You may find this interesting;
http://www.allmetalshaping.com/showthread.php?t=11940
"John Escolano (jehammer1952) asked me how I made my powder coating oven, and so here's a brief how-to on this VERY useful tool for all people who have to coat metal products. Much better than painting, and often
easier!
1. Using 1 1/2" x 1 1/2" angle iron I built a 5'x4'x2' box.
2. Using the same thing I built a door frame.
3. Infill your frame and door with 1 1/2 insulated fiberboard NOT THE STUFF at Home Depot or Lowes. This stuff is yellow and has foil bonded to it. You get it at an HVAC outlet. Common stuff in various thicknesses. 1 1/2" is really all you need. My panels are not glued in, only tucked in behind tabs of angle iron or shelving pieces of angle iron. KEEP IT SIMPLE.
4. I recommend cladding only the OUTSIDE of the box, and BOTH sides of the door, with 26 gauge galvanized. I used a variety of 20 - 26 gauge depending on what I could scrounge. 26 is all you need. Pop rivet in place, but brake edges where you can.
5. Window in door is window from donor kitchen oven.
6. Donor kitchen oven supplied the two heating elements set in the floor tray. Wire both together (220).
7. On right side of oven you'll see a duct that leads from a black box down to the bottom of the oven. The black box is a
high heat fan which circulates the hot air from the top of the oven back to the bottom. It is 110 and operates on its own switch. Got it on eBay.
8. Door hinges are heavy duty and welded to frame.
9. Oven front frame has 5/8" fire stove gasket glued and strapped to it. This stuff is available in most hardware stores, or eBay. Make sure your door squeezes it all around when shut. Minor flaws can be dealt with the high heat caulk.
10. The tricky part is the electronics. I don't have a diagram any more, but I'll briefly describe the circuit:
a) 220 power goes into the gray box on the left side of the oven (Notice offset brackets to keep it away from the heat).
b) 220 is fed to a standard "contactor" (an oven relay/solenoid).
c) Contactor is controlled by a PID (computerized thermometer/timer). PID has a K probe that fits into bung welded in side of oven.
d) Above the oven is a 110 timer which controls a 110/220 relay which controls the PID-Contactor circuit. Timer off, no connection between PID-Contactor. Timer on, PID controls the contactor via temperature probe.
This thing worked PERFECTLY the first time I plugged it in, and has been a joy the last few years. My only problem has ever been using Caswell or Harbor Freight powder guns. I moved up to Columbia Coating guns last winter and it's super simple now. Holy smokes! Do you ever get a new group of friends when people know you can powder coat!
Couple of points:
1. 400 at 20 minutes is usually too much. 375 at 20 is better.
2. Oven takes 15 minutes to reach 400. KEEP the circulation fan running during the whole process, even during cool down.
3. During initial runs, the fiberboard will off gas A LOT. Keep fresh air moving in your shop. Several years into this, mine still off gases, though not a badly. I keep fresh air coming through the shop when baking.
4. Get the simplest PID possible. Bells and whistles are a hassle. I would not use the PID shown again.
5. A LITTLE leaking at the oven door, or elsewhere, is okay. You can explode powder coating theoretically, so a little leak serves as a pressure relief valve.
6. Shelf racks and hanging holes (see photos) are a MUST.
7. Took three days to build the oven. Two days to wire it. Total cost, less than $400.
8. Built it big enough to do a motorcycle frame (see one being built in one of the photos)."
