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View Full Version : Calling All Engineers! Plasma Arc Furnace



Dendritic Xylem
03-29-2010, 07:40 PM
I'm an advocate of anything diy and thought perhaps some of the members here could pitch ideas for building a homemade arc furnace on the cheap.

I know you can make small arc welders from microwave transformers. Could this be utilized for our project?

I saw a couple of homemade units on ebay selling for $250-300. So we should be able to make it for half that, right?

Temp control will be necessary since these things have no problem melting platinum.
Could a heavy duty potentiometer do this until we can fit a digital pyrometer control?

Please.....vent your creativity. :D

theFool
12-16-2010, 08:36 PM
Have you seen this site? http://www.metallab.net/arcmelt.php
He uses an electric welder and carbon rods taken off from batteries.
Also in this site there is info on simple electric furnace, regulated by variac.

Dendritic Xylem
12-17-2010, 04:16 AM
That's a good find!

Here is a patent for an unorthodox fire assay procedure using plasma arc and iron as a collector.
http://www.patentstorm.us/patents/5238485/description.html

Most assayers use gas or electric furnaces and lead or bismuth as a collector of the precious metals.
Many believe this procedure extracts most of the precious metals.

The method outlined in the patent produces yields multitudes higher.

Aleilius
12-17-2010, 02:28 PM
I would go with the microwave transformer based arc furnace. You need to find a beefy microwave transformer though. A lot of the microwaves produced today are quite weak in comparison to microwaves produced 10-15 years ago. I've had a chance to experiment with them about 10 years ago. The arc produced is very intense. If you need more power these transformers can be wired parallel, or series. They draw a lot of power though. So powering two or more on a line with a small breaker will probably cause it to trip.

I'd look into finding a variac that can handle high current/loads. Adjustment of the variac should allow for some temperature control.

Dendritic Xylem
12-17-2010, 06:12 PM
Thanks for the input Aleilius

How far apart could the electrodes be spaced using a 1200W microwave transformer, and alluvial black sand as a medium? I realize this is kind of a specific question, I just have no idea what kind of arc lengths can be accomplished with these materials. Probably depends on the properties of the sands.

Aleilius
12-18-2010, 12:07 AM
Thanks for the input Aleilius

How far apart could the electrodes be spaced using a 1200W microwave transformer, and alluvial black sand as a medium? I realize this is kind of a specific question, I just have no idea what kind of arc lengths can be accomplished with these materials. Probably depends on the properties of the sands.

Hey, the problem with microwave transformers is their relatively low voltage (~2kv). In order to start an arc the electrodes need to be spaced about a millimeter. Once the arc is started it can be drawn to roughly an inch or two. I'm really not very sure about any specifics regarding using black sand. Sorry!

One thing about using a variac is that it is a source of variable voltage. When the variac is turned down you'll probably only get a few hundred volts out of the transformer (which isn't enough to start an arc, or to sustain it). I think a variable current source would be best in this instance.

I'm kind of out of my league here though. Just tossing a few ideas out there. I'd also love to make an arc furnace myself! I'll be interested to hear what you learn from this research, and how you'll proceed.