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CFLBob

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There's a handful of videos on YouTube about chocolate printers, but I don't see any printing sugar like that.

Other than the high coefficient of neatness, I can't see why I'd want to do it... but I want to do it.
 

awake

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There's a handful of videos on YouTube about chocolate printers, but I don't see any printing sugar like that.

Other than the high coefficient of neatness, I can't see why I'd want to do it... but I want to do it.
Me too! I can't think of any good reason I need it, but I still want to do it.
 

awake

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Very interesting indeed! I agree, Bob, that it is likely extremely expensive. But ... it might be possible for a hobbyist to make such a machine ... surely no harder than making an 18 cylinder radial. (In other words, easy-peasy, right?? :))

Here's how I'm guessing it works (similar to how some laser-sintering metal printing works): The build volume is a tub with a movable bottom. The bottom is positioned to allow just enough room for one layer of sand, and sand is spread over the tub. Resin - maybe UV activated? - is essentially ink-jet-printed on the layer, binding the desired bits of sand to each other and to the previous layer. The bottom moves down a tiny amount, making room for the next layer, and then the process repeats.

One advantage of this approach is that parts can be printed "in space," since all of the sand is left in the tub, whether bonded or not, so it can support parts and features without concern for overhang.

There would be some tricky issues to resolve - how to move the bottom of the tub down without binding up with grains of loose sand, how to get an even layer of sand spread, how to make sure enough resin is used to bond to the previous layer without either spreading out and causing artifacts, or building up too much to allow gas to release through the sand ... challenging engineering problems, but clearly doable, since they've done it!

Mind you, I don't have any plans to take on a project of this scope. I'm still trying to find time to get back out to the garage to finish my half-finished Tower engine. I'm just hoping one of you is inspired to give it a go ... :)
 

stragenmitsuko

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Just imagine having such a , even a tiny one , machine at home .
No more moulding , no more pattern draft , forget about core making , no more gates and feeders and risers ....
oh wel , keep on dreaming .... and I'm already very happy with the 3d printed patterns anyway .
 

Barnbikes

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Okay, now I REALLY WANT to make a coffee mug out of sugar! :)

Sounds like a over sized complicated cotton candy machine in the making here.
Honestly I do not think it would be that hard. Pressurized pot set at the right temperature with a tiny nozzle. Replace the Dremel on your homemade cnc machine with the pot.
 

GreenTwin

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I stumbled across this thread today, and somehow I missed it entirely when it was posted; perhaps it got posted before I joined here (edit: checking my join date, indeed that is the case).
Not sure how I found it exactly, LOL.
I was searching for something, and there it was (ain't old age great? you don't know where you were going, or how you got there, but you like what you see when you get there).

I got the backyard casting bug in 2011, and started playing around with burners and simple furnaces made from stacked bricks.
I used a welded steel pipe for a crucible.
I melted aluminum for a while, and then saw someone online who successfully melted iron with an oil burner, so the quest for iron was "ON"!.

Six years later (on and off trials as work allowed), I finally mastered melting and pouring gray iron.
I learned a lot about pouring aluminum along the way.
I cast the engine in my avatar in 356 aluminum and gray iron (flywheel in gray iron).

There has been some debate about the techniques for degassing aluminum, with some using washing soda, and some using pool shock (toxic fumes).

I tried the washing soda, but I found that the gassing that it does when plunged into molten aluminum is caused by it absorbing moisture, not by the aluminum releasing hydrogen or any other gas. If you dry the washing soda an oven, you will get no gassing after plunging it.

The best way I have found to avoid gassing in aluminum is to bring it quickly up to pour temperature (I think I have been pouring at 1350 F), and then immediately pour. If you overheat aluminum, or let it sit for any period of time after it reaches pour temperature, it will absorb all sorts of gas.
I have had good results using this method, and have not had to resort to using pool shock or any other additive.

There is a bit of an art to casting things, and for long thin pieces, I have found a knife gate to be very effective.
I knife gate runs down one (sometimes both) sides of the mold cavity, and is connected to the runner.

Nice work in the flywheel.

Edit:
I use an oil burner with a siphon spray nozzle, and a leaf blower for combustion air, to melt gray iron.
I use a Morgan Salamander Super clay graphite crucible with iron, and use a separate one of the same type also for aluminum.
The crucibles can be purchased in many sizes on ebay.

The trick with melting iron is to use about 2.7 gallons/hour of diesel (some use waste oil, I do not), and adjust the variable speed leaf blower to get about 3" of flame out the lid opening.
The furnace needs a good refractory with iron melts, and I use a castable refractory called Mizzou.
Some use ceramic blanket coated with I think bentonite, and that will work for a while, but probably not as long-life as Mizzou.
Mizzou is rated I think at 2,900 F.

Edit2:
Not to highjack this thread, but here is a link to my videos that I think works:
Lots of trial and tribulation in these videos. I tried many many things before I got a good working format to pour iron successfully.
I used the spoof screen name "Raphael Mantegna" to try and throw the telmarketers and other sales shammers off the track (I am Pat J).


.
 
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solarenergyadventures

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I've been casting aluminum, and some iron, in my backyard for years, and in my experience, degassing is rarely necessary. The main gas that aluminum absorbs is hydrogen which comes from incomplete combustion of your fuel. The trick is to fire slightly fuel lean. In order to do that, you fire up your furnace, turn up the fuel and air until the furnace is making maximum noise, then turn down the fuel until the roar just decreases slightly. Now you are burning slightly lean, so there is slightly to much air for the fuel. Under these conditions, there is very little free hydrogen for the aluminum to absorb. Also, do not disturb the dross on the surface of the molten aluminum until you are ready to pour, as it helps shield the aluminum from the combustion gasses. Another option is to use charcoal or coke as your fuel because they don't contain any hydrogen in the first place. If you really feel you have to degas, use a lance to bubble dry nitrogen or argon through the molten aluminum. This works well with no nasty fumes! 😁
 

SmithDoor

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Here is information on green sand that maybe in your backyard.

Green sand: Green sand is also known as tempered or natural sand which is a just prepared mixture. of silica sand with 18 to 30 percent clay, having moisture content from 6 to 8%. The clay and water. furnish the bond for green sand. …
 

L98fiero

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I stumbled across this thread today, and somehow I missed it entirely when it was posted; perhaps it got posted before I joined here (edit: checking my join date, indeed that is the case).
Not sure how I found it exactly, LOL.
I was searching for something, and there it was (ain't old age great? you don't know where you were going, or how you got there, but you like what you see when you get there).

I got the backyard casting bug in 2011, and started playing around with burners and simple furnaces made from stacked bricks.
I used a welded steel pipe for a crucible.
I melted aluminum for a while, and then saw someone online who successfully melted iron with an oil burner, so the quest for iron was "ON"!.
This is a bit old but I have a question for the experienced casting members.

I did a bit of sand casting aluminum about 30 years ago, just a crucible, some firebricks and a propane weed burner torch for the melt, it actually worked out ok, first time!

Anyway, I'm looking at trying again and was looking for a better furnace arrangement and someone suggested the Devil Forge furnaces, one has only a ceramic blanket and refractory on the inside, the other has a refractory surface, is the ceramic blanket going to be a reasonably long term solution or would it be better to spend more time/money for a better furnace? What kind of life could be expected from the ceramic blanket model?
 

GreenTwin

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The ceramic-blanket-lined furnaces will hold up ok, but you need to spray the furnace/blanket interior with a ceramic-based coating (I think the coating that is often used is satanite). Some furnaces come pre-coated.

If you don't plan on melting iron, a coated ceramic furance will last a while (such as with aluminum).
I do know someone who melts iron with a satanite-coated furnace, so it can acually be done.

I prefer cast refratory, such as Mizzou, but I do a lot of iron work.

If you damage the ceramic blanket, just spray on some more satanite.
And you can replace the ceramic blanket completely at a reasonable cost, and re-coat it (using a good dust mask; don't inhale ceramic blanket fibers, and thus the coating).

And the ceramic blanket furnace is lighter.

Another option is to build your own furnace, if you are so inclined, as many/most backyard casters do.
You would need a welder and some metal working equipment to build your own.

.
 

L98fiero

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The ceramic-blanket-lined furnaces will hold up ok, but you need to spray the furnace/blanket interior with a ceramic-based coating (I think the coating that is often used is satanite). Some furnaces come pre-coated.

If you don't plan on melting iron, a coated ceramic furance will last a while (such as with aluminum).
I do know someone who melts iron with a satanite-coated furnace, so it can acually be done.

I prefer cast refratory, such as Mizzou, but I do a lot of iron work.

If you damage the ceramic blanket, just spray on some more satanite.
And you can replace the ceramic blanket completely at a reasonable cost, and re-coat it (using a good dust mask; don't inhale ceramic blanket fibers, and thus the coating).

And the ceramic blanket furnace is lighter.

Another option is to build your own furnace, if you are so inclined, as many/most backyard casters do.
You would need a welder and some metal working equipment to build your own.

.
Thanks for the reply.
When I was doing the casting the 'best' burners were the ones Ron Riel designed, has there been improvements and are there better designs, I have full machining and welding capabilities so building is not a problem, I think I just need more information of best practices or designs, recognizing the best is pretty subjective, I can't see that I'll be casting more than aluminum.
 

GreenTwin

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Ron Riel has a good propane design.
For propane, you may need a flare on the end of the burner tube to keep it stable while things are heating up.

Once the furnace is hot, you don't need a flare, and some don't use them with propane burners used with a furnace.
For a forge, you do need a flare on the burner tube.

You can have a naturally aspirated propane burner, or a forced air burner.
The forced-air propane burners get very hot, and will melt iron.
For aluminum melts, I use a naturally aspirated propane burner.

If you don't control the air choke closely on a propane burner, the mix will be too lean or rich, and you can either get a flame-out, or use a lot of fuel while still having a cooler furnace.

I have seen a Riel design with a choke added to the back of the burner, and this is the one I would recommend.

The trick with a furnace is to combust all of the fuel that you put into it, which means getting the exact ratio of fuel/air, either by natural aspiration, or with a small blower for combustion air.

If you want a faster aluminum melt, use a combustion air blower.
I have brought 20 lbs of aluminum to pour temperature in 12 minutes with an oil burner.
Be sure not to overheat aluminum. Pour immediately at 1,350 F, else you will absorb a lot of gasses.

.
 

L98fiero

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How much larger than the crucible does the inside of the furnace have to be, I have one I've been dragging around for 30+ years and it seems to be good size, I think it's considered a 10#, it's ~6" diameter at the top? I imagine there must be optimal clearances for diameter and probably height as well?
 

GreenTwin

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I have seen people operate a furnace with perhaps 1" clear between the crucible and the funace wall, but practically speaking, you will tear up your refractory trying to get the lifting tongs into a furnace that is too tight.

"They" say 3" clear for an oil burner melting iron, but I have seen 1.5" that works well.

I generally add some clearance inside the furnace so that I can use a range of crucible sizes.

For aluminum, the crucible number is roughly how many pounds of aluminum it will hold.
For brass or iron, a crucible will hold about 3 times more mass than aluminum, but with the same volume, due to the difference in metal density.

Below are the furnace dimensions I am currently using.
If a #10 is the largest crucible size that you will use, then you could downsize the furnace quite a bit.

Image7.jpg



NOV-2019-01.jpg




NOV-2019-03.jpg
 
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