Foundry furnace

[Tomc938]

Anyone have any experience using a pottery kiln as the basis for a furnace? I have a line on one cheap. Was thinking to convert it to propane/ used oil fired. I’m thinking it would have decent insulation value - better than the 5 gallon pail I currently use. Any thoughts would be appreciated.

 

[DavidR8]

The sum total of my experience comes from watching many hours of foundry videos so take this with the commensurate grain of salt.
I think the large interior volume would necessitate a very large burner along with associated fuel costs.
Mark Presling built a very nice propane powered furnace from an empty 20lb propane tank and recently converted to diesel because of the high cost of using propane.

 

[Tom O]

I have a beer keg that is lined with Kaowool (with the C-100 coating) . It uses a blower I had on hand and have never complained about the propane consumption it heats up fast, all the other people I see on the web complaining about the cost have a rammed castable refractory that takes time to heat up I’ve done alu & brass with no problems using a #6 crucible with plenty spare space for bigger crucibles I haven’t tried iron yet but it’s coming. As far as the kiln goes I would use it for annealing, heat treating, ramping the heat to remove crucible moisture after winter storage.

 

[jcdammeyer]

I have a pottery kiln I'm upgrading to micro-processor controlled so I can ramp up and hold temperatures. It's on the project list. Not sure what project number. The plan is to use it for possibly burning out lost wax or pla for casting using my Gingery Gas Fired blown furnace. I have all the bits and pieces. Just haven't gotten around to the finally assembly of all the electronics into a box. And I'd rather use it in the winter than in the summer when outside ambient temperature is 26C.

My foundry has the higher temperature refractory which is designed to be able to handle iron casting. I've only done bronze in it. Being higher temperature means it also takes longer to warm up as it doesn't insulate as well. On the other hand it's not as fragile as the softer more porous better insulating type.

Back when I was using propane it cost about $1 to $2 per 6 lb melt running for 20 minutes to pouring temperature. Now that it's on Natural Gas I don't know the actual cost but I figured out once it's about 250K BTU energy usage and runs about the same length of time to melt 6 lbs.

 

[Tomc938]

I asked a follow up question about the kiln.

The kiln is 34 inches high….. inside 30 inch depth….. 34 inches across on the outside….. diameter 10.82 inches inside.

Maybe a false bottom/cut some off the top? I usually use about a 6" crucible, but have a pair of 20# crucibles, lifting and pouring tongs, and the 10.82 diameter would fit them perfectly. (for when I get REALLY ambitious in my casting)

It is almost free, so. I think I'll take the plunge.

 

[trevj]

I asked a follow up question about the kiln.

The kiln is 34 inches high….. inside 30 inch depth….. 34 inches across on the outside….. diameter 10.82 inches inside.

Maybe a false bottom/cut some off the top? I usually use about a 6" crucible, but have a pair of 20# crucibles, lifting and pouring tongs, and the 10.82 diameter would fit them perfectly. (for when I get REALLY ambitious in my casting)

It is almost free, so. I think I'll take the plunge.

My experience, put a digital controller on it and use it as a heat treat oven for large parts, and for cooking the really large turkey you get on sale. Or for cooking high temperature pizzas.

Otherwise, strip it for the soft firebricks, use those to build the basic foundation of a furnace, go with a layer of ceramic wool and ITC-100 to finish, and you should have a pretty efficient furnace.

You could steal the lift linkage from the gingery Furnace, to avoid having to lift the crucible straight up!

 

[Tom O]

The dream foundry I would like is a little bit different to these styles it has the main body of the furnace on a rail system to raise it to expose the crucible for lifting heavier loads. Loading is still from the top.

 

[trevj]

The dream foundry I would like is a little bit different to these styles it has the main body of the furnace on a rail system to raise it to expose the crucible for lifting heavier loads. Loading is still from the top.

That is pretty much the Gingery layout. Charge preheat and feed on the top of the furnace, the top can swing away for de-gassing or adding inoculant, lift the body up and have full side on access to the crucible so you don't have to deal with waving 20 pounds of molten anything in the vicinity of the gadjoulies!

 

[jcdammeyer]

I'd take the plunge if it's almost free.

This is what I have.

This is just one example of the type of stuff that is out there for controlling kilns.

 

[jcdammeyer]

That is pretty much the Gingery layout. Charge preheat and feed on the top of the furnace, the top can swing away for de-gassing or adding inoculant, lift the body up and have full side on access to the crucible so you don't have to deal with waving 20 pounds of molten anything in the vicinity of the gadjoulies!

I wish it were that simple. The furnace for the Gingery only goes high enough to remove the #6. Or maybe wider pipe crucible. But the up side is you can load from the top and also remove the crucible from the top.

 

[trevj]

I wish it were that simple. The furnace for the Gingery only goes high enough to remove the #6. Or maybe wider pipe crucible. But the up side is you can load from the top and also remove the crucible from the top.

Yeah, but you don't have to copy the dimensions, just steal the idea of the lift and swing away system, for your own use!

 

[Tom O]

My pipe crucible is about 6”x6” x12” square tubing with bolts in opposed corners so I always have a pouring spout.

 

[jcdammeyer]

My pipe crucible is about 6”x6” x12” square tubing with bolts in opposed corners so I always have a pouring spout.

Thats about 275 cu in or 26 lbs at an inch from the top. Pretty heavy.

 

[Tomc938]

Thanks to everyone for the input/wisdom.

Before I could get down to look at it (out of town) someone else snagged it.

Guess I'll stick with my Gingery furnace for a while longer.

 

[jcdammeyer]

My Kiln uses those pyramid cones to limit the temperature. They heat up, bend and then the switch opens and the kiln shuts off. I'm not entirely sure it would get or stay hot enough to melt aluminum. That's why I was busy building the controller. Not only for heat treating but to take stab, in the winter, at melting Al. If I'm going to use electricity to heat the shop it might as well melt something too.

This is the little controller bread boarded with display and there's a knob for the temperature Set Point (SP). I have two SSRs and a little interface circuit for that along with two Type K thermocouples.

 

[Dan Dubeau]

While I want to build a nice big waste oil foundry that can do brass and iron, after using my small electric import one for the past couple years I'd really like to build a bigger electric one too, strictly for larger aluminum pours that are too large for my small one. The ease of simply flipping a switch and pouring is too great to ignore.

Kelly Coffield on youtube has what I consider the holy grail for electric aluminum foundrys. I'd love to have that setup someday. He's also nailed the lost foam process down pretty good for a guy in his garage.

https://www.youtube.com/@kellycoffield533/videos

 

[DavidR8]

While I want to build a nice big waste oil foundry that can do brass and iron, after using my small electric import one for the past couple years I'd really like to build a bigger electric one too, strictly for larger aluminum pours that are too large for my small one. The ease of simply flipping a switch and pouring is too great to ignore.

Kelly Coffield on youtube has what I consider the holy grail for electric aluminum foundrys. I'd love to have that setup someday. He's also nailed the lost foam process down pretty good for a guy in his garage.

https://www.youtube.com/@kellycoffield533/videos

What import furnace do you have?
Holy crap that's some amazing work on Kelly's channel!

 

[Dan Dubeau]

What import furnace do you have?
Holy crap that's some amazing work on Kelly's channel!

https://www.amazon.ca/TOAUTO-Automatic-Graphite-Crucible-Aluminum/dp/B0814HF9DV?th=1

That's the one I have. There are a few more brands selling it now, and you may be able to get it cheaper elsewhere, but it's been reliable for me for the past 3 years. Probably up to 30-40 melts now, I haven't really kept track. My only complaint is that I wish it were bigger. Something twice as big would be even better (especially for scrapping runs). But on the flip side, it's perfect for smaller casting sessions. Proving once again that one needs multiples of all tools in all different sizes.

I've got all the ceramic blanket and refractory to build a bigger propane/waste oil one, I just keep finding better more exciting things to do with my free time.

 

[DavidR8]

https://www.amazon.ca/TOAUTO-Automatic-Graphite-Crucible-Aluminum/dp/B0814HF9DV?th=1

That's the one I have. There are a few more brands selling it now, and you may be able to get it cheaper elsewhere, but it's been reliable for me for the past 3 years. Probably up to 30-40 melts now, I haven't really kept track. My only complaint is that I wish it were bigger. Something twice as big would be even better (especially for scrapping runs). But on the flip side, it's perfect for smaller casting sessions. Proving once again that one needs multiples of all tools in all different sizes.

I've got all the ceramic blanket and refractory to build a bigger propane/waste oil one, I just keep finding better more exciting things to do with my free time.

Thanks Dan, I've been eyeing that unit for making small model engine parts.

 

[Dan Dubeau]

I think it would be perfect for doing most model engine parts aside from bigger flywheels and such. Either by sand, or lost wax/pla/resin methods.