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 Post subject: Aluminum Foundry Mk III
PostPosted: Thu Aug 18, 2011 10:28 pm 
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Location: Coon Rapids
So, the last 2 wednesdays at the Hack Factory I've been working on the Aluminum Foundry Mk III. (Sorry about the toxic smoke the other week, folks. ) I call it the Mk III because it's the 3rd aluminum foundry I've built, each one getting progressively larger.

The Mk I version dates to about 13 years ago: http://www.visi.com/~darus/foundry/

The Mk II version dates to a few years after that: http://www.visi.com/~darus/foundry2/
This one still lurks in the dark recesses of the Hack Factory.

The Mk III is using a 5 gallon metal bucket as the outer shell.
My goal is to try my hand at some green sand casting and some lost foam.
I know there are several other Hack Factory denizens who share a common interest in molten metal.

In the interest of furthering our common goals I'm putting the call out for assistance.

What we have:
1) The beginnings of the Mk III foundry
2) A steel crucible
3) the beginnings of a batch of green sand.

What we need:
1) Flasks for holding green sand molds
2) Lifting tongs and pouring shank for handling the hot crucible full of molten aluminum
3) We need aluminum to melt. The ideal source is things that were cast from aluminum in the first place. Aluminum engine or machine parts, casings, etc... Second, any unpainted, uncoated aluminum. Last choice, painted, anodized, or otherwise coated aluminum, including beverage cans.


The plan:
1) I can finish the construction of the foundry itself. I need a cardboard tube (sonotube?) about 8" OD x 12" or more tall for a form for the inside diameter of the foundry. I'm thinking cardboard because then we can just burn it out rather than having to worry about trying to remove it. My second choice would be a sheet metal tube (stove pipe?) that could be split down one side.

2) Someone with wood working skills can build a flask or two.

3) Someone with welding/smithing ability can create the lifting tongs and pouring shank. Also probably need to weld some ears on the crucible for positive gripping. We don't want a crucible of molten aluminum to get loose on us.

4) Riley finish the green sand mix. What do you need in order to finish?

Comments?
Suggestions?
Bueller??


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 Post subject: Re: Aluminum Foundry Mk III
PostPosted: Fri Aug 19, 2011 12:07 am 
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How about an old aluminum extension ladder? I retired it a couple years ago because the rungs were coming loose - and cut it into short pieces (I had a neighbor who liked to help himself to it - even after I told him it was no longer safe to use...wanted to keep from getting sued.)

I was about it take it and sell it for scrap - but if you can use it to melt - I'll bring it in.


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 Post subject: Aluminum Foundry Mk III
PostPosted: Fri Aug 19, 2011 6:35 am 
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Joined: Thu May 12, 2011 3:46 pm
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Location: South Minneapolis
What are the specs on the flask? How big, what shape, etc. Sounds like a lathe project. And what kinda wood?


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 Post subject: Re: Aluminum Foundry Mk III
PostPosted: Fri Aug 19, 2011 12:15 pm 
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Location: downtown Saint Paul
I am so glad that you're doing this.

re: 1. furnace construction. I have a piece of metal that should be exactly the right size, I pulled it out of a dumpster and set it aside specifically for this use. I'm stopping by the space very briefly today to pick up some clutter, and will put this in my pile I showed you for potential metal casting kit parts.

re: 2. flasks
I have Detailed Plans for flasks from the Dave Ginger book on building an aluminum foundry furnace. I will bring in these plans, and start construction of the flasks. The drawer sides we have will work perfectly for this. Chris, I'll bring you up to speed on what these look like, function, form, and purpose, and you can unleash your woodworking magic. Casting flasks are basically a matched pair of wooden boxes that stack on top of eachother and fit together tightly; there's usually a hinge on one corner and a hasp on the other so you can unlock them after and knock the sand off of the finished casting. Although they're called flasks, they're not flasky in any usual sense, and won't need a lathe. Wooden patterns, tho, especially the stepped pulleys and floating arm trebuchet bearings I want to make, do make good use of a lathe.

Here's a wiki article on flasks: http://en.wikipedia.org/wiki/Flask_(casting)

Here's the super duper wicked cool ZOMG we need to make these aluminum flasks: http://www.backyardmetalcasting.com/alumflasks01.html

re: 3. Thank god there are welders, I'm not one, and this is a hardware issue, so there you go.

re: 4. green sand for casting.

I have a crappy ball mill that I"m going to be refurbishing for this project. It was the first thing I worked on at the space, and it looks it. It's going to be made better faster stronger harder. I think I have all the parts I need for this, the one exception will be a large quantity of ball bearings. These can be purchased at axman, hopefully using the 10% off coupons we have; I need to find out exactly what size before we buy them, and hopefully someone who's not me can purchase them, as I am bwoke.

The ball mill will be used to pulverize kitty litter into bentonite clay powder, which is one component of the cheap green sand recipe; the other parts are water, and fine silica sand, of which I have a lot in a bucket at the space. The water should not be hard to find.

The ball mill will be good for initially "reconditioning" the green sand; down the road, we'll want to make a "muller", which looks like an industrial food procelssoer.

Again, I have Detailed Plans for this. once we start casting, it will be easier to make.

Once we get up and running, there are open source plans out there for the next level of better green sand recipes; I'll dig up a recipe for that when the time comes.

An aluminum ladder should provide excellent stock for casting, please bring it in.

One last thing;

The "Lost foam" method excites me much, as it's a really good fit for what we already have at the space.

Basically, you make a positive shape of what you want to cast out of pink construction foam. You know, the stuff that Pete's cnc machine cuts so well.

Then, you take that, and coat in what I think is drywall mud; basically thin runny plaster.

You let the postive dry for a couple days, glue on some square in cross section pink foam "sprues", submerge the coated positive in regular sand, leaving the sprues sticking up. Then, you put a coffee can on top of the sand, surround the sprues. You poor the molten aluminum into this. The can lets you build up "head pressure", and forces it's way down through the foam, burning the foam, and filling the resulting void with tasty tasty aluminum. Let it cool, empty the bucket, and you have your super duper metal piece, without worrying about casks, green sand, 3 part molds, or draft in your wooden patterns (that you're not using.)

Here's my favorite lost foam casting tutorial(got it via MAKE magazine, yay!) , it covers making exactly the kind of bearings I want to make for my floating arm trebuchets, as well as for when I ever get around to starting my cnc project: http://www.buildyouridea.com/foundry/lost_foam_howto/lost_foam_howto.html

That's my book length post for the day, if anyone has questions or comments, let me know. I'm really stoked about this, Jim, I'm glad you're pushing it forward.

Riley

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 Post subject: Re: Aluminum Foundry Mk III
PostPosted: Fri Aug 19, 2011 3:38 pm 
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I'd like very much to be involved, and would be happy to carve whatever for lost foam casting or molds for regular casting, I know just a bit about it, a guy on one of my CNC forums built his CNC pretty much exclusively to build molds for AL casting.
(he uses the oil / bentonite ? clay and old car parts as raw material engine blocks and rims and such.)

I don't have a lot of time at the moment, but if you get me files of what needs cutting I'll find a way to get it done. My 1st priority is clean up though, since I missed the last.

Pete


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 Post subject: Re: Aluminum Foundry Mk III
PostPosted: Fri Aug 19, 2011 3:46 pm 
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don't use kitty litter when you can buy bentonite. i bought some from from minnesota clay in edina right off washington. (http://www.minnesotaclayusa.com/). the stuff i bought was super fine.

it'd be better to get real green sand but i'm cheap.

http://www.tcmaker.org/blog/2009/10/dis ... um-casting


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 Post subject: Re: Aluminum Foundry Mk III
PostPosted: Fri Aug 19, 2011 5:02 pm 
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It seems hard to argue with $8.50 for 25 lbs, good call Bobble.

Also, Minnesota Clay stocks Skutt parts too, which is nice as we need a few for the kiln. Though I think I'd pass on the $150 ring of stainless steel they are offering for the top and just go to discount steel for that.

Pete


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 Post subject: Re: Aluminum Foundry Mk III
PostPosted: Fri Aug 19, 2011 7:18 pm 
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Location: downtown Saint Paul
8.50 for 25 pounds is less than what I'm paying for kitty litter... wtf!

I need me some of that clay. Badly.

Riley

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 Post subject: Aluminum Foundry Mk III
PostPosted: Fri Aug 19, 2011 8:02 pm 
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Joined: Thu May 12, 2011 3:46 pm
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Location: South Minneapolis
Thanks Riley. I just used the google machine to find some examples. My only question now would be: how big does it need to be? I'd be eager to help out.


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 Post subject: Re: Aluminum Foundry Mk III
PostPosted: Sat Aug 20, 2011 8:12 am 
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Joined: Sun Jul 26, 2009 4:27 pm
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curious... what items are going to be cast?


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