METAL CASTING: Backyard metal foundry, introduction

Time to start a new project, which involves extreme temperatures, molten metal, sublimating foam and more like this. 

My propane burner


Backyard metal foundry will enable me to melt metal scrap into useful drafted objects that could be later machined with precision.
Temperature achievable at home (up to 1200°C) enable to melt aluminium, brass, copper, bronze. Iron requires higher temperature and different techniques.

The receipt involves few elements:
- a liquid propane tank. Liquid Propane has various advantages in respect to traditional charcoal foundry: requires less space, because energy density is higher, so mre energy. Here you could find in local stores 30 liters propane tanks with standard attachment.
source Own Work - author Hustvedt

- a propane burner
. There are various models you can build, with back air or with venturi effect. The one i decided to build is the simplest one. It attaches to propane tank with standard pressure reducer, then with a pipe attaches to a custom burner based on two elements, the burner itself which is a drilled steel water pipe of standard length and the gas diffuser, another steel pipe with tiny hole on the center. The gas flows from the tiny hole then mix with back air and blows a blue flame of high temperature. A possible add-on may be a back air blower to enhance the oxygen available to complete the combustion inside the foundry.

Note the burner itself has specific dimensions and more air holes to capture oxygen.



- a foundry. This is where the burned gas inside a refractory lining fuse the scrape metal. The construction of the foundry is more or less a metal barrel with refractory cement on the bottom and on the walls. A removable cement top hat with hole, to regulate the heat into the chamber, complete the foundry.
For my application i found a convenient olive oil barrel that I cutted with grinder. On the side, near the bottom, I will drill an hole with specific angle to introduce the burner.


- the crucible. for hobby metal needs simple steel barrel is sufficient. For more specific application sintered crucibles made from ceramic or oxide powder is required because molten metal (Specifically aluminium react with iron). And more could be easily replaced.


- a flask with sand and cavity or, in my case, foam. Foam metal casting is a recent technique in which a foam pattern remain inside the sand. The molten metal replaces instantaneous the foam sublimating it. After cooling the foam is no more present and the metal has the design of the foam pattern.
Find more information on this process on wikipedia.
Of course the best site around from 2000: http://www.backyardmetalcasting.com/

- the pattern, that could be easily machined with cnc or standard technology.


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