# Melting and casting metals...



## MrCrankyface (Jun 17, 2022)

FIRST THE BACKSTORY...
I needed to melt some silver to make a small jewelry piece for my wifes birthday.
My budget was absolutely 0 and I definitely did not have time to make a proper foundry/furnace.
Of course this also means I can't spend the money on buying one that already works(which in hindsight would've saved weeks of time, and money).
My first try was using just a propane torch, a bucket and some stonewool insulation.
I probably don't even need to mention that it did not work.
The insulation melted and the propane wasn't strong enough to reach high enough temps, fast enough. 

I realized I needed a better container that would keep more heat inside and wouldn't melt on me...
Having seen enough youtube videos, I started looking for those white firebricks, which turned out near-impossible to buy in Sweden.
What I ended up buying were these 50mm thick, 230x114mm, "fire-resistant bricks".



From what I've gathered afterwards, whilst they are fire-resistant, they're also horrible as insulation compared to the white firebricks.
They're also crazy hard which makes them difficult to cut and shape, ruining my budget and project-time further.
Either way, managed to find a diamond blade($$$)that fit on my chopsaw, from previous experiments I knew I had to use watercooling, so that was made from a windshield washer pump.
Hastily folded up the metal sheet everything is sitting on to control the waterflow which drips into a second container on the side.





Many, many, many MANY hours later, I managed to get this together.
Each piece has been cut at an angle to get a smooth and even contact all around.
Further more, slots have been cut along the inside for kanthal wire(heating wire).
Initially I was still going to use propane but decided to go all in now that I've already wasted a bunch of money on bricks and mortar...



Using special fire-resistant mortar I tried putting all of this together, excuse the mess, it's the first time I'm playing with stuff like this.
Put it on both between the joints and also on the outside(for unknown reasons, pretty sure I just got carried away like a child with ink markers. )
A few hours into it as it started to solidify, I went around and smoothened it out with 80 grit sandpaper on a plank.
Still had some weird issues where the white areas are dead hard but the darker areas never became hard and are still kinda dusty to this day(several weeks later).
On the left you can probably see all the through-holes for both heater wires and temperature sensor.




Really just shooting from the hip I made up a lid whilst I was at it, reinforced the mortar with some steel wire in a crosshatch pattern to hopefully help this hold together.
Made a hole in it since all furnaces you can buy seem to have it. Not sure if it's because you need airflow or if it's so you can feed in new material without lifting it.



The amount of stress, wiring this up, and on the first startup, hoping it's not going to explode. 
The SCR-dimmer was to control the amount of power on startup as I wasn't sure how much I would need to make the heater-wire glow.
Too little and you're not getting enough heat, too much and you'll burn it off.
First attempt was with 230 volt AC(1phase to ground, ~1800W input), this was enough for 200-300c, so far from what I need/want but at least let me slowly heat it up during first testing.
Second attempt was with 380 volt AC(2 phase, ~4900W input), this is the second heatup you can see in the video.
Luckily I got the length of the coil just right so I don't need the SCR-dimmer. It seems to get just hot enough with no limiter.





I've still only run it up to 200c or so since it's recommended to keep it at lower temps for a few hours to get trapped moisture out etc.
Thing is, even after this short run I could already tell the outer surface was heating up way too much, so going up to 1000c without modifications isn't going to be a good idea. 
Furthermore you can probably tell the mortar has cracked just from those heatups. Not sure if that's normal or I've done something wrong.

So next little experiment is to insulate the entire thing. I ordered some ceramic insulating stuff that never arrived and has since moved on to the idea of trying "perlite cement".
The idea is to have an outer case of sheet metal which contains the furnace and any volume inbetween will be filled with the cement.
I have a bunch of 1.2mm sheet pieces that used to cover some installations, they also already have a handy ledge at the bottom which I figured I could flatten out and shrink to create the curvature needed.
The bottom plate is a bit thicker thread plate aluminium hence why it's riveted and not welded. I'm just using scraps hence the possibly weird choices.
The picture doesn't do it full justice, but no matter what I did it was just insanely wonky all around and I couldn't get it to maintain a smooth/round curvature because the sheet itself was fighting against the shrunken lower ledge.



This led to a complete rethink again.
I made a roller for rolling sheet stock ages ago, but it only takes 30cm wide strips, about half of the height of that thing.
Either way I ended up cutting the lower ledge off, splitting the sheet down the middle and extending it so it would be longer than the circumference of the bottom plate.
After rolling that a few times I cut out new bottom and top ledges to finish it off and give some structural stability before welding everything together.
Still not 100% but way better than it was, and good enough for this cause.



So that's pretty much where I'm at currently.
3+ months behind on time and I'm not even going to count the money I've spent on this, trying to save money.
I'm currently printing these black pieces, to help me keep everything in the right placement as I start filling it with perlite-cement.
Most likely I will cast it in two stages, first fill the bottom cavity, within the bottom black piece.
Once that hardens a bit I can remove the 3d-print and put the furnace on it, then fill the rest of up to the brim.
The top black pieces makes sure I can get a layer of perlite-cement ontop of it as well, without spilling into the furnace.
Once it stiffens up a bit I will remove those pieces as well.



So what's left on the todo list?
-I want feets on the bottom to distance it from the floor/table/whatever.
-Some kind of hinge is needed for the lid.
-I'm not sure if I'm even going to use the current lid or just cast a new one completely from perlite-cement.
-Electronics need a fail-safe so the coils turn off if anyone lifts the lid(both dangerous heat and electric power)
-Since this is turning out quite chonky I want it to have at least 2 carry-handles on the sides.
-All the electronics needs some kind of box to stay in
-I need a bigger crucible for later when I want to melt aluminium
-Definitely need special tongs to grip the small crucible I have for silver, can't afford any mistakes once that thing is hot as a spill might be disastrous.

So stay tuned, hopefully I'll get this working within a few weeks.


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## Cadillac (Jun 17, 2022)

Mapp gas burns hotter than propane. I inject a airstream with the gas to the burner to get a hotter burn. Kaowool works great for insulation.


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## ddillman (Jun 18, 2022)

That is a very nice write up on your project. Thanks


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## MrCrankyface (Jun 18, 2022)

Cadillac said:


> Mapp gas burns hotter than propane. I inject a airstream with the gas to the burner to get a hotter burn. Kaowool works great for insulation.


Yeah I tried using a second mapp burner at the same time, but still didn't get the heat needed due to my bad setup.
I've heard of kaowool but seems impossible to get around here.
Going full electric now though and the perlite-cement seems promising.


ddillman said:


> That is a very nice write up on your project. Thanks


Thanks!

Further progress yesterday/today.

Sifted the perlite I had since there was a lot of fine dust in it, I think it will be much more efficient as an insulator if I get rid of that.
Then I measured up a 1:10 ratio of cement : perlite, in volume.
I've noted down what each weigh per liter, then I use the scale to quickly and accurately get the required volume.
First mixed up the cement then added in the perlite and tried to adjust the mixture by adding some water since the perlite will absorb a lot of it.
Ended up with a gravel-y slurry that seems to hold it's shape well, we'll see how strong it ends up..
The slurry weighs surprisingly little when you're used to "regular concrete".  
For reference, that amoutn of cement is 515gram whilst the entire container of perlite is 427 grams.




Here's the little 3D-printed mold to get a foot of sorts, for the foundry to sit on, before I pour in the rest.
I could probably have done a better job of compacting it after I filled the mold up..
I removed the mold after 24 hours and it seems to have stiffened up quite well and still holding a fair bit of moisture.
It also had a cover on top of the mold for those 24 hours to keep the moisture in, as I've read it helps the final strength if you let it harden real slowly.
Some pieces outside of this "containment" had turned white and seemed fully hardened, the strength wasn't impressive but should be enough even in that "quick harden" state.




So about the todo-list and lifting handles.
This is probably going to weigh 50kg/110lbs when finished so why even bother lifting it.
Instead I started making a little cart with 2 wheels and a foot/pad.
Should make it easy to move yet stay still when you leave it.
The idea is to just put in a handle on the wheel-side so you can "angle it up" and roll it like a two wheel handcart, obviously when it's cooled down.


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## rwm (Jun 19, 2022)

Both of these furnaces look great! Each will have a good use. My first casting furnace was also dense firebrick (easy to get.) This works, but has high thermal mass. You might consider removing the wire and using it as an air/propane or oil furnace where the thermal mass is less of an issue. These larger crucible furnaces are more suited to larger volumes of aluminum or brass. 
For silver jewelry, I would recommend a pouring ladle and an oxy/propane torch. You can just melt the silver (or small amounts of any alloy) in the ladle by direct heating with the torch and then pour it. Easy!


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## MrCrankyface (Jun 19, 2022)

rwm said:


> Both of these furnaces look great! Each will have a good use. My first casting furnace was also dense firebrick (easy to get.) This works, but has high thermal mass. You might consider removing the wire and using it as an air/propane or oil furnace where the thermal mass is less of an issue. These larger crucible furnaces are more suited to larger volumes of aluminum or brass.
> For silver jewelry, I would recommend a pouring ladle and an oxy/propane torch. You can just melt the silver (or small amounts of any alloy) in the ladle by direct heating with the torch and then pour it. Easy!


Thanks! It's one and the same as you'll see soon, I'm just making things difficult for myself.  
It is quite oversized for the initial job of melting silver, my reasoning is that if I was gonna build a foundry/furnace I might as well make it big and strong enough to also melt a lot of aluminium as that's something I want to do in the future.
I really want to invest in a oxy/prop or oxy/acet setup but just the oxygen bottle is almost twice the cost of this entire project(even at this current run-away stage).
The thermal mass is definitely one thing that annoys me, but we'll see how big of a factor that is once it's up and running, I think the power input is quite large compared to other "DIY electric ones" I've seen online.
Was your first furnace also electric or did you use some kind of fuel for it?

So todays work:
Finally went around the entire 'big bucket' and ground down the welds somewhat. Trying to remind myself that it's a bucket and not a show car, so I don't get carried away. 
I also riveted the bucket to the undercarriage so it can't slide around, but can be drilled out and removed if I need to for some reason.
The firebrick foundry then sits on top of the previously shown cement-perlite footing, which is then followed by a thick(8-10cm / 3.1-3.9") outer layer of more perlite-cement. I'm hoping the outer steel layer will be insulated enough to be touchable.
Two 3D-prints then slide into each other to make a tight seal on top, for two reasons:
1. Make sure I don't accidently fill the center with perlite-cement.
2. Get some support for the added layer of perlite-cement ontop of the hard bricks which will be roughly 3cm / 1.2".
Semi-funny side-note, I bought a HUGE bag of perlite, 100 liters. I figured this would last me a lifetime(and bulk is so much cheaper).
The second picture is how far I got with it, after my wife stole some of it and I sifted a lot of fine dust out, literally just missing a few centimeters. 
So off to the big-box store to buy smaller containers that are 10x as expensive just so I could finish up, I was missing around 10 liters of perlite..
Once poured in, I've tried to just compact it lightly, I don't want to smash it down but I also don't want voids/barely contacting cement.




Cement definitely isn't my cup of tea, or something I'm remotely used to working with, but I've tried to get a decent finish on top...
From what I've read you're supposed to let it sit for a bit, and then you can try to improve the finish, gonna give that a try in an hour or so.
I was surprised by how much I needed to mix just to fill this thing, I must've made like 10 buckets at least, the volume was a bit deceiving.
To anyone trying something similar, get/borrow a proper cement mixer, doing all of this with bucket and drillmixer was horrible and I suspect it also damaged the perlite at times since it's such a rough process.
Also, the last pour/top layer is slightly more cement in the mix, around 1:5 instead of 1:10, the idea/guess here was to make smoothing easier and also have a stronger surface/top layer.
The 3D-print will probably be heated up and removed to be as gentle as possible to the perlite-cement, I'm guessing it's gonna stick quite hard since I forgot to add draft angles..




I've covered it in plastic to keep the drying rate as slow as possible, so I'll be trying to not touch this thing at all for a week or so now..
There was some perlite-cement left over from the last mix so I made a little cupcake and another weird little shape so I can see how they hold up in a few days.

Regarding the whole gas/fuel/electric choice/discussion.
I know a lot of people really favor the gas/oil powered ones, and I'm sure they're both faster and more powerful, but they also scare the sh*t out of me. 
I'm hoping this will be a more "fool-proof" design where I can just set it to 800c and chuck in my crucible with aluminium to be melted, and not have to worry so much about open flames, hot gases(obviously there will still be some, but less), whatever fuel I would be using etc.
I believe the one I saw melting copper(1085c melt temp) only had 1.5-2kW input whilst this has 5kW and the wire should be capable of 1200c, 1300c if I'm OK with a much shorter life span.
Time will tell if I've made the right choices and if my research is correct or just wishful thinking.


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## Firstram (Jun 19, 2022)

With todays fuel prices, unless you're burning waste oil, electric might cost less to operate. Looks great!


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## BGHansen (Jun 19, 2022)

Watching your thread.  I've thought about investing in one of these kits off Amazon in case I ever get into making engines and want to cast flywheels.

As mentioned by Firstram, you may look at the cost of electricity vs. gas.  I made up some 1/2" diameter punches and 1 1/4" dies a while back and flame hardened them with an oxyacetylene torch.  I noticed my acetylene tank dropped about 25 psi.  The last fill to 300 psi cost about $100 or about $8 per 25 psi.  I've gone to using a Thermolyne muffle furnace which draws about 2000 W.  It takes the furnace about 30 minutes to get up to 1600 F (cherry red steel temp).  Our electric rate is about $0.13 per kW/H.  Difference for me was $0.13 for electric vs. $8 for acetylene.  Of course, propane is a lot less than acetylene.

Bruce


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## rwm (Jun 19, 2022)

For jewelry casting you can use the bernzomatic disposable oxygen and propane cylinders. Not sure if they're available where you are though? You can get multiple melts of a jewelry size casting out of one oxygen tank like that. In the US I think those tanks are around 10 bucks.


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## rwm (Jun 19, 2022)

not trying to discourage your furnace build. I have several large crucible furnaces. It's just that I would never use them for jewelry..


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## Cadillac (Jun 19, 2022)

I use propane with a home built burner fairly easy to build. Then I use a separate air line and inject about 10psi of air. my forge is a 40pound propane tank Lined with 2” of kaowool insulation. Takes about 15 min to get up to temp for aluminum. I usually do multiple pours since I have everything going. A 20pound propane tank last a long time for me. Could probably do a dozen or so melts on one tank. I was surprised at how Long tanks lasted. 
 I’ve seen where with a cement perilite mix they cure the kiln by running it on a medium heat for a extended period of time. Idk I also thought they skimmed the surface with a different mix maybe some ceramic based stuff to reflect the heat?


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## MrCrankyface (Jun 20, 2022)

rwm said:


> not trying to discourage your furnace build. I have several large crucible furnaces. It's just that I would never use them for jewelry..


I get your point and appreciate your point of view.
If jewelry etc was a more common occurence, and smaller bits, I would definitely go down that route.
Currently the silver-bit is a one-off project whilst 99% of the useage will most likely be melting aluminium, brass and possibly trying copper.
Furthermore the thing I want to cast is nearly 300 grams of silver, if I remember correctly.
Just by instinct it feels like a lot to melt with a small-ish torch, granted I have no experience in that department.

I have been looking around though, because a good torch has a lot of use for what I do, but the cheapest budget-level "kit" is >$200 here, and replacement bottles are then another $35 or so, quickly making it real expensive.
In the sense of long-term cost I think an acetylene/oxygen setup would be the cheapest, at least I already have most of the kit for that, but still quite expensive compared to just running the electric furnace(especially with solar power in the near future).




Cadillac said:


> I’ve seen where with a cement perilite mix they cure the kiln by running it on a medium heat for a extended period of time. Idk I also thought they skimmed the surface with a different mix maybe some ceramic based stuff to reflect the heat?


There's definitely a bit of a procedure on initial startup.
My current plan is as following:
-Cure/harden for a week whilst controlling the moisture(so it doesn't dry out too fast)
-After a week let it sit at 150c or so for at least an hour and monitor what happens, if anything happens.
-Progressively start increasing by 100c or so and let it sit at those temps for a while.

Should help get the last moisture out, as carefully as possible, whilst also giving me plenty of time to see if any problems show up.
The big danger is going too hot too fast, with moisture still trapped inside, basically making myself a little steam-powered bomb. 
I'm relatively sure the worst that could happen is that it cracks excessively, but patience is key, both for a better final result and for me to get comfortable with it as these are temperatures I've never been close to playing with.
I googled around a bit regarding ceramic refractory, and that could be something to try to be honest, reflecting more heat back towards the crucible might be good from an efficiency point of view.


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## rwm (Jun 20, 2022)

I am sure it will work fine for your first furnace. Even commercial refractory develops cracks so don't let that worry you. The long term issue with using cement is durability. The cement/water reaction is reversible at high temps and the cement will fail. Commercial refractory cement is different and will last a lot longer. You will do fine for aluminum but getting to brass will damage the lining. 
Yes 300g of silver is a big chunk and that would be crucible furnace size. I am not sure how cement will do at silver temps. BTW, one good thing about using electric is avoidance of gas porosity. Please keep us posted on your work.


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## rwm (Jun 20, 2022)

Here is an old pic of my first furnace using dense firebrick and insulating wool. propane fired.



It is not really necessary to fill in the gaps in the brick with mortar as you did, but it won't hurt anything. That will almost certainly crack though.

Also, I assume you are here?








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## kcoffield (Jun 20, 2022)

If you haven't already, consider joining www.TheHomeFoundry.org. I'm a forum Admin and there are all kinds of casting disciplines practiced there along with many examples of practical home/hobby solutions for foundry equipment.

I have several furnaces but the most often used is a low mass, 10" bore, 8kw, resistive electric. It can accommodate an A20 crucible and will melt 10lbs of Al in an A10 from a cold start in under 30 min. I think electric is a superior heat source for hobby aluminum casting because the furnace atmosphere is never worse than air and in practice quickly becomes oxygen depleted air, which is a great furnace atmosphere for aluminum. Not having to store fuel and being able to flip a switch is great not to mention very low melt costs......pennies.

With careful (lean) tune, you can certainly get good aluminum quality melts with propane, but one thing you can never evade is the massive volume of atmospheric air that is forced through the furnace and the melt is exposed to any/all humidity along for the ride which can be detrimental to (aluminum) melt quality.

Downside of electric is the limited operating temp. At the outside, you may be able to do some bronzes, else you're limited to low melt point metals. Fuel fired furnaces are most sensible for bronze/iron duty hobby furnaces. Induction furnaces are better for everything but unless you only want to do relatively small melts, cost, power, and operating complexity can make them impractical for most hobbyists.

Best,
Kelly


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## MrCrankyface (Jun 20, 2022)

Alright so as I suspected, I ended up making a new lid, which also gave me an opportunity to document the process I used for the bucket as well.

Several strips are cut, cleaned and welded together to make one long band, at least slightly longer than the circumference of the lid.
A thick aluminium bar with a convenient ledge on it is underneath, helps align the pieces.
Weights on the sheet just keeps it down to free up my hands.



Absolut chaos in the background, sorry about that, quite behind on cleaning up.
Either way the strip gets sent around a couple of times in my real ****ty roller.
The radius is quite forgiving, as long as you get it vaguely close to what you want to end up with, you're good to go.
Also the welds need to be blended decently to roll nicely.



A brim was cut from the cutout from making the buckets bottom brim, roughly tacked on.
Unfortunately I was tired and started making mistakes here by taking shortcuts.

I had already tacked it halfway around when I noticed the brims outer diameter was larger than the rolled ring, definitely not close enough for me to "hide" it.
Stupid call of the moment was to cut the ring and keep tacking, makes problems further down the road.



Here's todays little experiment.
I tried rolling this in an english wheel to get some shape to it.
Overall finish is pretty garbage, but for my second try ever I'm pretty satisfied.
This is however when the ring/brim mismatch showed up.
The lid was matched to the ring and is now too small because I increased the size of the ring to fit the brim...
Instead of taking a step back I just kept tacking, trying to force things into place.
Considering how thin the steel is on the top it's amazingly strong now when it has some shape to it, easily pulled everything else out of shape.  
Live and learn I guess.



So now I have a furnace that looks like some droid from star-wars.
I put the foil back on after taking the photo ofc.
Also it was horrible trying to lift the now HEAVY furnace off the workbench, but once down I'm real happy with the wheels on it.
The entire lid will be filled with perlite-cement, maybe also some kind of reinforcement to help it stay in place besides the brim piece.
I made the diameter as such that the steel brim is several centimeters away from the firebricks(super warm), so it should be perlite-cement on perlite-cement(less warm).


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## MrCrankyface (Jun 21, 2022)

rwm said:


> Also, I assume you are here?
> 
> 
> 
> ...





kcoffield said:


> If you haven't already, consider joining www.TheHomeFoundry.org. I'm a forum Admin and there are all kinds of casting disciplines practiced there along with many examples of practical home/hobby solutions for foundry equipment.



Lots of good info! Haven't seen that forum before, will check it out!


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## rwm (Jun 21, 2022)

I will be curious to see how long it takes to melt aluminum in that design. Electric is typically slower than fuel fired and that has pretty high thermal mass. When you try it, I suggest you weigh out the quantity of material and time it to complete melt. Keep in mind that a second or third melt will go faster since the furnace is already up to temp.


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## Larry$ (Jun 21, 2022)

I've been casting aluminum alloys using propane in a home-built furnace someone else made. Steel angle iron frame Large hard "brick shell, soft insulating firebrick lining. Lid is a steel frame with the firebricks suspended by putting grooves in them to keep the steel away from direct heat. It works but has the usual disadvantages of fuel fire for aluminum and trying to control the amount of hydrogen bubbles. I've bought commercially available compounds that are supposed to help with the hydrogen.  I'm now convinced to build an electric furnace. 

The furnace lacks sufficient insulation to get to melting copper. In the past I helped my sister build a ceramic kiln. 55 gallon drum lined with 2" of  Kaowool, fired on propane. We could hit cone 9, 2300°F.


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## Firstram (Jun 21, 2022)

Larry$ said:


> I've been casting aluminum alloys using propane in a home-built furnace someone else made. Steel angle iron frame Large hard "brick shell, soft insulating firebrick lining. Lid is a steel frame with the firebricks suspended by putting grooves in them to keep the steel away from direct heat. It works but has the usual disadvantages of fuel fire for aluminum and trying to control the amount of hydrogen bubbles. I've bought commercially available compounds that are supposed to help with the hydrogen.  I'm now convinced to build an electric furnace.
> 
> The furnace lacks sufficient insulation to get to melting copper. In the past I helped my sister build a ceramic kiln. 55 gallon drum lined with 2" of  Kaowool, fired on propane. We could hit cone 9, 2300°F.


What's cone 9?


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## Larry$ (Jun 21, 2022)

Firstram said:


> What's cone 9?


When firing ceramics, it refers to the temperature that you heat the kiln to. In this case 2300°F. The cones are small ceramic "cones" that bend over when the temperature is reached. If you are using a cone setter, a mechanical finger rests on the cone. When the cone deforms enough the finger trips a switch and turns off the kiln. Ceramic kilns usually use a controller that steps the temperature up & down to prevent thermal shocks and breakage. It also ensures the ceramic has had time to reach vitrification all the way through. I think cone 9 fired ceramic is usually thought of as porcelain.


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## Firstram (Jun 21, 2022)

Single use mechanical PID! Learn something new every day.


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## MrCrankyface (Jun 23, 2022)

Somehow even a simple thing like a hinge can get out of hand.
Functionally it can lift the lid and then rotate it out of the way.
Added a little extension to the lid, both for looks and to lessen twisting force on the joint between handle and lid.
Finished welding it and then blending everything, literally hours of work just there. 
Quick mockup roughly how it's going to sit.



Aaand lots of hours here as well somehow.
Square tube was just drilling some holes, fast.
Bottom left was a 40mm hot rolled bar, milled flats so it'd fit in the square tube, cleaned everything up and bored it out for the shaft on the right.
Also added the little "roofwasher" from some other junkpiece.
Couple of hours getting all that done and the fits right.
Bottom right piece was a 60mm chunk of alu bar and 25mm steel rod. "Lathed" and polished part of the steel rod to fit in the left piece.
Squared up the alu piece, bored it out for a pressfit for the steel rod and then some hours in the mill, making the shape up as I went.
I'm pretty bad at "making things up as I go" so I'm trying to get more practice doing that, instead of spending hours in 3D-CAD.


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## MrCrankyface (Jul 1, 2022)

Back at it again, been crazy warm here lately so mostly been laying still.
Spent 2 hours on the lathe to make this purely decorative piece.
Would've been faster on the mill but I wanted to try some techniques out.



Cut the tube/handle down to length and beveled it off.
Whilst a long straight handle would give more leverage, I find it unneccessary and a trip-hazard.



So after some more welding, blending and adjusting.
Lid gets angled up and can then be rotated to the side and let down again.
Will incorporate both "lid open" switch for the coils and physical endstops so the movement is a bit constrained as it can now rotate 360*.


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## rwm (Jul 2, 2022)

This is looking great! Throw some aluminum in there!
Hey, keep in mind that after a few heatings the coil will start to shorten and may move inward or even fallout of a groove. This is unfortunately normal but something to watch for.


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## mmcmdl (Jul 2, 2022)

Somehow I ended up with 18 150ml cricibles all packed up in a box . My brother melts silver and gold and said he'll take a few .


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## matthewsx (Jul 2, 2022)

mmcmdl said:


> Somehow I ended up with 18 150ml cricibles all packed up in a box . My brother melts silver and gold and said he'll take a few .


I'd like a few of those too.


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## mmcmdl (Jul 2, 2022)

matthewsx said:


> I'd like a few of those too.


I'll get a pic of what these are before they get lost in the shuffle .


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## MrCrankyface (Jul 2, 2022)

rwm said:


> This is looking great! Throw some aluminum in there!
> Hey, keep in mind that after a few heatings the coil will start to shorten and may move inward or even fallout of a groove. This is unfortunately normal but something to watch for.


Thanks! I'm hoping the "outwards lean" of the coil slots will help counter this, but I'll monitor the situation! 

Getting real close to "starting" this thing for real.
Milled out two slots underneath the hinge piece.
One acts against the shiny bolthead as a physical stop and the smaller pocket/slot acts against hole where you can barely see the end of a microswitch sticking up, this will make sure the coils turn off if you open the furnace.



Spent a ridiculous amount of time on this control box.
Bought a "premade" fusebox figuring it'd save me time but ended up having to modify it internally.
Being plastic I also wanted to protect it both from physical damage and from radiating heat, hence the aluminium sheet cover.
Behind that is some folded up steel sheet to distance it from the furnace itself.



Nothing is wired up yet, waiting for some 3D-prints to hold the PID controller and I also need to source both something insulating to wrap the kanthal wires in, and also ceramic/hightemp connectors so I can connect my silicone wires to the kanthal.
Both of those are seemingly hard to find here..



mmcmdl:​Must be real small and cute! The smallest crucible I have is one of those 1kg graphite ones, I think it's roughly 300ml and I thought that was relatively tiny when I got it.


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## mmcmdl (Jul 2, 2022)

MrCrankyface said:


> Must be real small and cute! The smallest crucible I have is one of those 1kg graphite ones, I think it's roughly 300ml and I thought that was relatively tiny when I got it.


These are small ! CoorsTek wide form 150 ml cups . Couldn't even make it as coffee cups around here !


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## mmcmdl (Jul 2, 2022)

CoorsTek 60139 18 pack .  Says they're porcelin 150 mls .


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## MrCrankyface (Jul 9, 2022)

Alright so a little progress again.
Bent up a bunch of stainless wire, hoping this will reinforce the cement.



To get a decent seal against the bucket I decided to put the lid in place and fill from the top.
Put an old headlight in place and sealed everything up.



Felt a bit unsure about this since the hole is quite small and it was difficult to push the perlitecement in.



And as I feared, didn't manage to distribute and pack very well along the bottom.
Should probably have tried vibrating it to shake things into place.



Decided to cover it with a layer of high-temp cement, hopefully it binds well to the previous cement and protects it a bit.
Once this has set properly I think it's actually finally ready for some heat!



Also made a brick with some leftovers, same thing here that it seems hard to pack it and distribute the cement. 
Will have to try vibrating it if I do it again.
Will still be useful to test how it reacts to fire and heat.


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## rwm (Jul 11, 2022)

The lid looks fine. That will work just fine. 
The PID controller is probably overkill. These electrics take so long to melt Al that you pretty much just melt it, skim it, and pour. It may be useful if you decide to do heat treating or something like that.


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## MrCrankyface (Jul 17, 2022)

PID is definitely overkill, a simple on/off controller would've been good enough but comically are harder to find cheap than PID.
I want to try case hardening sometime in the future so some kind of temp control is definitely needed.

Finally got it all up and running.
Gradually increasing temperatures over time. Initially it was cooking off a lot of steam even at 100c, as it calms down I would increase the temp further.
As the temperature started creeping out into the insulation I'd notice both the bucket and lid start sweating and steaming more so takes quite some time to dry it out.



After several heatcycles I decided to go all the way up to 950c and try melting silver.
While waiting for it to heat up I started making a mold.
Didn't have enough sand so the top is only half-full, making it very delicate and at risk of falling out.




Pour itself went pretty good but definitely scary doing it for the first time.
Managed to touch the wood frame with the red-hot crucible causing both smoke and a bit of flame.
Definitely a challenge both aiming and keeping a consistent pour rate.



End results with silver.
Took a bit of cleanup and I definitely need to get better at mold making as a lot of the edges were damaged when I tried to get the pattern out.
Looking forward to doing some more casting stuff but with aluminium instead.


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## rwm (Jul 17, 2022)

Outstanding! Love to see this. 
I see you are not fooling around; starting out with Ag! That is almost brass temp. 
You will get used to burning your flasks. All mine are charred. If you get really into casting you can cast your own flasks in aluminum but wood works just fine.


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## Larry$ (Jul 18, 2022)

A good first pour. Sometimes I turn scrap metal into scrap metal. My first attempts at making cores were less than ideal. 
Always wear your safety gear, dropping a crucible full of molten metal would not be good. 
Do you ever watch Windy Hill Foundry videos? Olfoundryman videos are excellent.


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