In my first post I wanted to share with you the process to make some coins in aluminum recycling cans with petrobond-type sand molds. To make the original I use a 40w CO2 laser machine, with it I engrave and cut the figures in methacrylate. (plastic works very well because it comes off very easily from the sand mold and gives very good definition) better than with wood. Once the originals are made with a box with keys and sand like petrobond or greensand I make the mold (I apply talcum powder to the piece so that it does not cost to get out) but being plastic the truth is very easy. In the mold I make a hole for the pouring in the back of the coin, around the center, and holes in the smaller sides so that the air can escape. These holes are joined making a small groove with a cutter. I leave you a video if you are interested in the process! Do you think I can improve something in the process? Do you have any ideas to apply?
Welcome Javier, To use an American expression, your coins kick ass. A few suggestions. Screen your sand through a sifter or mesh on the surface of your patterns so theres no lumps (facing sand). Once the pattern is covered, then fill your flask up with unsifted sand. That will improve your chances of getting a perfect finish. Try to find better metal for casting. Something that was previously cast like tire rims or automotive parts are much better alloy than cans for casting because it flows better. Just beware of magnesium in some auto parts. The non-stick coating on your baking pan may be toxic. Teflon coatings maybe outlawed in Spain, I dont know, but the smoke from it is poisonous. Thanks for posting the video! Pete
You're getting great results! And I have a few suggestions as well. Rather than prying out your patterns with a knife you might try taping them gently with a wooden handle. This will loosen them in the sand. Then you can lift the entire flask and sqing it upside down and let the patterns fall out by gravity. Do you have a taper on the edge of the patterns to help them come out of the sand? Rather than the time consuming action of cutting the cans up have you tried pounding them flat then bending them with a hammer? You may find you can get more aluminum into the crucible by compressing them. A larger basin cut into the sand to pour into will help avoid spilling hot metal. For safety from fumes from burning ink on the cans it is best to work outdoors. Keep up the good work!
Tank's for your answers and information! For the advise of toxic fumes normally I do outsides but for filming the video I have no light and I think it will be good to do inside (I was bad) Normally I do it with recicled cast aluminium but I want to share that you can make it with cans. I don't know if my coins kick ass, it's a good or bad thing ( I'm from Spain) sorry for my English
@oldironfarmer I don't have a taper on the edge but it takes out easy I think because talcum powder. If I don't put a sheet of wood under when I turn the box with sand, coins come off. I tried to smash the cans but the crucible is very very small on diameter. It's really time consuming but normally I do it with larger pieces of cast aluminium. I did it to show how you can recicle.
Kicking ass is a good thing. They do look great! Maybe you could make 2 sided coins by using a runner and gating system that fills them from the edge instead of having your sprue go directly into them from above. In theory the bottom side of the coins could also end up looking even better than they already do. But being so thin, they might be hard to fill that way using the beverage can metal. Cast aluminum might have a better chance, as mentioned above. That's if you wanted to make them 2 sided. Otherwise, if something isn't broken... don't try to fix it! Jeff
@Tobho Mott I tried to fill to the edge but as you say it was too thin that never fills good. I will be trying things that's what I like! I will share new things! Thanks for your answers!!!
Javier, do you have access to a small lathe—-wood turning or metal turning? If so, as suggested above, you could side gate your molds and then, using a faceplate, turn the edge of your coin to remove traces of the side gates. Side gating would allow you to have both the obverse and reverse sides of the coin include attractive relief. Making a setup to turn the edge of the coin is pretty easy. Your coins are really nice—-they “kick ass” as previously observed. ;-) Welcome to the forum. Denis
Your coins are stunning. What sort of losses do you get with your cans? I'm finding that I lose maybe as much as 50% of the mass of the can. I do get quite a bit of slag. Your pour was super clean and you had relatively little slag. I've a feeling there's a lot of paint and lacquer on the cans which burns off. I also suspect that I'm not melting them quickly enough and the ally is oxidising.
2 things that will minimize your oxidation are: 1) reducing the exposed surface area by crushing the cans as tightly as possible (cutting up and stacking is pretty ambitious) 2) submerge your additions completely under the molten pool so they are out of the atmosphere. The second point is where you can get into trouble with entrapped moisture. It's a serious hazard and needs to be avoided. Option: got a woodcutting bandsaw with a course blade? Saw the tops off the cans and throw the rest out. Pete
This completely computes. I've already made my first mistake in that most of my cans are crushed to save space, so removing moisture can't be achieved that way. I suppose I could cook the cans at a reduced temperature to vaporise. I do have a couple blades for the bandsaw. I normally consider the course one for wood and the fine one for metal. Cans are sufficiently thin that I would (in future) definitely use the wood blade to fast-rip them. Thanks. Either way, it sounds like I should start with a good pool, by re-melting a couple of sacrificial ingots, and bung the cans in fast. I suspected that's where I was going wrong.
