THE MILLER FOUNDRY
 
 
 

 

 

ELECTRIC FURNACE

I am starting on my second furnace. Electrics are under-represented here so I thought people might like to see it. I would like to build a small electric furnace that could be used in my basement or garage with clean metal. So far the plan is to use a 1550 watt Kanthal element with and IFB surround to support it. I intend to make a 5" ID furnace to fit a 4" pipe size crucible using IFBs in a hexagonal shape. The furnace chamber will be 8-9" high. I hope that will be enough wattage to get to Al temps. I will eventually wrap the IFB core with ceramic wool and place it in a housing. I am going to try to build this "dry" without using any castables.
So far I have obtained the IFB and cut groves on the table saw. I stole this idea from Dan's workshop. Very clever.



More to follow.



My plan is to have only one brick with the grooves at an angle (Dan's idea). The angle brick will jump the element up to the next set of groves so I can spiral wind the element as you describe. It seems easier than cutting all the bricks with angled grooves. Think of a parking deck. Ill post pics when I cut it.

Better vote soon. Testing is imminent.



I stretched the element out to 90". I cut a firebrick with angled grooves to match the straight cuts I have already made. Then I put the whole thing together.





I hooked it up to 120v with high temp hookup wire.


I couldn't wait so I plugged it in to see what would happen.

It glows purple?!!! Obviously this is producing cold fusion. Eureka! I measured for neutron emisson but did not find any. Maybe it is just a camera artifact? I doubt it; its a Sony.

Lets throw a crucible in this thing and cover it with firebricks!


To be continued...I have to work early tomorrow.



Since it takes about an hour to get up to full temp (typical for an electric furnace), I have no plan to add a thermostat. Maybe just an on/off switch. Overheating will not be a problem.
My crucible stands about 6" high. I wrapped the coil to reach about 5" off the bottom figuring the coil would be right next to most of the thermal mass if the crucible was near full. Also the top of the chamber will heat by convection anyway.
The IFB's are very soft. I cut the grooves with 2 angle grinder blades stacked in my table saw to make a dado. I cut the sides of the bricks on my bandsaw with an old blade. You could do it with the table saw also.
I can recommend this method of construction so far. Simple and elegant. Durability, I don't know. The IFB's are kind of fragile.
Interestingly, I think this will be cheap to run. We pay about 10 cents/KWH. If I run this for 2 hours thats about 30 cents. That seems too good to be true. Maybe I have our rate wrong?
I will fire this up tonight and see if I can melt anything!


It took about 45min to start to melt and then I added a small ingot. That took another 15 min. Pics below:








I poured this into ingots easily.
I would probably have to let it heat some more to get a good mold pour. My furnace still has no outside insulation so it is loosing some heat there. I am considering dropping it into a propane tank housing with some ceramic wool. Thats all for now. Success!
R


I am considering the following modifications:
I may disassemble it and reduce the chamber height by 1".
Shorten the coil for higher temps
Coat the IFB with ITC100 or something similar to make it durable.
I will definitely add an insulated housing.
I have an infinite switch but Im not sure cycling the device on and off will be worth much.

COMPLETION:


It gets hot!


Furnace top and bottom


The housing (propane tank)


Finished furnace


Extracting liquid metal! Note the lid to the right.