Heater elements

[andrewg1323]

Basically i'm looking to build a coupla things that need heating elements and not sure what to use!
1) An oven for curing powder coated items
2) A Vacuum plastic former

Been looking at vids of the plastic formers on youtube and figure i can just do what a few people on there have done and build the case out of fireproof plasterboard which should be ok. figure i can do the same for the outer walls of the oven (that way i can make it any size i need) but not sure what to use heater element wise?
Electical appliance elements? Ovens, washing machines etc?
Anyone got any advice or guidance? i'd ideally not wanna kill myself this year!

 

[rtbcomp]

Why don't you just use an oven? Fan ovens can be got for free from Freecycle.org. They tend not to have a timer, but one can be got from a scrap basic microwave.

If you want an element go for an oven element or tumble drier element, these are designed to be used in air, whereas washing machine elements should be submerged.

Also you can get thermal cutouts from the oven or tumble drier that you scrap.

 

[Ratty]

I can't help on the element side (other than suggest you check out RS components) but for the casing of the oven - fireproof plasterboard? - I have no experience but I'd imagine it just has some impregnation to the surface to stop it catching fire, it may not stand up to constant high temperatures. I would consider making it double skin with a steel inner and use ceramic blanket in the gap. I have an old gallenkamp vac oven (one of my better skip finds) which is a 5mm steel drum with 3" walls and the outer casing is plastic. I'm sure you could get away with thinner steel or you might be able to get some sort of steel container/drum/tank from a scrappy that you could adapt. You need to conduct the heat into the oven, plasterboard would actually insulate and keep the heat within the walls. Ceramic blanket is fantastically heat proof and is used in furnaces & kilns. The outer walls could be made in ply or MDF or just ordinary plasterboard as there should be no heat there (if there is then it's going to waste and you need more blanket!).

 

[Alex]

I used to do some vacuum forming years ago,

Its very possible to make a basic unit with MDF and some time with the cordless drill, thats the easy part.

You can get some limited success with the Record power 1KW tool vacuum, but you wont be able to do intricate forming.

Its also very possible to make up a heating element with steel frame welded or bolted together. I would look at using an old grill element connected direct to your switch or contactor.

 

[andrewg1323]

Cool gives me some ideas!
Main reason i'm not using n overn is i will eventually want to powdercoat stuff far too big for an oven so cant go that route unfortunately!

 

[Lippyp]

If you want a really big one then why not build it from firebricks? Add a load of insulation behind them and another skin of maybe thermalite blocks and it should keep the heat in nicely. You're going to need a fairly hefty power supply though to get a big oven hot and keep it hot with no cold spots.

 

[rtbcomp]

If you want a really big one then why not build it from firebricks? Add a load of insulation behind them and another skin of maybe thermalite blocks and it should keep the heat in nicely. You're going to need a fairly hefty power supply though to get a big oven hot and keep it hot with no cold spots.

You can get suitable bricks and elements from old night storage heaters.

 

[pennytrucker]

Have you seen-



http://machinebuilders.net/plans/gallery/Big Kids/PowerCoat Oven1.pdf

 

[rtbcomp]

That first link brought up ads for a drive cleaner, error checker, registry tools and the pics didn't load. Maybe as well to be wary!

The second one was OK though

 

[Alex]

If its in your home I dont think you'll be able to get enough energy from the electrical supply to your home.

I think you will need to heat the 'oven room' with gas or 'coke' (coal). If you use fans you should get a fairly even heat throughout.


Good luck its a big job to do properly.

 

[Moseph]

Propane gas has an enormously high calorific value. If you get the setup right, it will also yield almost 2000c - not that you'll need a temperature that high!

 

[rtbcomp]

The power consumption shouldn't be a problem if you insulate the box well. Even a 3kW element will attain a high enough temperature if the heat doesn't escape, it will take longer to heat up though.

Do you have to put the item to be coated into a pre-heated oven?

 

[andrewg1323]

I like that link with the powdercoat oven might have to make me one of them!
IIRC the powdercoat needs 10 mins in an oven at 200 centigrade cant see why i cant heat it up with the item already inside though

 

[Alex]

I'm assuming this is a walk in type oven?

like the size of a medium size shed?

 

[andrewg1323]

Nah i'm thinking biggest i'll want to do is crossmembers etc. so max about 70 inches long by a foot width and height

 

[Alex]

In that case go electric it will be easier to control temps and probably cheaper.

 

[Moseph]

I was under the impression you were after something in excess of 2M x 2M x 2M!!! Gas would probably be unnecessarily powerful!

 

[andrewg1323]

Had a bit of a result today, went too the bodyshop where they were dismantling an old catering hotplate trolley to use it as a regular stainless bench for mixing paint on so i;ve come home today with 3 one foot square heating elements plus the thermostatic control all wired to a plug ready to roll!

 

[Alex]

Sounds good.

Maybe you could tell me a bit more about powder coating, i'm quite interested by its robustness compared to paint.

 

[andrewg1323]

What you need to know?
Basically you in effect spray on the powder and electorstatically charge it at the same time to help it stick to the metal
i.e. you have an earth clamp on the item to be powdercoated like in welding and the guns positively charged on a foot pedal (might be other way around cant remember!) and the powders stuck surprisingly well once its all done even before curing