[Bob] needed an oven for powder coating metal parts. Commercial ovens can cost thousands of dollars, which [Bob] didn’t have. He did have an rusty old file cabinet though. And thus, a plan was born. The file cabinet’s steel shell would make a perfect oven body. He just had to remove all the drawers, sliders, and anything combustible. A few minutes with an angle grinder made quick work of the sheet metal. The drawer fronts we re-attached with hinges, allowing the newly fashioned door to swing out-of-the-way while parts are loaded into the oven.
The oven’s heating elements are two converted electric space heaters. The heating elements can be individually switched off to vary power to the oven. When all the elements are running, the oven pulls around 2000 watts, though full power is only used for pre-heating.
[Bob] used a lot of pop rivets in while building this oven, and plenty of them went into attaching sheet metal guards to protect the outside of the heating units. To complete the electrical equipment, a small fan was placed on top of the oven to circulate the air inside.
The most important part of the build was insulation. The entire inside of the oven was coated with aluminum foil and sealed with heat proof aluminum tape. On top of that went two layers of fiberglass matting. Metal strips kept the fiberglass in place, and the stays were held down with rivets. One last layer of aluminum foil was laid down on top of the fiberglass. Curing powder coating produces some nasty gasses, so [Bob] sealed the gaps of the oven with rolled fiberglass matting covered by aluminum foil and tape.
[Bob] was a bit worried about the outside of the oven getting hot enough to start a fire. There were no such problems though. The fiberglass matting makes for an extremely good insulator. So good that the oven goes from room temperature to 400 °F in just 5 minutes. After an hour of operation, the oven skin is just warm to the touch.
If you need to find [Bob], he’ll be out in his workshop – cooking up some fresh powder coated parts.
VERY nicely done hack. I probably would have sprung another $50 for a digital temp control, but for your budget, great job!
$15 PID off eBay works just fine.
Very nicely done, but wouldn’t a second-hand kitchen oven do (yes, I realize it wouldn’t look as cool, work as well or be as much fun to do)?
Would probably work just as well. Heating elements and insulation are already inside and some even have fans. Most have a convenient view port too.
I wonder how much more efficient it would be with some fans and moving the heater to the bottom.
Normal kitchen ovens take a lot longer to preheat and vent carcinogenic air to the environment while heating powder coating. Sealed ovens are usually far more efficient.
Powder coat is very low VOC. Any fumes vented are not carcinogenic.
I’ve got a pizza/toaster oven, a kitchen oven, and a fridge. Well, the shell of a fridge.
Two points: insulation really isn’t all that important (you don’t need much), and don’t put the heaters on the side like that (on the bottom is easier and works better).
And yeah, get a PID (most oven controllers are rubbish).
I’d be worried about things dripping on the elements if they were at the bottom.
I haven’t tried powder coating before. With powder coating, does it have to be heated in an oxidizing atmosphere or can you use propane or natural gas? (Reducing atmosphere)
Powder coat doesn’t drip when it cured (well, it can, but if it does you’ve put it on too thick).
People with huge oven use propane, you can only get so much heat from the power lines. Generally frowned upon for small ovens (fiddly, gas & powder explosions and all that).
I guess they’d use some sort of heat exchanger as the byproducts from the gas burning would contaminate the part. And by heat exchanger, simply a box in the bottom of the oven where the gas burns, heat radiates through the top.
Those look like halogen/infrared heaters. They work much better when they can actually radiate onto the object to be heated don’t they? Not really suitable for space heaters.
They mention on the website that they are specifically ceramic (the old type) and not halogen. Halogen only warms what it hits and not the air. That’s not really suitable for powder coating.
If 2KW goes in, it’s gonna come out somewhere. Heaters are heaters, by definition they can’t be much less than 100% efficient.
You’d get uneven heating with one heater stuck on the side like that. You’ll get weird convection patterns as well, but eh, it’ll work.
A small air vent helps with air flow, they mentioned they didn’t add a vent as the fumes coming off powder coat are carcinogenic. That’s not true; powder coat is very low fume because it doesn’t have any solvents. Maybe they need to read the MSDS. The only danger from powder coat is a box of it falling on you.
If the heaters were on the bottom, they would be blinded out with powder dust in no time at all. If you read the text, it says they have a slow fan at the top. I assume that is the black boc on the top. The main site has extra photos which shows a fan too.
For powder coating, 2kW of energy might go in, but it needs to be evenly distributed through the air and not directly on the object being coated. Oherwise you end up with hotspots during curing. No emergency, but not ideal.
If powder is falling off your parts in the oven, you’re doing it wrong.
(You don’t spray powder in the oven, you have a spray booth for that)
(For “spray booth”, a large cardboard box works fine)
You’re right, they do have a fan. But putting an element on the side next to the part is still a fail, that’s a huge hot spot there.
Yes a kitchen oven works fine but restricts the size of an object you can put in, one is currently being used at the Milwaukee makerspace
I got a couple rattle cans of spray paint. Good enough.
If spray paint is a good enough powder coating substitute for you, then why do you complain on nearly every project posted that there are better options?
I thought I just did. For me spray painting is a better option. Fail harder next time.
“For me spray painting is a better option.”
if you want your project to look like a used trash barrel, good on you
If I painted a trash barrel it’d be beautiful. I’ve just done a lot of painting up to now. In the course of my life I’ve got to admit, I’ve gotten pretty good at it by now too. In fact I can do things today that I used to think were impossible. Stuff like say getting a glass gloss clear finish with a brush on wood.
But you said ‘Good enough.’ Good enough is not better. It is adequate, marginal, sufficient, nearly as good, that is: a substitute. Your later response is not just a non sequitur, it is a blatant contradiction. Then you attempted to offend afterwards.
Why do this? How do you benefit? If it is to bring other people down or to troll, wouldn’t a larger audience make you happier or more satisfied? Reddit and youtube and facebook and all of those other places would be a better option. If it is in a genuine desire to improve projects, then why do you not use rationalism or substantiate any of your claims? Being actively hostile will merely galvanize people against what you say, thus the more emotional energy you put into your words, the less likely people will be receptive of them.
As it is now, your behavior is not of significant benefit to you. It fails to provide positive external change and it fails to deliver a significant volume of negative responses.
Actually I can paint better than a powder coat finish, if I want to. Maybe you can’t, but I can. Oh you want proof do you? Let me find a picture of my car I spray painted.
http://a.imageshack.us/img832/1705/p1010023w.jpg
It is a bit worse for the wear and tear today, but I painted it 20 years ago. Considering that I think it is holding up pretty good.
So suck it.
Baaaaaa.
Hit it with a hammer and see what happens to your paint. Or http://www.youtube.com/watch?v=_D8TnpcMZe8.
I’ve even powder coated springs.
Suck on that, you woolly-brained moron.
is aluminium foil a goot insulator? I can understand it stopping air from escaping, but not a lot else… will have to go look it up.
There’s a wall of fiberglass insulation between the walls of the cabinet and the aluminum sheets.
Looks like the foil is actually over a layer (or two) of fiberglass matting underneath which is what probably does a lot of the insulating.
Aluminium foil is not a good insulator, but it *is* a good reflector, so most of the heat goes back to the oven rather than hitting the insulator.
I’ve heard white paint is an even better reflector than aluminum foil is. Least that’s what the indoor pot growers tell me.
Most fFibreglass insulation is usually only rated around 300C (powder coat need 200C). Even at lower temperatures it goes brittle and breaks down.
Rockwool is rated to high temps.
Kaowool is rated for high temperatures. Rockwool is distilled evil!
Kaowool, Rockwool and mineral wool can all cause Silicosis of the lung. I’m not a safety queen, but I wear a respirator (not just a mask) when handling any of those.
Kaowool doesn’t irritate your skin? It makes me extremely uncomfortable if I get it on me. I only ever get to play with it when it is old though, and we’re tearing it out of places. I’m convinced that it gets brittle with age, and breaks up more easily then.
In the source article, they are talking about fibreglass matting, not spongy fibreglass wool. I would think the wool type would squash down over time, but not the matting. And yes, at less than $50, strip it all out every couple of years if you have to. It beats paying $5000 for an oven!
Wool or matted, it’s still fibreglass. The max temperature isn’t all that high, but it’ll work for powder coating.
Ovens aren’t rocket science, they’re a metal box with a heater.
$5,000 sounds about right for a new one, but 2nd hand ovens are cheap. Cheaper than DIY at times. Especially when you realise that that powder coating / bakers / paint / etc ovens are all the same thing. (A kiln is something else).
Wait until someone renovates and grab their kitchen oven.
I dont really see the interior holding up, especially with aluminum foil. Plus the insulation is at most, 1/2″ thick, maybe. For $50? not bad, but I know that even with the small amount of powder coating I do that it wouldnt last.
“but I know that even with the small amount of powder coating I do that it wouldnt last.”
How do you know? Testing that theory would be a fun project.
Aluminum melts at 1,220F. I do not think this rig gets quite that hot. Folks wrap stuff up in aluminum foil regularly and pop it into an oven you know?
Looks pretty nice. I’ve thought about buying powder coat equipment in the past, but for the space it takes, I just have someone else do it.
I’m surprised someone mentioned spray painting. I wonder if they’ve ever paid attention to the difference between paint and powder coating. Yeah, rattle can will get color on.
pcf11 is a well-known moron here.
Powder coating beats paint – especially shitty spray cans – hands down.
Powder: clean, spray, cure. 30 minute turnaround, no clean up, perfect result.
Paint: clean, primer, clean up, wait, sand, clean, paint, clean up, wait, sand, clean paint, clean up, wait, sand, clean, top coat, clean up, wait.
Oh you’ve hurt me so much with your comment. Actually if you had any brains you’d realize how much you’ve hurt yourself. But we don’t have to worry about that, now do we Tony?
Baaaaaa.
you two should really just get a room.
The one pcf11 is in has rather nice padding on the walls.
Damn, very nice! Seems kind of like a waste of a file cabinet though, they’re the kind of thing that are sort of a pain in the ass to buy new.
I’d been thinking about building a powder coating oven from scratch not that long ago– until now I’ve only been able to toasterize (haha) smallish parts in a Black & Decker InfraWave oven –by just making a big box out of sheet metal, and lining it with panels of stonewool insulation. Seems like it shouldn’t be too hard of a design to engineer, and you can make it whatever size you want. Sheet metal, insulation, some $20 infrared toaster ovens (Or space heaters, wherever you get your elements from), a PID, and a bunch of pop-rivets.
can someone please call the fireman?
Something I forgot about…
If you are going to DIY your oven, you really need a window in it (use the glass from an old oven door).
The reason is you (typically) bake powder for 10 minutes to cure it, however the time doesn’t start until the powder starts to melt (flow out).
Even with small thin items it can take a couple of minutes, and of course if you open the door to check you lose temperature. Just because the sensor in the oven says it’s at 200C, that doesn’t mean the part is.
Typically I hire or visit the Etch Coatings Company to do the powder coating on my stuffs but I think I need to try DIY for small stuffs like an oven.
What is pcf11going on about if that car was powder coated the finish would still be as good as the day it was done. I have only seen powder coating done with a negative iron spray gun if that is the right name for it and the finish is fantastic and with paint a little scratch and the rust spreads but with powder coating it does not so I know what I would use.
Wow! I would never think of turning an old filing cabinet into an oven. I think it is brilliant you lined the inside with aluminum foil. Do you have to replace the foil often or is it pretty durable for your purposes? I want to try to make a smaller oven out of a 2-drawer filing cabinet. Do you think I would have enough space to attach all of the parts?
Great idea!!! What is a PID????
Water heater blanket on the outside of the cabinet, if you want to put foil inside, whatever but it’s not really going to make a difference so long as it’s all sealed well. Much easier to insulate on the outside of something like this vs the inside. I have a and old paint cabinet used for a compressor shed, protects it from weather and is super quiet. Used a 2 door filing cab for the basis of a blasting cabinet, Roomy!
Amazing that you (Bob) were able to build that oven so cheaply. Are you using a PID controller for the space heaters?
This article goes very in-depth on building a large powder coating oven. While the oven is a little more “permanent”, the material costs are nowhere near that of the filecabinet oven build. Oven in question: http://www.powdercoatguide.com/2014/09/how-to-build-powder-coating-oven.html