My convection oven

[high standard 40]

I am fairly new to powder coating. What I have learned is that even with a quality oven, it can be challenging to maintain a constant temperature for curing powder coat. At first I would preheat my convection oven to 400 degrees and wait for it to stabilize at that temperature, as monitored by two different thermometers. I would then place my tray with the bullets in the oven. The temperature would drop considerably as the oven tried to maintain the 400 degree setting and bring the contents back up to the setting. In that effort to rapidly reheat the oven, the temp would swing far above 400 degrees and then take a few minutes to settle down to that setting. I came up with a new technique that works well for me and may help others who have the same issue. I don't preheat the oven. I place the tray in the oven first, then turn it on and set for 400. I have found that using this method the temperature doesn't go above the 400 degree setting because it evenly heats the oven and contents together so when it reaches 400 degrees it stabilizes at that point. By then the powdercoat has melted and I can begin the 20 minute cure time. It works very well for me using this method.

[TjB101]

Are you running the toaster in regular bake mode or convection mode? I have a convention unit but have just run it in bake mode. Preheating it before putting in tray. Seems to not overshoot to much at my 400 setting.

[Cast10]

I run mine on Convection Mode and preheat with 450. After it reaches 400, I set it to 425 and monitor with an oven thermometer. Once it starts over 400, I set it to 400 and it holds until I open the door. If it stalls a bit after loading the tray, I’ll put it back on 450 until it hits 400, then back to 400 setting throughout.

[high standard 40]

Are you running the toaster in regular bake mode or convection mode? I have a convention unit but have just run it in bake mode. Preheating it before putting in tray. Seems to not overshoot to much at my 400 setting.

I run it in convection mode. My understanding is that it's supposed to heat more evenly that way

[Hossfly]

If you add mass to the equation, things work better.

[HATCH]

I run it in convection mode. My understanding is that it's supposed to heat more evenly that way

In a perfect world yes.
Convection mode is suppose to have a fan that circulates the air so the heating is even.
In our application, I am not sure if there is any real advantage to convection vs regular baking.

The oven I use is a convection oven because it was priced right

[Conditor22]

I run mine on convection and put a heat sink (ceramic BBQ briquettes, you can use anything that holds heat) on the bottom to help it recover faster.

* every time the surrounding temperature changes the internal temperature will change without changing the setting due to the location and type of thermostat on the countertop ovens*

https://i.imgur.com/IBgRs5O.png

I ended up wiring a PID to my oven putting the fan on a separate circuit, it now heats up faster, maintains temperature :)

top PID for the oven (yes that's a computer power supply box, works great), bottom PID for casting
https://i.imgur.com/ZBRPSHX.png

[plainsman456]

I have a Oster oven and turn on the fan setting and temp to 400.

When the first pan of boolits are ready to go in i turn on the oven for about 2 minutes.

Place pan and turn timer past 20 minutes then come back to 20.

So far it has worked every time.

[a.squibload]

I have a plain toaster ($10, thrift store). Tried low temp method,
seems to work but have settled on 400° for 10 or 11 minutes.
Large or small batches, no difference.

A friend ran his a little too long and the boolits slumped out of shape!
He said it was around 400°...

[high standard 40]

I have a plain toaster ($10, thrift store). Tried low temp method,
seems to work but have settled on 400° for 10 or 11 minutes.
Large or small batches, no difference.

A friend ran his a little too long and the boolits slumped out of shape!
He said it was around 400°...
I can't see the bullets slumping at 400. He must have trusted the dial to be accurate. Was he using an accurate thermometer?

[a.squibload]

Sorry, been a while. He doesn't have a thermometer so coulda been a million degrees.

[charlie b]

I had same kind of problem with mine. They I realized the problem was me.

When I put in the trays of bullets I was setting them close to the door. Turns out that blocks the airflow.

Set the trays in about an inch and now have very consistent temps.

And do measure your temps. When set at 400 my oven is at 450F. When set at 375 it is 400F. If I set the oven to 450F on the 'dial' it will melt the bullets.

[Hossfly]

Last night I used the tc in boolit method. With 300 pc lt blue 45ACP 200 gr boolits. Conv. Oven toaster set to bake and fan on dial set at 425’ monitor therm fluke reading 400’ ran for 30 min. Perfect, smash test, perfect.