Casting fun

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awake

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Kitchen metallury: It is like making coffee pots out of sugar, it works for some time. The coffee will be sweet and eventually it creates a mess. :) That is why most people do not use sugar for making coffee mugs.
Okay, now I REALLY WANT to make a coffee mug out of sugar! :)
 

awake

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That looks like a plan. Hmm ... do I need to clear the PLA out of my 3d printer first, or ... ?
 

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.
 

CFLBob

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even printed sand moulds are possible now ....
Now that's genuinely useful, but it looks like a big, ferociously expensive machine for a hobby machinist. I really can't see being able to do that at home anytime in the next 20 years. That makes it less interesting.
 

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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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. …
 

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