FAIL: Home made aluminum ingot mold

[Revolver]

Well, my first attempt at casting my own ingot molds from aluminum failed... or maybe I should say it "almost worked." This was my first complex aluminum casting and my first using a pattern, I learned a lot and now feel I have the experience to succeed next time.

Basically I build a pattern from wood, then packed it in sand, then removed the pattern and poured aluminum in the cavity to make a metal replica of the original wooden pattern. I don't think I packed the sand tight enough (rough texture) and I had some thin parts of the pattern that crumbled (holes).

http://i1084.photobucket.com/albums/j407/mainejunker/83ff124a.jpg

[canyon-ghost]

My brick mold makes 5 pound ingots, made simply of 3" channel iron cut 6" long:

http://i758.photobucket.com/albums/xx228/3rdshooter/contenders/ingotmolds006.jpg

[Revolver]

That's cool, and I may resort to that, but lately I've become interested in casting aluminum.

[ReloaderFred]

I had my ingot molds made from 4" aluminum channel, cut into 8" lengths. The ends were welded and I get consistant 8 pound ingots from them, which are perfect for use in my Master Caster. The sides of the channel are sloped in the right direction and the ends were welded with the same angle as the sides. The ingots just drop out when turned over. The ends were made to stand about 1/4" above the sides to facilitate the ingots dropping out.

Hope this helps.

Fred

[jimkim]

Do exactly what you did the first time but cast it in wax instead. You can then sculpt the wax to the desired dimensions. Add a couple of wax sprues to the wax pattern you made. Place it in the form. Dust it with talc and sift green sand over it. Once it's covered good put unsifted green sand over that and pack it tight. Let the sand set. Once it sets up you can use heat to melt the wax. After that, pour the cavity with aluminum. I'm sorry I'm not the best at explaining the process. You can find videos on "lost wax process casting" on youtube.

[Mk42gunner]

Junker,

That doesn't look bad for a first try. Remember, you can reuse the aluminum that you have already cast.

It has been a lot of years since I cast anything from aluminum (in high school shop class); but I don't think you need to go to lost wax casting, although it might be easier.

Myself I just weld up some angle iron for ingot molds, but yours look like a good size.

Robert

[zuke]

If everything worked the first time we wouldn't learn anything.

[jimkim]

It's not about easier it's about improving the quality of the product. Just try it once. If it doesn't work for you, don't do it again.

[3006guns]

Roughness may be due to a coarse sand and the holes are from your sand collapsing. Fine casting sands are available from various suppliers on the internet and ordinary molasses mixed with water can be used as a good binder in a pinch.

Actually, I think your first attempt looks darn good! Just need to refine the technique and pretty soon you'll be offering them for sale to the members here.

Edit: I just remembered something from my high school shop days (when they actually taught you to use tools!). We made aluminum castings by first carving the item from dense styrofoam then tamping the mold sand around it. Risers and gates were formed with wooden dowels which were removed. The molten aluminum was poured in, vaporizing the styrofoam instantly and occupying its place. When the mold was broken apart you had an excellent casting.

Sort of a lost wax type of casting without the hassel of baking out the wax, but you had to make a new styrofoam piece for each mold. Might be worth considering though.

[WILCO]

lately I've become interested in casting aluminum.

Hey Junker,

Have you checked out Lindsay's technical books?:

http://www.lindsaybks.com/

I thought your ingot mold looked good for a first try.

[cajun shooter]

For a first try I would say that your work is not bad.
I had foundry shop for one year while attending school in Indiana and we used s dark colored sand that was very fine.

[Mk42gunner]

Roughness may be due to a coarse sand and the holes are from your sand collapsing. Fine casting sands are available from various suppliers on the internet and ordinary molasses mixed with water can be used as a good binder in a pinch.

Actually, I think your first attempt looks darn good! Just need to refine the technique and pretty soon you'll be offering them for sale to the members here.

Edit: I just remembered something from my high school shop days (when they actually taught you to use tools!). We made aluminum castings by first carving the item from dense styrofoam then tamping the mold sand around it. Risers and gates were formed with wooden dowels which were removed. The molten aluminum was poured in, vaporizing the styrofoam instantly and occupying its place. When the mold was broken apart you had an excellent casting.

Sort of a lost wax type of casting without the hassel of baking out the wax, but you had to make a new styrofoam piece for each mold. Might be worth considering though.

We only did a few items casting aluminum, but I remember a couple of guys forming styrofoam to make T handle shift knobs for their trucks, (think Hurst T handles). Like I said, we only did a few items, so I know just enough to be dangerous.


For a first try I would say that your work is not bad.
I had foundry shop for one year while attending school in Indiana and we used s dark colored sand that was very fine.

It seems like Fullers Earth was mixed with fine sand for the first layer around the mold. Does that sound right?

Robert

[Sonnypie]

Makes a muffin tin seem awfully inviting...
And my bread pans from the Goodwill Store.

[bumpo628]

Looks pretty good to me. I thought it was good when I welded my own ingot molds out of angle iron, but casting your own mold is way cooler. I would do it too if I had the means.

You could try grinding away any problem areas that prevent proper ingot release to save it.
Your ingots don't have to look smooth. This one could be used for a particular alloy so that you can tell them apart later. You can never have too many ingot molds...

Just keep at it and try again.

[Casting Timmy]

I used to work at a place that did some aluminum casting, oen trick to get a nice surface finish on the inside would be burying short sections of steel rod bar stock in your sand so that only the top third of the steel will be exposed. This will allow the aluminum to cool against the steel instead of sand and you will get a better surface finish.

Just preheat the steel to help the aluminum flow and don't think that the steel will just drop out when you're done. Most likely if the bar stock was cut square you'll have no draft so you have to wait for everything to cool and beat it out with a hammer.

Actually if you're not picky you don't even need a pattern, just bury the pieces of bar in your sand and make sure you have a cavity to fill with the aluminum.

Your casting looks fine, I don;t see any sinks in your cross members, but remember you can always add hydrogen to your aluminum by dipping a wet stick in it and stirring it around. The water will escape up the side of the stick and keep everything from blowing up, just remove the stick after you've burned a portion of it off in the aluminum. The incomplete burning of the wood will put lots of hydrogen in the aluminum and the casting will cool like a sponge on teh inside. There will be tons of porosity in it, but the outside dimensions will stay true.

[Daddyfixit]

Is that partical board on the bottom? At any rate I would sand the mould smooth and use a sealer on it, or use some bondo or? to fix up the alum one and use it as the new mould.

I to used to cast in High School shop, and I think we cast Hurst T-handles for everyone in the school! Thankfully Hurst never sued!

[Revolver]

Is that partical board on the bottom? At any rate I would sand the mould smooth and use a sealer on it, or use some bondo or?

The bottom is masonite... very smooth. I sanded the whole thing and polyurethaned it so it's super smooth.

It is built out of a wooden clementine box from the grocery store. (I like things that are free).

[Revolver]

...The incomplete burning of the wood will put lots of hydrogen in the aluminum and the casting will cool like a sponge on teh inside. There will be tons of porosity in it, but the outside dimensions will stay true.

Hi, thank you for this tip. Can you please explain to me the benefit of the hydrogen and porosity? This sounds very interesting.

Thanks.

[Reverend Recoil]

I use a cast iron corn bread mold to make lead ingots. It works well enough for me.

[Casting Timmy]

Hi, thank you for this tip. Can you please explain to me the benefit of the hydrogen and porosity? This sounds very interesting.

Thanks.

Aluminum will naturally contain hydrogen in the molten state, I think it takes twice as much nitrogen to get out the hydrogen from the mix.

If you can't add a riser to a part and need to eliminate a sink happening somewhere in your casting you can add the hydrogen back into the mix. Instead of the part being solid and shrinking or sinking in certain areas so can get the correct outside shape but put porosity on the inside of the part.

The disadvantage of adding the porosity will become vary apparent if you try and machine the part. You will expose all the porosity on the inside while machining and end up with a unslightly part. You will also end up with a weaker part than a solid casting, but in some applications you don;t need the full strength of the metal. It's more important to have something that looks right than being a solid hunk of metal.

Another way to fight the sinks is to poor your aluminum at a cooler temperature, that way it doesn't shrink as much or causes sinks. The trade off with pooring cooler is that it won;t flow as well and a raelly thin casting might not come out completely filled.

Our permanent molds would poor with 1400F aluminum. Sometimes scrap would be melted into a ladle when we had to poor the sand line so that the temperature would be brought down so we wouldn't get the sinks in the casting.

The coolest thing I saw in that foundry was a tea cup, sauser, and a spoon made as a single casting in aluminum. The guy that ran the foundry made it himself using a real tea cup, sauser, and spoon to make his mold pattern. That man really knew some tricks to get aluminum castings done right.

PM me if you have more questions, I don;t always check back with the posts and rarely subscribe to them.

[Revolver]

I use a cast iron corn bread mold to make lead ingots. It works well enough for me.

Yeah, I have one of those. It's kind of corny! :groner:

[acoop101]

Have you checked out the backyardmetalcasting.com forums? They have a bunch of hobbie metal casters that can give you tips and tricks that can help on small scale aluminum, bronze and in some of the more dedicated cases cast iron.