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Electric Shop Furnace Build (melting aluminum)
unfy:
This is what I'm basing my build off of:
http://www.dansworkshop.com/2008/03/homebuilt-electric-melting-furnace-2/
It's a $4 PDF and worth picking up if you have ever thought about this kind of thing.
It's based off Gingery's Lil'Bertha. Gingery's book can be difficult to find and will cost more.
The basic premise is to use some resistance wire to generate heat, and build a chamber to hold the heat so that you can get it to melt metal. Can be 110v or 220v.
Your wire choices would be mig wire (burns out pretty quick), nichrome wire (not bad), or kanthal a1 (better over all, and runs hotter). Temperature control (if desired) would be via an electric range infinite control (the knob ya turn to select range heater temp) or using a light dimmer and some SCR's (see the PDF).
For now, I've pestered Paul @ budgetcastingsupply.com for some info so I've bought a heating element and range control from him. In the future I'll be winding my own elements and making the dimmer/SCR temp control stuff.
It's taken me some time to gather everything. Been kind of 'a piece at a time' kind of thing over the last few months. But I've now got everything (or it's on it's way here).
Started with cutting some 1/2" pipe from the plumbing section of hardware store and then drilling the mounting holes:
The extra drill bit is in the other hole just so can align the holes.
unfy:
Picked up an extra piece of OSB and then got to work on today's tasks.
First up, using sheer at work to cut air ducting to make outside shell of the furnace. Two pieces together to double diameter. Smaller loops are the base and top, big loop is the chamber that will house the element.
The really big piece is what's left over. This includes cutting off the crimped end and throwing away a 3.5" piece from the tin snip attempt.
Then cutting formers out of 3/4 inch OSB. Used a rotozip style saw for this, but it probably would have been faster to use a jig saw. Ok, I know it would have been faster to use a jig saw. Granted, maybe I just dunno how to use a rotozip.
Next up: since I used a sheer to cut the metal, need to use a flat head screw driver or something to re-open the ductwork joint stuff so can make use of it. Then it'll be drilling holes in the ductwork for a myriad of reasons.
I need to look at the PDF again to see what it has to say about the lid and some other stuff. When drying out the refactory - author talks about using a hexagon piece of plywood a little bigger than the diameter of the firing chamber.... and place that between the firing chamber and the lid. I'll have to see if it mentions a thickness or what.
unfy:
Slept in a bit this morning. Still did some work on the furnace though. Also got confirmation that the heating element and range control have shipped \o/
Holes drilled in the base (right smaller loop) for the reinforcing wire along the bottom and all of the seams drilled and bolted. The base ended up having one piece cut at a tiny angle, so one of the seems doesn't quite meet up. Put the uneven seam to the bottom so that it won't interfere with joints between sections etc.
PDF doesn't mention thickness of the plywood to cover heating chamber when ramming up the lid. I'll use a 1/4 inch piece probably instead of the 3/4" from the formers.
Next:
Immediately: Drill holes in the base for mounting the legs. My *really* old and *really* cheap battery drill is giving up the ghost finally heh... so after the above drilling it was dead.
Later: fiddle with firebrick. I'll prolly attempt to use the sliding compound miter saw here at work. I need to take another look at it to make sure the arbor can handle 3/8's worth of blade attached to it. I'll also need to take a wire brush to it, it's been allowed to gather a bit of rust along the sliding portion :(.
unfy:
No pics this morning, maybe later in the day or something.
Tuesday night I attached the legs to the base, the handles to the lid, and the handles to the heating chamber body. Kinda neat to see it kind of take shape :).
I did go with some garage door handles for lifting garage doors - but I feel they are quite possibly too small. We shall see. Next furnace will make use of bigger handles for sure.
The formers above aren't perfect. The cut out section measures like 11 7/8. But the hole 'section' is like 12 1/4 or something. Soooo... I didn't have rotozip saw thing set quite right. I'll be eyeballing the hardware store for some kind of think plastic / rubber strip to attack to the inside diameter to bring it back down to 12".
Brought the masonry blades to work, went and eyeballed the sliding compound miter saw. It can't do three blades stacked on top of each other :(. The two table saws can (one of which I don't trust). I'll probably end up picking some evening or morning and giving it a go on the table saw.
While 5 of the fire bricks to be grooved are straight forward - I still plan on making jigs (or whatever they're called in this case) for passing them over the table saw. The 6th / odd man out / terminal brick requires some weird angles and such -- so it's screaming for a jig. Especially with my desire to make more of these furnaces in the future :D.
Dan's PDF has ya use the pre-mixed mortar to mix with perlite for the refactory. I'm using a dry bag that I assume chemically sets.
Dan suggests mixing an 8qt bag of perlite with 1/2 gallon of the mortar at a time.... and since the drying action causes it to set rather than chemical stuff: you can store it. Not quite so much by bag set. I'll be calling the manufacturer to confirm this later today.
Assuming it is chemically set, I'll need to do some math on how much to mix at a time for each piece. Online calculators for volume and such here we come! :D
Ya ram up the base, let it cure for an hour, then set the heating chamber on top of it and ram up the heating chamber, let it cure for an hour, then ram up the lid (this way the seams are all 'perfect'). The suggested working time of the Akona stuff is 1 hour so can't just make a bunch and then sit / wait while things cure.
edit for self:
Element I bought has a minimum operational length of 60" and a max of 120". At about 3-3/8" per firebrick, a hexagon gives 20-1/4" per diameter there abouts. Therefore I need between 3 and 6 grooves in each brick. 4 or 5 looks to be the about right - I'll go with 5. Even if I end up with 3.75" per firebrick face that's still 112" of length total (under 120).
Dan's book says 6 groves in one place, a diagram for 8 grooves, and then a picture of bricks with 7 grooves cut. *sigh* heh.
addition:
Called TCC here in Omaha (local Akona folks) - the answer... was a bit confusing. I'll just treat it as a chemical set mix, mix only what I think I'll need. Anything extra I'll store in an air tight container to see if it hardens on it's own or if does set only by drying out.
bkoenig:
Cool. I figured to melt aluminum you'd need a gas fired furnace.
I know you said before, but I can't remember - what are you planning on casting with this?
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