Attention engineers, curing oven controls.

[Brian_216]

Ok guys, I know there are lots of talented individuals here with many different backgrounds. Rage Composite Works is taking it to the next level and we need a hand. We are making a serious post cure oven. I already have a military konnex, and a Dayton ceiling mounted propane heater. I should note the unit is located a good 40 feet from any buildings and the high limit will be disabled. I'm in need of heat controls. More complicated than I'm really comfortable with. We need a timer, and ramp / soak controls. I'm ok with a 5 to 10 degree fluctuation but I'll need it to hold a minimum of 180f, and max of 225f. A possibility of convection fan control being built in is also a possibility.

So here is a breakdown of what I want.

Push a button for initial cure.
Burner will fire and fans will engage
Temp will come up to 110, acticate a timer and run 2 hours, and turn off.

Push second button for post cure
Same as above but 200 for 3 hours and turn off.

I think a standard PID controller will cycle the burner way too frequently due to the precise nature of a PID

My last and cheap option is gut the controls from a household oven and use the relay that turns the elements on to trigger the burner.

Thanks.

@ocdsolutions @DAG

 

[DAG]

Sounds like a fun project. I'm a mechanical guy. I've done a few logic control projects but don't have access to labview in my dayjob. @Matt_E and @Tyrant1919 @boyer
might be some brains to pick

 

[OCD Solutions]

I'm out of town for the weekend and not able to get to a computer to look anything up but there are plenty of standalone burner controllers that you could adapt easily enough.

Honeywell and Omron are the names that come to my mind but I don't remember the model number that we were using.

What's the safe operation range of that heater and what is the ignition method?

 

[OCD Solutions]

Check out kiln controllers. You may find something that's already close to what you need.

https://www.bigceramicstore.com/info/ceramics/tips/tip77_kiln_electronic_controller.html

 

[OCD Solutions]

Here you go, $128.

http://www.thermomart.com/Dual-Digital-Temperature-Controller

 

[motobehrens]

My favorite part of those controllers is toggling through a thousand menus and a million parameters using only three buttons.

Post a pic of your contraption. It sounds like an interesting project.

 

[OCD Solutions]

You got that right. The original setup process is a bitch.

 

[Brian_216]

I'm out of town for the weekend and not able to get to a computer to look anything up but there are plenty of standalone burner controllers that you could adapt easily enough.

Honeywell and Omron are the names that come to my mind but I don't remember the model number that we were using.

What's the safe operation range of that heater and what is the ignition method?

Safe range has been found lol. I think it's hitting the high limit and shutting down. I ran it for about 2 hours tonight and only got close to 120. I'll get some good pics tomorrow. I managed to tweek the wall thermostat to get up into the range I need for now to see what it's capable of. Tomorrow the high limit is getting disabled so I can find out if 200f is even a possibility.

 

[Brian_216]

 

[motobehrens]

Given the location of your heat source, you may have an issue with temperature uniformity. Pick up a handful of thermocouples and stick them to the front, middle, and rear of your product, and some on the ceiling and sides, so you can monitor actual temperatures. Log that data so you can see your hot and cold spots. I would place the control tc for the pid controller as close to the center of your product as possible. You may need a couple fans inside to help distribute heat. You can pick up a pack of stick on Thermocouples with connectors from Omega.com. All that might be overkill if your product isn't very process sensitive, but it is good practice to know your temp deltas to help improve the process.

 

[Brian_216]

Well I'm up over 140 now with high limits bypassed and I cut the hole for the burner exhaust and vented it so it's safe to go inside. I noticed with a laser temp gun the ceiling is hitting 160 and the parts are near 140. I will be adding circulation fans. This will definitely aid in the curing process.

These could have been ready to use a lot sooner if I wasn't waiting on nature to cook them.

 

[blaster800]

SHELBY MCCLEELLAN does all the controlls for the paint baking ovens at body shops ! contact ''SPORK '' on here , im sure he can make it do anything you want !

 

[Brian_216]

I didn't even think of that. I work at a body shop and see a paint booth with a gas fired air makeup every day. That would be perfect.

 

[hydrostyler]

I know you guys have built a ton of composite parts, but isn't the idea to post cure your parts in the mold under vacuum to avoid warping?

 

[Brian_216]

We do the initial cure in mold around 125f for 2 hours. Secondary post cure close to 200f out of mold I have not seen any warpage. I can't keep the molds tied up that long with the backlog I currently have.

 

[SuperJETT]

Take a look at any electrical wiring because THHN insulation is rated for 195F and you may get some breakdown/issues from continuous cycles to 200F with overshoots above that.

 

[Brian_216]

Take a look at any electrical wiring because THHN insulation is rated for 195F and you may get some breakdown/issues from continuous cycles to 200F with overshoots above that.

I'm relying on the power vent drawing air through the burner for that lol. I have a 6" duct feeding the side panel where all the wiring is for both outside combustion air and cooling of the electronics. Maybe a temp sensor in there to be a failsafe at 190. Or I'm moving all the electronic components outside the oven. The final post cure calls for 125 to 225 from 2 to 6 hours. Good call on the wiring.

 

[OCD Solutions]

Have I got a deal for you, lol. I misordered and got 25ft of a thick fiberglass wire protective sleeve that you could use to protect all the wiring up to 700F.

 

[Schmidty721]

Cool to see you guys progressing even more!
Are you still infusing or going to Pre-preg now with the curing capabilities?

 

[Jakobi86]

I built a temp controller for my powder coat oven. It's a PID temp controller off of eBay. I have it set to ramp to a preset temp, hold that +\- a degree and wait for me to turn it off. It does have features for safe limit, alarms, cool down time after a timer is set, pretty much all the stuff your looking for. It was like $50 and has the three buttons to scroll through the entire menu (sucks) but it works for what I use it for


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