Burn out kiln construction ??

[picclock]

Thought I would make a small (12" cube) burn out kiln (electric) for casting work. I figured up to 900C should be adequate with a programmable Arduino temp controller to ramp and hold the temps at the required levels. May also use it to melt aluminium for small casts.

Anyhow, to construction. I figured getting some castable refractory for the side support walls. The castable will have grooves for the kiln element support. I thought of reinforcing the castable with a single layer of 1cm steel mesh. The upper top  of the side wall would have holes for a steel welded grid (as used in an oven) to keep the spacing correct, and the lower part of the wall ~ 4" from the bottom would have holes for a similar grid to form the lower floor of the kiln. The rear,top and lower shelf will just be ceramic fiber blanket glued to the walls/grid with water glass, and treated with zircon paint. The rest of the insulation will be loose poured perlite. Overall insulation depth around 4".

I may fit small fan stirrer to equalise the temperatures, likely also a thin steel tray to catch any nasty bits if something breaks.

Door will be 1" thick made of thin steel (washing machine case ?) hinged with a 3" protruding plug of ceramic fiber wool.

Main concern is whether the castable (1300C) will be strong enough to support the heating elements and the weight of stuff put into the kiln.

Any comments welcome

Best Regards

picclock

[awemawson]

Has the ebay supply of used kilns dried up? When I was lost wax casting people were begging you to take them away! A bit like piano's - they were no longer fashionable.

I got a three phase one and wired the three elements in parallel - I really should get round to returning it to three phase as I now have it on tap (or socket !)

[picclock]

>>>I got a three phase one and wired the three elements in parallel 

Excellent creative thinking.

The ones I've seen on ebay are all miles away from me - I'm near Bournemouth in Dorset. Also they seem either massively large or far too small. Even tried on Gumtree.

Looks like a fairly easy thing to do. I have most of the stuff except for the castable. After its made it should only be a cube ~20" on a side, and not too heavy. Will hopefully not be too wasteful of electricity either - estimate losses at 700W for 800C kiln temp.

Best Regards

picclock

[Coldrolled]

If you have not already done so, check out Keith Rucker and Myfordboy. Both have made gas and oil fired ones but may help with your construction. There was another video that i came accross but due to lack of omega 3 in my diet, i can not tell you who it was but he did experiment with Ni80 with some good results.
 
If you dont mind, would you please keep us updated on your progress. I am planning on building one over the winter time when i have a little more time.

[picclock]

Hi Coldrolled

The kiln I am making is really just for burnout, but will do aluminium ok. I intend to build a propane fired furnace for working with brass and possibly cast iron but that's another project. I have all the bits except the outer steel case which I will cannibalise from a scrap electric cooker.

The temperature controller is Arduino based and uses a thermocouple sensor, a cheap 4x20 line display and a 328 pro mini. I'm using a relay to control the heating elements (2x1200W from China). The controller is a bit customised because I want to use it for many different things. It has 15 programs with 10 steps in each one to allow for heating/cooling at a controlled rate. The program names and settings are controlled by a jog wheel type switch.

pinning at the moment is (from Arduino source file) :
//Simple process oven controller with programmable times/temps.

// temps read using max6675 and K type thermocouple
// pins are 4 for relay drive, 15,16,17 for rotary encoder switch.
//spi on 11 Mosi, 12 MIso, 13 Clock - for temp chip, A4 A5 for I2c display
//pin 8 i/p interlock switch should isolate mains from elements using hardware when door is opened
// Rotary switch can adjust temperatures and times when pushed in. when out menu selection.

Code freely available when finished with the usual caveats.

Best Regards

picclock

[tom osselton]

Nice.

[picclock]

Well my plan to use an old oven as the casing didn't work out, basically too many unwanted holes and wrong sizes. So I've managed to acquire an old four drawer filing cabinet which I can butcher to size. The oven and cabinet were all free local offerings on gumtree so I don't feel too bad about it.

The oven door will be a plug type so to open it will need to pull straight out then rotate. I think I can do this using the drawer runners from the filing cabinet.

Controller schematic attached, very simple and very low cost.

Best Regards

picclock