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Cheap low-temperature oven
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ezalys:
I'd like to make an oven for curing adhesives that require an elevated temperature for a proper cure. I'd like for the temperature to be settable from 60 degrees C to 75 C plus or minus 5 degrees over time, and over the volume of the container. I'd like for the volume to be about 6" x 6" x 6" or 15 cm x 15 cm x 15 cm.

Primary objectives are to keep the cost down and to make the oven out of easily available materials from home depot or mcmaster carr or similar. Ideally would prefer to repurpose some home appliance. The ideal for me might be just repurposing a toaster and adding a temperature controller to it, but I worry about a toaster having consistent temperature through its volume. This feeeels like something that someone must have bodged together at some point, tried, experimented with, and therefore has experience with. I'd love to hear from them.

I think the weird part here is the low temperature. Tons of people have done SMD reflow ovens. I'm wondering about how a toaster will function with such a low setpoint. I do, fortunately, have a fan that's good up to 90 celsius, so I could stick that inside to agitate the air inside somewhat. I think my hesitancy to try this mostly is due to having experience with dedicated low temperature ovens that feature a boatload of insulation (take for example https://www.globalindustrial.com/p/medical-lab/laboratory-equipment/le-laboratory-shakers/steel-door-incubator-10-180-270w?infoParam.campaignId=T9F&gclid=Cj0KCQiAg_HhBRDNARIsAGHLV520X3p0496UjQs_pm782ODjZq3ah3Ju1ZMHENPwxVry78agLIucDPUaAgpnEALw_wcB ). That insulation must be there for a reason. I just wonder what, quantitatively, I'm giving up by not having it.
DaJMasta:
I wouldn't expect a toaster to do that low, but try an egg incubator.  Something for bird/reptile eggs may be able to go that high.


Conversely, you could try hacking a toaster oven's thermal controls to do it, maybe disabling a heating coil or just reducing the current through one for a slower response and finer PID control.
jmelson:
A toaster will do FINE with an added-on thermostat.  You might also need to provide some kind of power limiting, so the heating elements never get over XX% of full power.  Some thermocouple temperature controllers might be able to handle that.  Now, a big volume of adhesive in a roughly cubic pot is not going to heat evenly.
But, putting a thermocouple on the side of the pot should give good control of the temperature of the OUTSIDE of the pot.

Jon
ezalys:
I would absolutely add a PID controller to the thing. Sorry, by use a toaster oven, I meant use a toaster oven with some custom controls.
ConKbot:
Definitely a convection toaster oven for even temperature, plus a PID controller (from Omega engineering if you want it to just work reliably, or ebay if you want it cheaper)  and a SSR for switching the elements. Since you're in 120V land, rewire the heater elements in series so they would be in a nominal 240V configuration, so you'd drop the power to 1/4 of original or just disconnect some if you only need 1/2 power, etc.

If you get a PID controller with an auto tune feature, let it tune itself with a medium-small size chunk of metal inside to let it have some thermal mass to tune to, but not an excessive amount.

Make sure to keep thermal fusing and normal fusing in place.

I use an omega temp controller, +SSR to control a heater for a snake terrarium, and with the output on a 1s period (No need for slower, as there are no mechanical contacts to preserve) it stays within 1degree F all the time. Just had to let it auto-tune for an hour or two before adding stuff to the inside of the tank.
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