countertop aluminum foundry

Hi guys,
Long time lurker, very infrequent poster.
Let me introduce myself. I'm John DeArmond, Chief Engineer for
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, a company that manufactures low cost induction
heaters. My personal interests are non-ferrous metal casting and
glass blowing.
My business and personal interests came together after we received
several requests for a small induction heater metal melting furnace. I
decided to design a small table-top-usable furnace and see how it
worked. Here is the result.
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And here are the ingredients
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For obvious reasons, I call it my Kentucky Fried Furnace :-)
The crucible is a squat disposable propane tank with the top cut off.
On top of that is a blanket of Frax to electrically insulate the
crucible from the winding that follows. On top of the Frax is a
winding of fiberglass tape to hold everything in position. In use the
tape melts away but that doesn't matter because the refractory holds
everything in place.
The refractory is Kast-O-Lite. This was some 3000 deg rated stuff
that I had laying around the lab. It isn't the right refractory for
the job (relatively high thermal conductivity and high thermal
expansion coefficient) but it works adequately.
For the first melt I decided to set it up in my kitchen (yes, I'm
single :-))
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From left to right, a power meter to measure the power consumption, a
yogurt cup containing stuff to melt, a little white cube that is an
Onset Hobo 4 channel thermocouple data logger, our Roy induction
heater, an induction range with a batch of iced tea brewing and
finally the furnace.
The crucible holds about 6 lbs of aluminum and with the 1500 watt Roy,
takes about 18 minutes to melt, using between 1 and 2kWh (about a
$0.25 worth of electricity at our local rate). Using our soon to be
introduced Roy 2500 (pictured), the melt time is reduced to around 9
minutes and using the same amount of power.
Some aluminum parts during the melt.
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Here is a photo of the melt ready to be fluxed, skimmed and poured.
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As you can see, the Kast-O-Lite cracked despite my following their
casting and curing instructions to a Tee. It's also too thermally
conductive, allowing the surface temperature to rise to around 500 deg
F by the end of the melt. Nonetheless, the furnace is lightweight and
the whole thing is picked up wearing heavy welding gloves to make the
pour. My aim with the proper refractory is to keep the surface
temperature below 200 deg F.
I put a large worm gear pipe clamp around the top of the unit to
prevent the crack from expanding. After several melts, it has
remained about the same.
On Monday I'm going to talk to our guy at Larkin Refractories
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about an appropriate
refractory for this application.
This has worked well enough that I've ordered materials for a 20lb
furnace to be built into a 5 gallon steel pail. I'm using this ladle
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as the crucible. This unit will use a 3500-4000 watt heater to keep
the melt times in the same ballpark.
So now my businessman instinct kicks in and I wonder if there is any
market interest in small furnaces that can be used indoors and without
any special ventilation. Let the discussion begin.
John
snipped-for-privacy@fluxeon.com
John DeArmond
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Tellico Plains, Occupied TN
See website for email address
Reply to
Neon John
Loading thread data ...
Probably worth your while subscribing to and posting to the mailing list
snipped-for-privacy@Yahoogroups.com
Reply to
Stuart
Thanks for mentioning this. It looks to me like a $1000 investment overall which exceeds my need to cast rather than machine aluminum parts. What would be the appropriate size/weight range for 60-80 KHz? -jsw
Reply to
Jim Wilkins
As an alternative take a look at
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some other URLs that might be of interest
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Reply to
F. George McDuffee
"F. George McDuffee" wrote in message news: snipped-for-privacy@4ax.com...
My approach was to buy small fixer-upper lab ovens at auctions, and second-hand temperature controllers. I designed and built electric industrial ovens for a living once. However I've used the wood stove for my few casting experiments. Right now a new crucible is drying on top of it.
I stored the crumbling aluminum degassing tablets a foundry supplier gave me in my vacuum oven, which I use as a dry box. When I opened its door this afternoon a sharp, biting odor came out so the pellets are in a baggie now. I don't think I would drop them into molten aluminum in the kitchen.
-jsw
Reply to
Jim Wilkins
If your mad-scientist lab gear includes old Variacs, I found that the hundred-dollar brushes are rebuildable when they wear short. These people will glue in a new carbon with silver epoxy, or a DIY one can be pressed in.
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I bought 1/4" thick carbons rated for 120V (bulk resistivity) and milled new brass holders to press them into, with the milling vise, then narrowed the contact ends to match the originals. The carbon chips easily and climb milling worked better. I made several of the cuts with a less risky razor saw and file.
-jsw
Reply to
Jim Wilkins
Not to take too much wind out of your sails, but couldn't you achieve the same thing using very much the same construction, only wrapping the crucible with plain old heating coils instead of the induction coil? Then just apply 220V and watch melting happen?
I do like the idea of a cheap integrated crucible and furnace -- it seems to simplify the task.
Reply to
Tim Wescott
Would your controller be able to hold the casting at 540C for solution heat treating?
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-jsw
Reply to
Jim Wilkins
Fascinating stuff. However being in the UK I suspect the cost of shipping and customs would make it a trifle expensive. i would need to look to sourcing parts within the UK if i were to build one.
Reply to
Stuart
Neon John,
I did look around your induction heating websites, and $750 for a MRO induction heater ain't bad, but I never did find out the operating frequency or frequency range.
Joe Gwinn
Reply to
Joe Gwinn
Yes, that is my problem too. I already have enough stuff to keep me busy well into early summer next year.
Reply to
Stuart
I use a '30'gallon tall boy propane bottle and torch in the bottom of my furnace. Otherwise it is about the same, but I use a stone like refractory.
AL and Bronze/Si.
Martin [ yes I know 2014 November, it has been a while since I melted metal myself. ]
Reply to
Martin Eastburn
snipalot
I'm using a short piece of 4" diesel exhaust tubing for my small "crucible" and a piece of 4" square tube for a bigger one for aluminum . Handmade clay for brass and bronzes . My furnace is cast refractory in a 5 gallon solvent bucket heated by a naturally aspirated propane burner . Burner is based on the Reil burners , but I'll be building a new one based on Mike Porter's new design for higher temp melts . When I find my round tuit I'll build a smaller furnace for brass/bronze , the crucibles are smaller and don't heat well in the "big" furnace . BTW , Neon John posts on the castinghobby email group , and last I heard they had made advances on small induction furnaces .
Reply to
Terry Coombs

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