Marks Kiln build

[dnalot]

I am setting up a bench-top foundry in my shop for doing lost “resin/pla/wax” casting and I need a small kiln. I looked at commercially available units and found the prices quite sobering and then the shipping costs and for me (10.3 percent) sales tax. So I looked at home built units on You-Tube and then decided on building my own. The unit I will be building will be 9” by 9” by 9” on the inside. That can accommodate several casting flasks at once. I expect it will cost about $600 (including shipping and taxes) to build or about a third of the price of a store bought unit. The oven will also come in handy for heat treating metal and doing ceramics.

I have no experience with kilns, so I spent several days at the University of YouTube learning how to go about building a small kiln for use as a burnout furnace.

So it begins with welding up the steel frame work. Not much to be said here except everything needs to be very square or you will have problems later. I bought my steel locally but everything else for the build I ordered on Amazon.

Mark T

 

[dnalot]

It is now time to make the element. I need to make it now so I will know how big to make the cuts in the bricks where the element will sit.

I am using 18 gauge Kanthel resistance wire to make my element from. Here is everything you need to know about this wire.

Kanthal Wire

Specifications: I used this handy calculator to figure out what I needed.

Helpful Coil Calculator Tool for Resistance

The veg oil guy that provided the calculator also has several good you-tube videos on making a kiln.

Using the calculator I gave these criteria 220 volt, 15 amp (my cord and outlet are rated for 20 amps), Resistance of wire .515 and the diameter of the rod I will be wrapping the wire around to make the Coil Element .375”. The wire coil expands a little when released from the mandrel. My outside diameter ended up at .48” That will fit nicly in a .5” grove cut by a router bit with a rounded end.

The calculator gave these results. 3,300 Watts ~ 14.67 Ohms ~ 28.48 feet of wire required ~ 290 turns on coil.

I used my old Atlas for turning the coil because I can turn very slowly with this lathe thanks to the variable speed treadmill motor upgrade. A simple wood block with a slit cut at one end, and mounted in the tool holder allowed me to set the tension on the wire for uniform results.

Here is a link to my lathe upgrade

Variable speed for my Atlas 10" Lathe

All materials will be rated for 2500 degrees F or higher. My thermocouple tops out at 2372 F. So say 2200 F. usable. That is way higher than I will need for my purposes so I will have a healthy reserve and not risk stressing the furnace.

Mark T

 

[Tug40]

Very tidy fabrication.

 

[dnalot]

Very tidy fabrication.

Thanks Tug40, I like to be tidy. But my shop doesn't reflect that.

 

[Richard Hed]

Thanks Tug40, I like to be tidy. But my shop doesn't reflect that.

LIAR! I've been to your shop--it is VERY tidy. I'm surpized that you and Tug have not gotten together to swap lies, since you live so incredibly close to each other. Get snowed in this year?

 

[dnalot]

Get snowed in this year?

Yes Richard, about 15 inches accumulated so far and more coming today. Snow plow stops about two miles from my driveway so have stayed home the last week. Woodstove keeping the shop cozy but UPS stopped delivering materials for some reason. Warm air and rain coming on Sunday. To be honest, I cleaned up my shop for your visit.

Mark T

 

[Richard Hed]

Yes Richard, about 15 inches accumulated so far and more coming today. Snow plow stops about two miles from my driveway so have stayed home the last week. Woodstove keeping the shop cozy but UPS stopped delivering materials for some reason. Warm air and rain coming on Sunday. To be honest, I cleaned up my shop for your visit.

Mark T

CHEATER CHEATER. If it weren't so so far, I would come by more often then you would have to keep it nice and tidy. LOL. I have about 1/3 of your care package ready. Am working on cleaning up MY shop but can barely get thru it at the time. That mill is taking up all the room. the hed is laying on a pallet which is what is taking up all the extra foot space. Have almost gotten the ways completely cleaned and ready to mount on the turret. This mill has "two" turrets. I lookt and lookt for whatever bridgeport model has two turrets and cannot find one. I found a photo, just ONE photo of a model with two but that is all--no other info. It's not really two turrets, but rather a spacer that actually turns just like the turret, then the turret is mounted on top of that spacer.

In all my years workking with bridgeports, I never noticed if they had this spacer or not, as Me thimpfks that I maybe only adjusted the ram maybe once or twice and NEVER turned the turret at all! As I thimpfks about it, I could see that being able to turn that turret in a shop that has lots of space like yours could be extremely useful for large projects.

We got about 2" of snow. Speakking of the weather, that taiphoon in the Phils, wreaked a lot of havoc on our property in MOalboal. Look up Moalboal, Cebu in the philippines on goggle earf and you can see my place at 9deg56'43"N 123deg23'29"E. It's that white building with the hexagonal top. This particular building is made to be taiphoon proof and apparently proved to be how it was built. Some of the eaves were ript out but the roof apparetnly is fine. Anyway, I will be going out there to inspect and repair what has been damaged in late Feb. One building has had the roof ript off and it's impossible to say how badly it is really damaged. Trees are down all over the place, mangoes do not stand well in taiphoons, lucky none landed on any buildings. The report is that this taiphoon was worse than Yolanda about 5 years ago. I was there at that time, and it wasn't bad in Moalboal, but bad in other placdes. This taiphoon was supposed to be worse--certainly worse in MOalboal.

The electricity is still not back on there and so we do not have a report from our caretakers. A neice, however, managed to send some photos. Unfortunately, she doesn't know how to take good photos!

 

[Randoo]

I bought my steel locally

Hi, Mark. I live in Kelso and would like to know where you buy your steel?

Randy

 

[dnalot]

I live in Kelso and would like to know where you buy your steel?

Online metals in Seattle. I am up that way fairly often and I pick it up there rather than having it shipped. They stock almost everything but shipping is a budget buster.

Mark T

 

[dnalot]

I am using 13 soft fire bricks 2” x 4.5” x 9” in all areas facing the ovens interior. And I will be using some castable refractory cement to make custom shaped boarders that will secure the bricks in place. No grout or other binders are being used as I expect those joints would probably crack from the heat and expansion of the materials. Instead I will be using some keyed joints and a few pins to locate the bricks and the cast parts in place. The galvanized sheet metal shell will hold it all together. I allowed for expansion of the refractory with a 1/2” thermal blanket between the refractory and the sheet metal.

A note on the sheet metal. I used .030” sheet. It forms easily and I was able to form it without a brake.

I used my table saw and a router table to make the cuts in the bricks. If you can do this outdoors do so, it really makes a mess. Its freezing cold here so I did mine in the shop. To help reduce the mess I used a variable speed controller for my router and set it to about 2000 rpm. It took about an hour and a half to make all the cuts and the rest of the day to clean up after.

The bricks are very fragile but they came nicely packaged and none were damaged.

Mark T

 

[Richard Hed]

I am using 13 soft fire bricks 2” x 4.5” x 9” in all areas facing the ovens interior. And I will be using some castable refractory cement to make custom shaped boarders that will secure the bricks in place. No grout or other binders are being used as I expect those joints would probably crack from the heat and expansion of the materials. Instead I will be using some keyed joints and a few pins to locate the bricks and the cast parts in place. The galvanized sheet metal shell will hold it all together. I allowed for expansion of the refractory with a 1/2” thermal blanket between the refractory and the sheet metal.

A note on the sheet metal. I used .030” sheet. It forms easily and I was able to form it without a brake.

I used my table saw and a router table to make the cuts in the bricks. If you can do this outdoors do so, it really makes a mess. Its freezing cold here so I did mine in the shop. To help reduce the mess I used a variable speed controller for my router and set it to about 2000 rpm. It took about an hour and a half to make all the cuts and the rest of the day to clean up after.

The bricks are very fragile but they came nicely packaged and none were damaged.

Mark T

View attachment 132339

View attachment 132340

Did you say where you got the bricks? I want to get some but they are SO INCREDIBLY expensive that I have balked at getting any so far. I need some for various purposes.

 

[dnalot]

Did you say where you got the bricks?

Everything except the steel I bought on Amazon. And yes the bricks are not cheap, it is what it is. They are of excellent quality.

https://www.amazon.com/dp/B081K26JZM?psc=1&ref=ppx_yo2_dt_b_product_details

Mark T

 

[Tug40]

Randoo, i buy steel for my welding projects from Waites in Longview.
Lotsa remnants, & round rems for machining projects.
I’ve been gonna go to Metal Supermarket in Portland, (look up their website) to see what they have, they’re by PDX Costco. Never been there myself yet.
Usta but from Wayron, before they went outa business.

 

[Randoo]

Randoo, i buy steel for my welding projects from Waites in Longview.
Lotsa remnants, & round rems for machining projects.
I’ve been gonna go to Metal Supermarket in Portland, (look up their website) to see what they have, they’re by PDX Costco. Never been there myself yet.
Usta but from Wayron, before they went outa business.

Thanks for the info! You must be near me?

Randy

 

[dnalot]

Randoo, i buy steel for my welding projects from Waites in Longview.
Lotsa remnants, & round rems for machining projects.

I will have to check that out. Rando & Tug40, we should get together for lunch sometime.

Mark T

 

[dnalot]

I started with the kiln floor, casting the horse shoe collar around the two soft bricks that will be the bottom of the kiln's interior. The corners are reinforced with piano wire as I expect to see cracking here. And I cut a notch into the soft bricks to stretch some piano wire across the bricks to hold the ends of the horse shoe brick in place. The castable refractory needs to be fired to come to full strength. Instructions on the bag called for gradually bringing the material to 390 degrees in kitchen oven over several hours.

With that done I used high heat silicon to secure it to the metal frame. The fire bricks set directly on the steel frame and the cast portion of the floor sits about .125” above the frame to allow a thick build up of the high temp silicon to hold the bottom in place and provide flexibility for heat expansion.

Mark T

 

[Richard Hed]

I started with the kiln floor, casting the horse shoe collar around the two soft bricks that will be the bottom of the kiln's interior. The corners are reinforced with piano wire as I expect to see cracking here. And I cut a notch into the soft bricks to stretch some piano wire across the bricks to hold the ends of the horse shoe brick in place. The castable refractory needs to be fired to come to full strength. Instructions on the bag called for gradually bringing the material to 390 degrees in kitchen oven over several hours.

With that done I used high heat silicon to secure it to the metal frame. The fire bricks set directly on the steel frame and the cast portion of the floor sits about .125” above the frame to allow a thick build up of the high temp silicon to hold the bottom in place and provide flexibility for heat expansion.

Mark T


View attachment 132370View attachment 132371

I would recommend putting a strut under that U-shaped brick in this last photo

 

[ddmckee54]

If you are building this as a burnout oven, where's the drain? When doing lost wax, MOST of the wax can actually be caught and recovered/reused. I'm not sure about lost PLA or lost resin, but I would think that you'd get something slumping out of the mold. With no drain it looks like yours will be a total loss system, everything will have to turn into smoke and ash? As is, this WILL make a dandy heat treat oven though.

Don

OK, I just realized that you could actually put the molds over a catch pan in the oven, then ramp your temperature up to the melting point and hold. After a long enough time to melt out the material, remove the pan and then continue with the burn-out cycle. (Didn't QUITE have brain completely engaged.)

 

[dnalot]

I would recommend putting a strut under that U-shaped brick in this last photo

The cast U shape is supported by cross bars and is held in place by hi temp silicon

Mark T

 

[Richard Hed]

The cast U shape is supported by 4 cross bars and is held in place by hi temp silicon

Mark T

Naturally, I can't see what is under that, but it doesn't look like it is supported except on the edges. Does the hi temp silicon stop it from sagging?