Heating oven - Electric..

[NeoTech]

So this is a start for a small electric oven / kiln..

I have 3, 5kW heating elements and a pid, k-sensor and a 3 phase relay from ebay lying somewhere i will be using for this..

The frame is just welded up from 20x20x3 steel profiles, And the bricks is the standard fireproof 25mm thick fireplace bricks you find in the woodstore.. They are rated for 1380C.. and i aim to run this oven to max of 900C.. Its main purpose will be heating steel for quenching in a safer manner than i used to do it.

Im gonna try to find some superwool or kaowool for the inside of it or i will just go with rockwool on the outside of it (not the best choice but it works kinda good actually. Best if a kaowool lining could be put in place and rockwool on the outside as well.. That would probably be the best combination of insulation.

Anyway, images..

[awemawson]

Slight problem with the drop down door design: You will be reaching over a door that will roast you from the radiated heat. Side hung it can swing out of range of cooking you.

[NeoTech]

Ah well thats true, problem with sidehung doors is that they tend to "close" on you if you are carelss and you will get burned..

Most commercial electric kilns actually come with a dropdown door like that.. So i mostly stole it from someone else.. If its really annoying i will consider redo it.. For know its pretty well welded there. ;D

Having issues finding insulation blanket that doesnt cost me my first born child..

[bhowden]

I was lucky and my neighbor once had a business building pet crematoriums for animal hospitals and had a bunch of high temp wool he gave me when he retired.  What are you using for elements and where did you get them?  Stove elements look perfect from a cost, availability, form factor, safety etc. point of view but they won't stand the high temp.   I once tried making a self contained direct contact aluminum casting crucible.  I wrapped stove oven elements directly around a steel crucible and bonded a stove top element to the bottom then wrapped the whole works in insulation and a sheet metal outside.  The idea was to quickly heat the crucible with direct contact heat and then lift and pour the whole works so I didn't have to manipulate the crucible out of the oven.  It worked great but the elements had a very short life span.  I probably could have done better if I embedded thermocouples in the mix but I think the best answer would have been higher temp elements.  I ended up buying a used pottery kiln which works but takes much longer to heat up and I still have the extra handling when I do a pour.  The elements on a kiln are exposed and live so unsuitable for wrapping around a steel crucible.

Brian

[NeoTech]

I will be using 5kW kiln elements of this type

http://www.ebay.co.uk/itm/3KW-Kiln-Furnace-Kanthal-A1-Heating-Element-Coil-Heater-Wire-790mmx5-5mm-/121145447486?pt=LH_DefaultDomain_3&hash=item1c34d4d43e 

( yes thats a 3kW but i didnt find the ones i bought )

[tom osselton]

I just made a furnace and got all I needed from a ceramic supply store  the insulating fiber was $12.60 a foot by about 3 foot wide they also have the element wire there thats your best bet.

[NeoTech]

Ah well.. i live in sweden, the country that despises private customers.. So i need to look elsewhere.. ;(

[bhowden]

I will be using 5kW kiln elements of this type

http://www.ebay.co.uk/itm/3KW-Kiln-Furnace-Kanthal-A1-Heating-Element-Coil-Heater-Wire-790mmx5-5mm-/121145447486?pt=LH_DefaultDomain_3&hash=item1c34d4d43e 

( yes thats a 3kW but i didnt find the ones i bought )

Wow, the price is right!  Unfortunately that is the exposed element similar to what I have in my kiln.  It is electrically hot so you want to make sure it is off when you open the oven.  I am still looking for a source of high temperature insulated elements similar to the element in a domestic oven only rated for higher temperature.

Brian

[NeoTech]

Well you can dip it in a zirconium paint or silica based paint..  But yeah your right, you need to make it turned off.. i plan to install "off" switch on the lid..

[tom osselton]

Iv'e been looking at this place  http://www.graphitestore.com/index.asp

You could also for your door have it pull towards you and swing down keepng the heat away from you.