Hi guys, Long time lurker, very infrequent poster. Let me introduce myself. I'm John DeArmond, Chief Engineer for
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.
And here are the ingredients
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 :-))
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.
Here is a photo of the melt ready to be fluxed, skimmed and poured.
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
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
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