The Coffee Can Foundry

My fun, simple, and best of all, CHEAP introduction to aluminum casting.

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Introduction

During the summer of '98, in the newsgroup rec.crafts.metalworking, I saw mention of the miniature foundry project detailed at http://web.wt.net/~hmsc/may97/may97.htm (Unfortunately this page appears to have disappeared)

Shortly thereafter (about 7 seconds after reading the web page) I started thinking about potential improvements/modifications.

Over the weekend of Oct 3&4, 1998 I had the opportunity to put my ideas to the test. This is my report on the results.

Procedure

• My first modification was to use 1 1/2 lb coffee cans instead of 3 lb cans because that is what I had on hand.
• The second modification was to use a second coffee can, rather than bricks, to support the "firebox" and to form a plenum which more positively directs the air flow up through the fire. (Left picture, below) The top edge of the can has vertical slits about 1.5" long space about 1" apart, all the way around. This allows the top to flare slightly.
• The third modification was to use a can opener (the kind that punches a triangular hole in the top of the can) to punch a row of holes around the edge of the bottom of the "firebox", for air holes. I also used a phillips screwdriver to punch a number of holes in the center area of the bottom of the "firebox" (Right picture, below. Bottom view)
• The final modification was that instead of using a shop vac or hair dryer as the blower, I used a small 12v powered blower which was designed for inflating pool toys and air mattresses and suchlike. That is the orange thing in the left picture below. Again I used this because it was what I had on hand. It also offered me the advantage of being free from mains power. There is a steel pipe connecting the blower to the plenum. I wanted to keep the PLASTIC blower as far from the fire as I could manage.

Shortly after lighting the fire.

The first melt nearly complete.

The setup worked quite well. I did have to splice in an extention to the power cord of the blower, however, to avoid having to run the foundry IN the passenger seat of my truck. I was concerned that this small blower would not provide adequate airflow, but this fear was unfounded. It performed flawlessly. Perhaps the use of 3lb coffee cans would necessatate the use of a more powerful blower because of the greater amount of fuel.

Results

For the first melt, on saturday, the furnace performed above my expectation, but the resulting metal proved mediocre.

The problem was that the wall of the crucible burned through in several places causing me to spill some of my melt. After everything cooled, the can had almost no physical integrity left. I was able to crumble it with my bare hands. I melted a total of 16 aluminum beverage cans, and allowed all of the dross to build up as I added cans to the crucible during the melt. I believe this contributed to the mediocre result. It seemed that a lot of metal stuck to the chunks of dross. I also believe that the metal was too cold when I poured it, judging from the texture of the surface.

The second melt, on sunday, worked MUCH better after some thought and an equipment upgrade. I went shopping Sunday morning in search of a stronger crucible. I settled on a set of 4 stainless steel measuring cups from Mega-Lo... er, Wal-Mart for about $4.00 american. The 1 C measure was almost the perfect size. The diameter was right, I would have preferred it be a little taller, however. (The other 3 cups in the set were quite happily recieved by my sister-in-law, for her kitchen)

This time, I melted 12 cans, and skimmed the dross 3 or 4 times during the melt, as I added cans. The crucible stood up to the heat quite well and I managed about 75% yield, by weight, (about 30 to 50% by volume) of useful metal.

Conclusion

The SS crucible looks like it would easily withstand many more melts without self destructing. The coffee can used for the firebox stood up much better than I expected. Other than the paint burning off, and some surface oxidation, it doesn't look like it degraded much at all. This was a fun, simple, and cheap introduction to aluminum casting. My only expense was the $4.00 for the SS cup. All of the other materials were already at hand.

I am looking forward to trying this again. It will likely have to wait till next spring, however, as winter is rapidly approaching and my wife is expected to give birth to our first child any hour now.

UPDATE 4/16/99

My wife did indeed give birth shortly after I published this page.
Go back to our main page and follow the link to Justin's page.

I am still planning to do more melting this summer. Warm weather is rapidly approaching and I have begun collecting materials for my CCF Mark II.