woohoo free powdercoating for challengers!
woohoo free powdercoating for challengers!
Buy me dinner first :)
Only other thing I did today was add a switch. The PID sends a 12v to trigger the relay, and I didn't really like that it starts heating immediately when you plug it in. I added a rocker switch on the 12v+ to the relay, and bingo. Now I can have it plugged in and do my settings and have control over whether or not it heats.
A million thanks to all of you who helped. This is a group effort and I couldn't have done this without all of you.
Why not mount the fan outside and have a little channel from the top to the bottom. I think that modification could be done with out to much hardship.
So when is Seventy Three Powder Coating LLC start up?
The way I have it assembled would mean a full disassembly of the skin to do that. I thought about doing something of the sort. My logic was that any fan I use will be transporting 400+ degree air, so it wouldn't matter if it's inside or out from a temperature standpoint. I think I just have it a bit close to the one burner. I'll try moving it to the top and see how it does.
As it is now, the fan got to 580F along with the adjacent walls at the bottom when the air was around 400. I'm hoping if I get it out of the direct, close-proximity radiation, it might melt less.
And a powdercoating biz as a side-hustle is definitely something I wouldn't mind doing.
Having worked on a couple oven cookers about the same size as your's. They had the fan on top and a channel about 1" deep and 3" wide inside and on the back wall. There was a hole on the top to the fan and it blew the warm air back down to the bottom through the channel.
It was very effective I remember when having to work on them.
Finally ordered some swatches from Prismatic and I'm 90% sure I'm going to order Anodized Bronze 2. Same basic hue as Triple Bronze but one tiny step darker.
https://www.prismaticpowders.com/shop/powder-coating-colors/PMB-2808/anodized-bronze-ii
Looks great, good job. Get some Candy Apple Red Powder Coat as seen on Ebay and paint some polished aluminum wheels. I want that stuff all over my whole car. 
There is one color they have is Spike Blue. It's a clear topcoat and it just POPs on polished aluminum. I gotta do that over some polished wheels some day.
Well, I powdercoated a thing! I had a chunk of square aluminum tube so I did a test piece. I prepped it eight different ways using a different abrasive on each side (4 sides) and doing alumiprep on one half (total of 8 different combos.
The four different preps were: nothing (control), wire wheel on a grinder, red scotchbrite, and 120 grit paper on a random orbit palm sander. Then the whole thing got scrubbed with simple green, and the one half treated with 25/75 Alumiprep for 5 minutes and rinsed.
Coating gun works very well. Even on the highest powder flow, it seemed better suited to smaller pieces. Maybe user error. I used about 20kV. Seemed to stick well enough, and the powder wrapped pretty well.
Ambient temps outside were 20F, so I was wondering if it was enough to prevent it from getting the oven up to temp, but it was 9 minutes flat to get to 400F.
Aluminum coated and in the oven. I figured with all the thermal mass inside, it would get up to temp pretty quickly, and it did. It was at 385F in a few minutes. This powder says part temp at 400 for 10 minutes, so I took a calculated guess and just closed it back up and set a timer for 15.
Downside.... I need to do some diag on my oven. I think the SSR is bad. In case you don't want to read back, I added a switch between the controller and the relay so I had easy control of when the burners were on and off. In past testing, the oven would kick them off at the programmed temp, and heat soak would take it a little past, like maybe 20 degrees. This time I noticed it got to 450 (programmed for 400). I opened the outer insulating door and saw through the crack that the elements were red hot. I turned off my relay switch and they continued to heat. I had to finish the bake by turning the breaker on and off a couple times to manually control it. Bummer, but here's hoping it's just a bad SSR.
The pre-baked coated piece: I checked it over with a bright light and sprayed a little more on one spot.
Notice how the outside steel skin of the oven is just about 10 degrees over ambient.
And the finished, baked piece. I POWDERCOATED!!!!! I did buy a digital mil thickness gauge. I don't necessarily need it for this, but I always wanted one to check panels on used cars before I buy. I learned I can lay the powder on about twice as heavy, and I'll need to learn how to be more even with my coats. The finished coat came out to 0.815 mil at its thinnest and 1.150 mil at its thickest. I should be shooting for 2-3 mil, right?
Next will be to subject the 8 different "zones" with some kind of mildly scientific test. Screwdriver scratch, hammer impact, drag a nail over it with 10 lbs on it... something.
Nice!
There are industry recognized tests with a hatch scratch pattern and a salt exposure for some period of time after that. I used to have the book on it but I got rid of it. You have the right idea with the nail test.
congrats on coating the first part, it isn't super easy to get started.
I'm very happy with the results. I thought for sure the un-sanded part would just flake off, but if I don't look at my reference marks that show where I did what, I can't tell any difference so far.
Back when I worked for a sign company, we had to wipe down all of the aluminum with lacquer thinner before welding or painting. No powder coating back then. How did you clean any oil off of the aluminum?
In reply to VolvoHeretic :
What I didn't include in the above post was that I started with the different abrasives, then a scrub with simple green, then a wipedown with acetone. Then I did the Alumiprep on half of the tube.
I labeled the tube with letters and numbers inside before coating so I knew which prep was on which face of the tube.
Congrats dude! That is so cool. Those PiDs are magical. I built a panel for an overly complicated RIMS 10 gallon homebrew system using two of them.
Question of the day. I suspected that my SSR was bad because it blew past my 400 setting and it appeared to still be heating (red burners). I ran it through another cycle today to test it and it behaved a little better, but it was also daylight so it may have just been that I was seeing more "leftover glow" last night in the darker surroundings. The PID is behaving and doing what it should, so my assumption was that it was just the remaining heat in the burners continuing to heat the oven for a bit.
If I set it to 200F, it will blow past 200 to about 220.
If I set it to 300, it will blow past 300 to about 340
Last night was the first time I went all the way to cure temp of 400, and it blew past it to 455, so I popped the door open for a few seconds. The burners were glowing pretty bright.
Is it a common failure mode for an SSR to stick closed? I mean, I did pay top dollar for the finest $14 SSR I could find. 
I'm sure it wasn't getting hot because of the oven, but I also didn't open the box to check if it was hot from amperage with live 240v and shaking cold hands either.
Later this evening I will open the box inside the shop and do some testing to see if the SSR is sticking on sometimes. It's not a huge deal, but it doesn't give me faith that I can set it and forget it. I'm going to be standing around and watching every bake.
Is it a bad SSR? Do I have the thermocouple too far away from the burners? Is the fan confusing the thermocouple?
In reply to Teh E36 M3 :
Thanks! I have a feeling I'm going to be powdercoating everything now.
Maybe attach an "on" light which is on the burner side of the ssr. This way you can verify it is open or closed corresponding with the PID's command. I do also know that the PIds take a few runs to 'learn' the latency of the burners. I did this on my brewing setup and I liked it just to see how it all acted. Also put in a red cutoff switch that you just hit to cut power to the whole system.
In reply to Teh E36 M3 :
Those are good ideas. I put a low-volt switch (enable launch in the photos) between the PID trigger and the relay so I can control the signal, but if the SSR is stuck closed, you're right, that wouldn't do anything. Right now I'm just using the breaker which is about 10' away from the oven, but a switch and a light between the relay and burners couldn't hurt. I guess I'm researching 40 and 50A switches now :)
Yeah, the 'on' light is just a good diagnostic tool, and emergency off switch probably won't fix a stuck ssr, as if I recall, it does the same thing as your launch switch accomplishes.
I'm finding that a 40A switch is either expensive or huge. I found a Leviton light switch rated for 600v and 40A, but it's $72. I also found some cheap 3-phase rotary switches, but I know little about how they function inside. They're also huge and I don't think I can get them inside my box (giggity).
If I had the room, I would just get three residential 15A switches, but I don't think I do.
In reply to Curtis73 (Forum Supporter) :
A 3-phase switch should have 3 switches to turn off 3 wires. While not ideal, you should be able to shut down your elements but you will still have 110v to one side.
I would be tempted to use 3 of these. One for each element. Then use your light switch to energize the coils. Then when it's off, it's all the way off.
In reply to Toyman! :
The way it's wired, I have three wires coming off the relay, one for each of the burners, so a 3 phase switch would be perfect as long as it just connects terminals and doesn't combine anything. Instead of three phases, I'm using three conductors. I don't think the switch will care what the phases are running through it. The other side of the burners returns to a bus bar with another line of 120v, so they'll always be 240v. And you're right, they'll always have 110v from that second bused leg, but they currently do now as well. I'll put together a wiring diagram some day.
So I could do it with a three phase switch, one conductor to each pole, or if I find a heavy-enough switch, I can just gang all three conductors on one pole of the switch.
Part of the reason I'm doing this is to prevent the burners continuing to heat if the relay fails, so I don't really want to add another relay, although the chances of both relays failing simultaneously is pretty slim.
OK, really crude diagram.
The switch won't care.
If you have one leg of the 240 running through the relay to each burner, then wire your switch on the other legs. That will kill all power to the burners when the switch and relay are off as well as kill power if the relay fails.
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