesting resources
I’m sure you are aware of Studio Swine’s Can City project

and some images of the products

Although it’s not related to aluminium casting, check out also the sea chair project 😉

This other project is awesome too: “Lost PLA Casting from 3D Prints”
which uses PLA 3D printed positive parts that are then employed like waxes in the thousands of years old “lost wax” technique (the heat of the metal sublimates the wax/PLA object

I have always wanted to have my own mini furnace to melt soda cans at home, but I don’t currently have enough room to safely build one.
Something I heard about bubbles in plaster molds, is that the only way to have a smooth mold is using a vibrator. That’s actually how dentists make your clay/plaster teeth molds, by pouring clay into a silicone/alginate mould and then placing it over a vibrator for a few minutes to remove bubbles, and the end result is perfectly smooth.

Min 14:36

@tafnstuff melting aluminum on our super professional set up. The hairdryer is crucial.

Our Aluminum mold made from our rocket stove :

first I made a kind of bowl in clay, with smooth surface inside, edges and textures outside

Next I made a plaster mold of this. This plaster mold is in two parts. For each part of the plaster mold I took a print with the foundry sand. So I made a sand mold for each part of the plaster mold : two sand molds for one plaster mold so.




Hello ! Here we are for some news about aluminium melting !

We kept making some tests with sand molds, we didn’t find some solutions for the plaster ( to many bubbles in the aluminum and impossible to get some smooth textures)

We bought some special foundry sand to compare with our DIY sand. The foundry sand is thinner than ours and it is also easier to keep it sticky ! We managed to get more details, even if you wait a day before casting into your mold, the sand is strong enough, it doesn’t get to dry. SO we decided to keep it to make our first aluminum mold for the injection machine !