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 .


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!

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?

[unfy]

Charcoal furnace is like $50 and an hour of your time.

Gas furnace is like $100 and 90min of your time.

Electric furnace is around $150-$200 and a weekend of your time in actual labor.


That said, element and range control arrived.  Element can do 2100F sustained without degrading itself.

Aluminum: 1221F
Brass: 1700-1900F
Gold: 1945F
Copper: 1983F
Silver: 1600-1800F

There's not a lot of other 'common' metals that are in this range sadly.  Ductile Iron is 2100F, and most irons are under 3000F - but these elements and construction materials can't safely hit those temperatures.  I dunno if there's an air breathing element that can hit 3200F (let alone what the cost of it would be).  I imagine a tungsten element could. The refactory / furnace walls would be a concern then as well.


I dunno if I've ever mentioned plans on what I'll be casting / making.  I honestly don't have any specific "right now" ideas LOL. 

Eventually I'd like to make some reloading press add on parts (case feeder for example). 

Being able to cast my own gears would be handy (use wood to make pattern then cast'em).

But basically... it's neat, I wanna do it, and it is a bit of a trade skill to learn heh.  I'm sure there's miscellaneous things that would be handy to cast.

[bkoenig]

Some 0% lowers would be neat....

[unfy]

Looks like for an air breathing element that can do iron you'd prolly want Zirocthal for 2200C (4000f).  I don't see pricing anywhere.

Graphite stuff appears to have an oxidation problem above 600C or so.  They do make coated graphite elements though.  Not sure on costs.  But graphite can hit 3000C allegedly....

Anyhoo, all of that is well beyond anything I'd have a desire to touch (at the moment at least).  While iron melting sounds really really really handy - it begs questions such as 'what would you make your tongs out of?'.  While i'm sure handling the crucible is short duration and stuff, but it still seems like a possibly valid question.

[unfy]

Some 0% lowers would be neat....

My initial casting will be based off of greensand flasks etc.

So it'd need to have a design where I can split it in half - put it in a box with a bunch of sand around it - then remove the mold.  There are some shapes that make the whole 'remove from sand' rather impossible

There's lost wax casting (a 1 time thing due to shattering the clay after the fact), or possibly if ya felt like milling stuff out of a higher melting point metal, etc.

[Phantom]

Unfy 
What are you doing for Air filtering or Venting in case of toxic or dangerous off gassing ?

[unfy]

Unfy 
What are you doing for Air filtering or Venting in case of toxic or dangerous off gassing ?

Thanks for mentioning this for folks.  I was intending this to be just a 'build' thread for the furnace, but sure a bit of safety is a good idea .

This will never be used indoors. It'll always be used outdoors.

But yes - you really want good ventilation.  While aluminum in of itself is harmless - if you're melting scrap or creating zamack / pot metal / aluminum-zinc alloy - you really must have proper ventilation.  Zinc / zinc fumes is toxic.  And depending on what you're doing - you'll want to make an aluminum-zinc alloy due to it's increased strength.


I'm currently facing huge dilemmas concerning how to cut the firebrick.  I really don't wanna do it indoors here at work due to the mess, but I really don't feel like buying a table saw.  The $45 tablesaw on CL aint quite what I want, asking owner of the $75 one.

The $129 cheapie menards table saws don't have long arbors on them, can't mount 3 blades on them at a time (to get to 3/8" cutting width). 

My cheapy angle grinder has left/right threaded holes for the additional hand grip.  I can use those to make something for mounting.  But I'd rather not.  And that'd still be just 1/8th inch blade-cuts at a time.

I can make some stuff so that I can go about using circular saw (I don't trust myself with circular saws, so i picked up another piece of 24x24 OSB to use as a platform to make guides etc).  Still just 1/8th inch cuts at a time, meaning 2-3 passes per groove.


edit:

Yeah, i'll just break down and use the table saw here at work.  At least I will assuming I've got blades for it.  It's 10" blades, 3 ish max depth at 90deg.  I know the blades i brought with me are only 7", but I'm pretty sure I've got some bigger blades at home. Yay for them being on sale months ago at Bargain Mart Tools on 84th (Papillion).

I'll be making fence/jig stuff tonight.

And oh look, I get to go to Menards for a THIRD time today. Forgot spade connectors for the range control ._.

[unfy]

Cat attacked me last night. Refused to get out of lap.

This morning, got initial plans done for fence/jig for brick grooving. I'll be making stupid stuff out of wood tonight heh.

The other masonry blades I've got are 9" - so all is well.

Brick grooving will have to wait until late tonight or sometime tomorrow (didn't bring shopvac for extra dust control, oops)


Got some 10-24 4" stainless screws from Fastenal,  and a bunch of 10-24 stainless washers/nuts from Westlake/Ace. The 10-24 all thread rods are cheaper but wasn't in stock and I'm an impatient guy at the moment heh.

I'm just not feeling comfortable with how big the 1/4" stuff (washers/nuts in particular) was going to be.  After the grooves are cut I can eyeball the 1/4" to see if it'd work.  1/4" is easier to come by than 10-24.


Talking to Tomasek about constructing a crucible out of steel for the furnace.  I guess I should also just bug folks here ?

Basically, I need a pipe 4-5" in diameter (preferably 4.5 or 5.0)  and 8" tall.  Then some ears on top of it with some holes for grabbing it.  And a plate welded to the bottom.  Made out of steel, I've heard schedule 40 does well.


edit: I'm beat tonight. Don't think I'll actually do any work on stuff and instead just go to bed early.  Groggy + power tools makes for bad !!! SCIENCE !!!

As per the PC oven thread - I'm grabbing a dryer tomorrow.  I really do think the motor will be 110.  Gas dryers use 110 for control and motors, so there's some sense in electric ones to use 110 for some stuff and 220 for high heat.  Anyhoo - assuming the motor is 110, a ball mill / tumbler will be in order.  Basically need to crush cheap no name kitty litter into fine clay for greensand.  Haven't decided what to use as the 'ball' / 'balls' part. Supposedly some kind of huge ball bearing is the intention.  I suppose some large rocks would work too... I dunno.  Some fear of them breaking ? *shrug* whatever - deal with it later.

[unfy]

Got the straight grooves cut in 5 of the firebricks.




Used this to keep things aligned / a hold of safely / dust control.

The cute thing about it is, I sized it for a tractor supply company brick.  Then added about 1/8th of an inch just in case bricks were different size.  Get to menards bricks - and that 1/8th wasn't enough.  Had to sand it down some to get'em to fix - and for the TSC brick, had to use some felt to keep it held true.

The picture is of it 'upside down', normally the brick would be facing down with the wood covering it.

I used felt to avoid scratching up the top of the table saw.




The first groove cut.  It works. Yay!




Something went wrong during this cut.  This was in the TSC brick that was just a bit shorter than the menards bricks - so it quite possibly got just a hair catty cornered.   Or maybe it hit a hard spot.  Or the blades got too hot or something.  It took *forever* to make the cut - and as you can see it was melting either the brick or the blade material.

When I started the next cut after letting things cool for 15min - it got about 1/2 inch in and started doing it again.  Stopped, unplugged saw, changed the order of the blades, viola - back to smooth cutting.




The straight groove bricks (5 of them, 5 grooves each) have been cut. Yay!

Sadly, when I started to inspect the burnt brick above - I noticed that I had somehow munged the measurements.  Which is really weird.  I was checking each measurement 3 times tonight.  Anyhoo, it caused me to need to change the other cuts just a bit.

This means that when it comes time to do the terminal brick (to connect all the grooves into a spiral) - I'll have to change the push block i've made for each and every of the 5 primary cuts on it (angles are all different).  Kind of a pain in the ass .

It took about 4 hours to cut those 25 grooves.  A large chunk of that was trying to sand down the jig thing and dealing with the burnt brick situation.


Tomorrow:

* need to bevel the groove side long wise of each of the 5 straight bricks (fast to do)
* need to also bevel the terminal brick

* figure out the lines for getting the spiral connections in the terminal brick (gonna measure not 3 times tomorrow, but 4(!@%$(!@%)!@%)

* groove out the spiral connections in the terminal brick

* groove out the two straight half/partial grooves of the terminal brick (one for each end of the element) ... this will be weird i feel.

* drill press the terminal holes in the terminal brick

* get the terminal holes drilled in the sheet metal shell (gotta carefully align stuff)

After all of that - in general terms,  it'll be getting the element and terminals in place as well as the rest of the electronics... then mixing the refactory cement and ramming up the pieces. From there... it'll be the week to dry out the refactory and a day to do initial firing.

I'm thinking that week of waiting while it dries out would be a great time to start taking apart the dryer for powder coat oven stuff as well as ball mill (for greensand) thoughts with it's motor (and/or drum) etc.

[unfy]

As noted in another thread I'll be moving to a place that has more limitations on what I can and can't do and stuff.

I'll still be building and finishing this furnace, it's just that all of it will now need to be done at work.