Activities on these pages about foundry work are very dangerous. The chances of having a fire, causing injuries, or even dying are very good if you are not careful. I am not a professional foundryman, and will not attempt to disclose all hazards. If you choose to try this hobby, every precaution must be taken to be safe. Remember, a hobby is only fun until you're standing in the middle of the street with your family watching your house burn.
In 1993 I was working in Lima, Ohio. A co-worker introduced me to a series of books about foundry work. My grandfather was a foundryman at a foundry in Dayton called GH&R. Perhaps this is why I became interested in this subject. Whatever the reason, I started to develop my own foundry.
A Little History
A fellow sheet metal worker from Missouri named Dave Gingery developed a method for building equipment from scrap aluminum. His equipment can all be built with the furnace he developed, which holds a crucible that holds a few pounds of aluminum. The fuel for melting the aluminum is provided from regular, store-bought charcoal.
Dave's books are available from Lindsay Publications . Lindsay has books on just about anything you could be interested in, from making your own soda to building a radio from scratch. Some books are reprints of books written as early as the nineteenth century, but others have been written recently. Their website has a listing of the books they offer (I'm not sure how complete it is, but other links might take you to all). One feature that I have just found out about is an archive of technical articles.
. . . And on to My Shop
Here you can see my furnace. It consists of a metal five-gallon bucket with a two inch thick refractory layer. Toward the bottom is the tuyere (pronounced 'tweer'), through which the air blast is delivered. This setup has a 12-V blower, but it did not have enough power to successfully melt the material. So I added a PVC wye and put a hair dryer on top to correct the problem. After a while the blower motor started to act up, so I replaced it with a 120-V AC motor. A lid filled with refractory mix (not shown) is set on top. The lid has a hole to let the air out, and material can be added until the crucible is full.
Before melting the aluminum a mold must be made. This mold has cavities for a table for the horizontal mill (in the back), a step pulley (left), and an upright for a dividing head. In the top can be seen the sprues through which the aluminum is poured (the three larger holes) and the legs on the upright. When the mold is closed, the holes line up with the cavities. The white dust on the surfaces of the mold is parting dust. Parting dust will not absorb water, so it separates the halves of the mold, allowing the mold to be opened and the patterns to be removed after molding.
This is the mold after it is closed and ready to pour. Kind of anticlimatic, isn't it?
Here I am pouring the molten aluminum into a mold. I normally make two molds at a time so I don't have to set up the furnace as often. Since it uses charcoal it must be done outside, unless you don't mind carbon monoxide poisoning. The metal must be superheated to about 1200ºF in order to pour properly. As the aluminum goes into the mold it acts like water, except that the sand will not absorb it. Also, the metal in the sprue pushes down on the metal in the cavity, helping to fill it.
During the remodeling of my workshop my furnace got knocked around a bit, and the top of the refractory broke out. I am planning on converting over to propane soon, but I wanted to start casting parts. So I took some commercial refractory mix and relined the furnace. In this picture I am firing the lining. The vent hole in the lid shows the flame from the charcoal, and a carbon build-up on the right.
These last two pictures show something important. In the first I am pouring over a bed of sand. This is very important, since any spills will be contained. The sand will not melt since its melting pount is over 4000ºF. But at the time of this picture I had little room in the garage. So what I had to do was to make a small cart with wheels to hold the sand, but the furnace was on an asphalt driveway. This means that I had to carry the crucible, nearly full of molten aluminum, over a short part of the concrete garage floor. This is a big no-no. In my new workshop I have enough room so that the furnace and molds are all over the bed of sand.