countertop aluminum foundry

Hi guys, Long time lurker, very infrequent poster. Let me introduce myself. I'm John DeArmond, Chief Engineer for http://www.fluxeon.com , 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.
https://www.dropbox.com/s/k50wn0imdjwvwgs/01_furnace.jpg
And here are the ingredients
https://www.dropbox.com/s/bgf3mvu471z0dv0/02_furnace_parts.jpg
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 :-))
https://www.dropbox.com/s/g8fv2jtwl8fb3qa/03-Kitchen_foundry_Overall_view.jpg
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.
https://www.dropbox.com/s/pjoyf8lub920ppu/04-Melting.jpg
Here is a photo of the melt ready to be fluxed, skimmed and poured.
https://www.dropbox.com/s/3pybr8emgnmuovy/13-The_melt.jpg
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 (http://www.larkinrefractory.com/index2.html ) 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
http://www.dykast.com/products/605dl-6mb-20-lb-aluminum-capacity/2916
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 http://www.neon-john.com http://www.fluxeon.com Tellico Plains, Occupied TN See website for email address
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Probably worth your while subscribing to and posting to the mailing list
snipped-for-privacy@Yahoogroups.com
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Stuart Winsor

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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
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On Sat, 1 Nov 2014 16:40:24 -0400, "Jim Wilkins"
<snip>

As an alternative take a look at http://tinyurl.com/jwrxdq5
some other URLs that might be of interest http://tinyurl.com/q4ms86s http://tinyurl.com/nmh3apm http://tinyurl.com/pydwv5f
--
Unka' George

"Gold is the money of kings,
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message wrote:

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
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wrote:

Would your controller be able to hold the casting at 540C for solution heat treating? http://benthamopen.com/tomsj/articles/V002/6TOMSJ.pdf
-jsw
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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.
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Stuart Winsor

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Yes, that is my problem too. I already have enough stuff to keep me busy well into early summer next year.
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Stuart Winsor

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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
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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. http://www.carbonbrush.com/
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
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On Fri, 31 Oct 2014 20:16:17 -0400, Neon John wrote:

Kitchen_foundry_Overall_view.jpg

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.
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Tim Wescott
Wescott Design Services
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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. ]
On 11/1/2014 9:29 PM, Tim Wescott wrote:

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Martin Eastburn wrote:

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 .
--
Snag
Working intermittently on the patterns for a Gingery shaper ... spring is a
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