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Low budget aluminum casting

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ericc

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Over the weekend, I tried some ideas for economical casting of aluminum. It was mostly successful. I looked around for some guidance, but a lot of internet resources warned against using spent propane cylinders in solid fuel fires. Best to try it myself and see what the problem is. I'll try to attach some pictures.

Hmmm. It says the photos are too large and Amazon photos cannot resize them. I'll try to figure something out.
 

Latinrascalrg1

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Take a screen shot of the pic then post that, it should be a smaller file size.

Also not quite sure what you needed help with but i assume it was about using the propain cylinder as a crucible? If so the danger is cutting it open. In the past i have done so safety by removing the Schrader valve and filling with water before cutting. They work good for a few melts but will eventually burn through pending what temp you are running at.
 

Hawkeye

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Email the photos to yourself. You should get a dialog box that lets you select the pixels. I always use 600 x 800 for forum pictures. When they come in, save them in the same folder, but change the file name. I just add an 'a' to the end of the original name.
 

ericc

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Hey, it worked! Anyway, the pictures show the firebrick furnace, the fuel (hedge trimmings), and the crucible (disposable propane cylinder with flared lid). The steel did not burn up. It didn't even scale excessively. The trick is to go slow and don't blow too hard. In addition, put a long piece in, but make sure that there are a lot of easy to melt pieces in the bottom. Small is good.

There were two problems that I had. First, the cans were not on a level surface, so I had to turn off the wedge shaped top on my lathe. Second, the molds were soup cans, and they appeared to have a coating which gassed off, leading to inclusions. Next time, it looks like a custom made mold would work better.
 

RJSakowski

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Years ago, I used to do quite a bit of aluminum casting. I used a cast iron bean pot for my crucible. I made a propane furnace using firebrick and a homemade burner. I used a length of 1/2" black pipe for the gas supply with tees for three orifices. The orifices were made from brass pipe plugs drilled to the appropriate diameter. The fuel supply pipe was mounted inside a larger piece of pipe that fed air from a blower made from a variable speed automotive blower. The furnace could melt a 10 lb charge and could also melt copper and silver in it.

I cast my own lead fishing jigs and for that, I made a crucible from a four inch length of 4" black pipe. I welded a piece of 3/16" polate on the bottom and two washers for eyes for a handle. I use a small propane fired camp stove with a coffee can chimney for heat. I've used this setup for a quarter century now.

Back about forty years ago, I had some silver that I wanted to melt. I decided to use a small Corningware bowl for a crucible. It worked for melting the silver down but was fairly well toasted in the process. At the time, Corning had an unconditional guarantee against heat damage but somehow I didn't think that they would honor it for me.
 

ericc

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...
Back about forty years ago, I had some silver that I wanted to melt. I decided to use a small Corningware bowl for a crucible. It worked for melting the silver down but was fairly well toasted in the process. At the time, Corning had an unconditional guarantee against heat damage but somehow I didn't think that they would honor it for me.
:D Ha Ha. Seriously, it is pretty interesting that it worked. I was surprised that the disposable propane cylinder worked. I expected it to explode at once or at least to spring a leak like the youtube videos. Not even close. It looks great, and it looks like there's no problem doing a second melt with it. Still, I think that I'll throw it away and get a new one for the next round, but perhaps do two pours with one furnace charging. One of the main reasons that I am doing this is that the garbage service doesn't like us recycling these things unless we cut them in half. As long as you are cutting them in half, may as well put them to some use.
 

ericc

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I faced and turned one of the cast cylinders. It came out OK,except for the can grooves and the inclusions, possibly caused by the off gassing of the can inner coating. There must be a better way. When cutting apart these propane cylinders, there are leftover rings of steel that could possibly be repurposed into semi-permanent molds. Would it work to place one of these rings concentrically in a steel layer cake pan (no coating!) and fill the annulus with sand? Maybe, some retaining clips could be put in place to keep the ring from shifting. The aluminum would be kept in the inner circle by the sand around the bottom gap.

Do you think that this would work?
 

Latinrascalrg1

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Look into "lost foam sand casting" to easily make aluminum castings of just about any shape. Or if you need to make a copy of an existing part look into "greensand" or "oil bonded casting sand" because they are both highly compactable to hold very intricate and detailed mold copies and it reusable with a bit of work to resofen.
 

Latinrascalrg1

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Also forgot to mention coating the shaped foam part in a coating of plaster of paris slurry by dipping the piece and letting the layer dry a bit and then recoat until its got a nice shell. Then put that into a pile of regular sand into a hole in the ground and completely cover except the pour spout and vent stack but do not pack. This will give you a high detailed copy of the foam with a very nice surface finish compared to being very grainy effect you will usually get unless you use the finer mesh silica sand in the green sand form. Its the cheapest way to get the best surface right out of the mold if done right with every easy material access.
 

ericc

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Hi Latinrascalrg1. I'll try this out. Pour directly into the foam pour spout protruding above the surface of the sand?
 

Latinrascalrg1

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Pretty much but you need to put a can with both ends cut out around the spout to create the "funnel" to keep sand from collapsing into your pour. All but the top of the spout and vent spurs should be covered in plaster and the plaster needs to be completely dry or it causes big problems....mix it thin enough that you can either dip or "paint" on the multiple thin layers. i always do at least 5 coats +/- to account for slurry consistency which should be like thin pancake batter.
 
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Latinrascalrg1

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Check out this guys video, it gives a decently good description of the process and his voice keeps it a bit interesting.

Btw, i dont think sanding down the "thick" portion of the plaster is at all necessary as the reason for the Thinning is to make sure All aspects of the foam are coated in a way it can flow out so there are no bubbles or brush lines and to be sure it completely dries without cracking. Also the reason for the surface flaws and the ruff texture is because his plaster shell wasnt thick enough as you shouldn't be able to see through it.
Also if you wanted to go through the extra step you could burn out the foam core before you pour the metal which helps with the off gassing problem. Hope it helps.

 
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ericc

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I took a quick look at the video. There's a lot of work for not much gain (at least for casting gear blanks and flanges). The main defects may have been caused by excessive turbulence and pouring too hot. I had similar defects, probably due to the can coating off-gassing, but my result was actually a bit cleaner, despite the fact that very little time was used to prepare the can molds. Really, the only thing I did was place them over the furnace vent for a few minutes to make sure there was no moisture. Next time, I will do the experiment with an uncoated can, then go to the foam if really necessary. Actually, after turning the puck in my lathe, the only real problem was the ridges in the can that left "proving" marks on the surface. These go down about 0.1", so represent quite a bit of waste. The next can I use will have no ridges.
 

Cadillac

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If just making blanks of aluminum to machine down I use seamless pipe 3,4,6” big. Surface finish is good just have to wait for it to cool before it’ll slide out of pipe. I also use 4x4 and 6x6 square tubing to make square chunks.
 

savarin

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You can melt aluminium in tin cans, it works for one only casting as it will burn through on the second melt.
I've just cast two blanks this way.
scroll down to post 208
I've tried lost foam and plaster, a lot of work in my opinion for not a lot of gain.
I didnt like it but may have a go again in the future.
 

Hawkeye

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The crucible I use I made from a small fire extinguisher. Very similar in construction to a propane cylinder. It glows quite brightly, but is still solid. I've read that a bit of the iron does dissolve into the aluminum, but I promise not to cast any parts for a Mars lander.

Firebrick foundry, propane burner. You can see the crucible at the bottom corner of the picture.
PA240056a.jpg
 

savarin

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Heres the solid cast from the tin can. originally 98mm dia and 150mm long, reduced to to 85mm dia, the short end in the tailstock is 40mm long and 45mm dia.
No trace of porosity.
However, the centre wont be as good as there was no riser so there will be shrink cavities in the centre.
In this case it doesn't matter as the centre is being bored out.
The tail stock end is what was the base of the can and has set solid.
The top is really crap with some dross and a few shrinks but again I dont need that as the total length will be around 80mm long so I didnt bother skimming it before I let it set in the crucible can.
tin-can-cast.jpg

Some of the ingots that made up the total amount of aluminium (unknownium actually) did have a heap of visible porosity everywhere but by only just melting it seemed to remove them so I will do this on my next real casting.
I believe I have been getting the melt way too hot in the past.
 

ericc

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This is a great result from a tin can. Mine have porosity, but it is miniscule. There are hot tears and inclusions as well. I will turn it down more to see if it is clean. I only need two gears for now, the rest are flanges, which don't have to be very high quality.
 
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