Instructables

Step 15: Performance Improvements

Picture of Performance Improvements
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The very first test showed that the temperature reached 225 degrees Celcius in 520 seconds, and 260 degrees Celcius in 900 seconds. This is a little too slow.

I then raised the rack about 1.5" closer to the top heating element, and sealed most of the holes and tiny seams inside the oven using aluminium tape. This isn't the smartest idea since I had no idea what temperature the adhesive can withstand, but it seems to be OK.

After these changes, the temperature reached 225 degrees Celcius in 360 seconds, and 260 degrees Celcius in 570 seconds.

Then I applied a layer of aluminium tape to the front glass door, covering the bottom 2/3 of the glass door. I then performed another test: 225 degrees Celcius in 320 seconds, and 275 in 560 seconds.

This is just fast enough for reflow soldering according to the temperature timeline that I am following, but more improvements would need to be made.

I stuffed the inside of the oven with a layer of pink fiberglass insulation. This stuff is not electrically conductive and can handle a temperature of 500 degrees Celcius. It is safe for use in my situation.

I also found a large brick to place in the oven. The purpose of the brick is to occupy volume so there is less air inside the oven to heat. The brick is covered with aluminium foil to stop it from absorbing heat too fast. This brick actually did not get very hot, it is actually cooler than the surface of the glass door. It does its job exactly as I expected it to.

I am very happy with the final results: 225 degrees Celcius in 300 seconds, and 275 degrees in 540 seconds. I can reach the end of the "soak" stage in just 3.5 minutes.
 
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charlieb0002 years ago
if i build one its going to be with ole fashioned bits and peices, rather than bits and bytes!! step 15: you do realise the brick acts as a heatsink? if its at the bottom then i guess its ok. but the aluminium is a nice thought, though it may work better if the whole inside were coated. you have a "minute" typo here
frank26080115 (author)  charlieb0002 years ago
the brick is acting like a heat capacitor, it will absorb heat while the air is hotter and release heat if the air is cooler, but it also reduces the amount of air inside the oven. Air also acts as a heat capacitor, and also a heat resistor.

it doesn't help heat dissipation to the outside of the oven that much, if at all, so it's a net benefit.

In the end, it does help the oven heat faster, but the oven also cools slower. opening the oven door slightly will help it cool faster so that's not a problem
I think you did a great job, and so what if you have typos? - Celsius and aluminum ( I still knew what you meant )... :)

BTW, I am trying to repurpose 2 small appliances. I have a working coffee maker and a working toaster oven (both replaced with newer gifts). I like your project, but It's really not that useful for my needs. Just out of curiosity, do you have any other suggestions for reusing these appliances (or just taking out useful parts)?

If I can't come up with anything, I will donate them to either the Salvation Army or someone who wants them (and is willing to pay for shipping) - I posted this in the Q & A section the other day.

Would love to hear your ideas/feedback if you have any to share.
frank26080115 (author)  canucksgirl2 years ago
Thanks

I can't really come up with any other projects with those things, if they are working, personally I would just keep using them, or donate them. Just don't trash them.
if it were a simple mispellling i would have left it, it ought to have said "second". btw, the spelling/pronunciation of aluminium/aluminum depends on where you are from.
frank26080115 (author)  charlieb0002 years ago
oh I was looking for the mistake but spell check didn't pick anything up, now I fixed it since you pointed out it was supposed to be seconds, thanks.