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Powder coating

Chris Cramer

Chris Cramer

Super User
Vendor
Premium Member
Does anyone here know of a fairly cheap alternative to heating a larger piece of metal after it is powder coated? I've found a good affordable powder coating gun to purchase, only the projects I intend to use it for would be pretty big for most ovens that are within my budget; as well as IR lamps that are used for heat treatment.
 
The largest project I see myself making now is 3'×3'×2", the most common size is 2'×2.5'×2" but they are bound to get bigger once I start using the plasma table. Every project is made of multiple parts, so if it is possible to weld parts that have been powder coated then the parts could be made to be small enough.
 
Shouldn’t be hard to make one out of sheet metal or you could even gut a fridge and install a oven element.... use 2 fridges welded together for a door on each end.
The temp controller is a easy build.
 
Because the temperatures aren't too high, you can buy a garage sale toaster oven, and use the element from that (way cheaper than buying the wire). You can create a custom 3 foot by 3 foot by 1 foot box from a discarded fridge, and insulate with rockwool - add heating and there you are.
 
I remember something similar came up in discussion on a completely unrelated subject a while back. Something to the effect of: is a horrible, shameful old school 100 watt incandescent light bulb really bad? From the light producing perspective, only 5% of energy is converted to light. But where does the 95% 'wasted' energy go? Heat. On a cold winter day I am burning natural gas in my furnace to create what? Heat. Hmmm so from the light ONLY perspective, low energy LEDS are good. But from the light PLUS heat perspective, maybe the oldies aren't so bad. But I digress...

This wasn't the web site, but it was one like it.
https://www.quora.com/How-much-ener...-temperature-of-an-average-room-by-10-degrees
So I took the sample calculation, verified I got the same answer & scaled it to your hot box. It shows very little heat (like 5 x 100 watt light bulbs worth) will raise ambient air to toasty 200C in no time flat. But like some of the subsequent posts in the link & what I recall of the 'environmental' discussion, its not that simple a calculation. It assumes perfect insulation and only heating the dead air, not the contents like your parts which are dense mass metal.

So maybe another way of guestimating is a kitchen oven. They are about 5 cubic feet ~0.14m3 volume. I've read about 5000 watts capacity, assuming that at highest dial temp which is about 250C. That equates to about 35,000 watts per m3 volume. (Notice way higher than the air only calc for only another 50C temp). I guess that's why there is a big ass electrical plug on the back. I'm not sure what your target temp is, but you can probably proportionately scale it all things equal. Lower watts might be ok, but the wait time goes up. It may not be a trivial amount of power and insulation is important.

Just for interest on the high temp spectrum, example heat treat oven rated at 1200C (2200F) with internal volume of 0.006 m3 (0.22CF) uses 1560 watts which is 250,000 watts per m3 volume.
https://www.soulceramics.com/collections/knife-ovens/products/evenheat-knife-oven-kh-414
 

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Make one Chris. Find yourself a discarded stove or oven - free shouldn't be too hard to find. kijiji. Cannibalize the elements and oven temperature control. Maybe even keep the enclosure and make it bigger.
 
You could make one of these to control the heat cycle they are cheap on eBay just check that it covers both temperatures mine just does Celsius ( who knew )!

28DFB867-1672-4005-88DF-B15FFFAA9E96.jpeg
 
Also, I see your SCR peeking out , what amp/voltage are u running througjh that? Ever have any issues ? I’ve had a couple fail but that I’ve chalked that up to chinesium




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On the right It’s a cast iron melting pot, and according to the tag good for 1000 degrees I’m hoping to give Babbitt a go. The control I bought off eBay and the SSR at Home Depot that’s rated at 20 amps it works good but I never thought to look at the Celsius display thinking it would display both F&C. I’m just using it for 120 v but the SSR is good for 250v.
 
I use a similar setup with an electric water heater element to heat my parts washer. I run 220v through the ssr, works good



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I belive that’s where I got it from....I’ll check next time I’m there.

Controlling and using a water heater element 120 / 220 volts is what I ended up watching on hops and barley mind you they use it for a still but have quite a few videos on building these controllers and SSR types that have to match your pid controller.

 
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