Insulating a Reflow Toaster Oven - Page 1
Forum section: electronics / general

author: Po6ept
author_rank: Regular Contributor
timestamp: January 03, 2014, 05:18:52 am
content: I just finished building a reflow oven using a B&D TO1675B toaster oven, an Auber Instruments ramp/soak PID, and a 40A SSR. I added a 12v supply to run a couple of cooling fans for the controller compartment and used a heatsink from a discarded Pentium computer for the SSR. I am somewhat happy with the result, but it takes too long to ramp up at each step in the reflow profile.I tried wrapping the oven in the fiberglass insulation from flexible heating ducts. It passed the flame test, but in actual use the insulation smokes, discolors, and releases fumes where it is closest to the heating element ends and the top of the oven. I need to find some sort of high-temperature blanket about 1 cm thick to wrap around the oven.Does anyone have any ideas? I checked my local auto parts and home stores and they have nothing that will work.Thanks,BobHere are a few photos of the oven:

author: GeoffS
author_rank: Unknown
timestamp: January 03, 2014, 05:24:59 am
content: High temperature insulation fabrics and boards can be found at refractory suppliers.There are good for at least 1000° - 1400° C which should be enough for a toaster oven.

author: orion242
author_rank: Unknown
timestamp: January 03, 2014, 05:39:58 am
content: Quote from: GeoffS on January 03, 2014, 05:24:59 amDitto. They use the same type of materials around boilers and electric heaters. HVAC suppliers may be another avenue to get some.

author: GeoffS
author_rank: Unknown
timestamp: January 03, 2014, 06:06:31 am
content: Quote from: orion242 on January 03, 2014, 05:39:58 amI don't think HVAC insulation would have a high enough temperature rating. It's probably only rated to 200 - 250 degrees,

author: Po6ept
author_rank: Regular Contributor
timestamp: January 03, 2014, 06:17:27 am
content: Refractory was the word I needed. A search using that term turned up three local companies that specialize in those supplies. The search led me to a product called Kaowool that looks to be exactly what I need.Projects like this one make me wish we had 240V mains in the US. It would be nice to simply add heating elements.I appreciate the help.Bob

author: SeanB
author_rank: Super Contributor
timestamp: January 03, 2014, 07:54:41 am
content: Get a drier socket installed in the area you want to use the oven, then get 220V elements or use 2 110V heaters in series on the drier outlet. You will need 2 SSR units though, one in each power lead, to switch them.

author: amyk
author_rank: Super Contributor
timestamp: January 03, 2014, 08:18:04 am
content: Mica sheets will also tolerate those temperatures.

author: Po6ept
author_rank: Regular Contributor
timestamp: January 03, 2014, 09:19:46 am
content: I'll post the results. You may be right about the insulation, but the oven loses heat quickly when power is removed so I figure it's worth a try. If I don't get good results, I may try rewiring it with another set of elements and another SSR to use my 240V power tool outlets in the shop. It all depends on how well it actually performs on a couple of test boards. An extra 90 seconds at each stage in the profile may work just fine in real life.

author: orion242
author_rank: Unknown
timestamp: January 03, 2014, 10:18:40 am
content: Quote from: GeoffS on January 03, 2014, 06:06:31 amThe stuff that surrounds fire chambers in boilers will.

author: SeanB
author_rank: Super Contributor
timestamp: January 03, 2014, 10:30:46 am
content: Glass fibre wool is what you want. WARNING ABOUT THIS WOOL is that it contains short fibres that break easily and will get under your skin and itch like crazy, leaving welts. You get it in sheet form with a fabric layer on each side so only the edges are exposed. DO NOT cut this inside the house, go outside and use a pair of good scissors to trim to size, then place the offcuts in a plastic bag and throw them away. Wash the scissors well before taking them back indoors. WEAR A FACE MASK. WEAR LONG SLEEVE GLOVES and throw them away, thin garden gloves are fine or even surgical latex gloves. Get a sheet of Mica and cut covers to place on the top and sides over the wool, and place it there with either tabs or with wires. Vacuum the fibres into a disposable bag vacuum with a new bag that you throw away after use. You can wash the hose inside and wipe down the exterior to remove fibres using running water in a sink. That way you will have good insulation.

author: GeoffS
author_rank: Unknown
timestamp: January 03, 2014, 10:38:56 am
content: Assuming the toaster oven gets to 230°, glass wool would be close to its temperature limit of around 260°C,. You really want a bigger margin than this, hence the recommendation of a ceramic based insulation.Kao wool or similar is readily available and not too expensive.The recommendations for handling ceramic wool are the same as those given here for glass wool.

author: Unknown
author_rank: Unknown
timestamp: January 03, 2014, 01:13:58 pm
content: I use "ceramic fibre blanket" in my pottery kiln which is good for 1300 c - but remember to get the body soluble stuff!

author: Vincent
author_rank: Regular Contributor
timestamp: January 04, 2014, 01:51:31 am
content: If you can find an old cooking range somewhere, those are insulated with ceramic fiberglass-like insulation. It seems to be quite good stuff for high temperature applications.

author: mjrandle
author_rank: Contributor
timestamp: January 04, 2014, 02:36:43 am
content: I used a welders blanket wrapped in aluminium foil and installed it on inside of oven. Works a treat.Regards,Mike

author: MacAttak
author_rank: Unknown
timestamp: January 04, 2014, 09:46:17 pm
content: If you're having trouble getting the oven to heat quickly enough, you can add more heater elements - can find them for about $10 each on amazon.com in many sizes and power levels.I sealed up all of the crevices and holes in the oven compartment using ceramic cloth tape (same stuff used by some 3D printer extruders to wrap the hot-end) and kapton tape - so no heated air can escape the compartment.Also, look for Reflect-A-Gold tape. It is sold to auto racing enthusiasts and is usually used to protect components in the engine compartment from high radiant temperatures. A large roll should be enough to coat the inside of a small oven - so you might need two rolls since this oven looks larger than most. It is HIGHLY reflective - I made the mistake of shining a high-brightness LED flashlight into my oven after coating the inside and was partially blinded for a few minutes.With extra element and the reflective tape, I found that my oven was heating uptoo quicklyand I needed to tune down the heater cycles (using on/off cycle patterns instead of PID). To achieve the desired cool-down post-liquidus I also have a buzzer that lets me know when to open the door - otherwise it retains heat too well.

author: Timon
author_rank: Newbie
timestamp: April 20, 2014, 04:07:29 pm
content: Quote from: Vincent on January 04, 2014, 01:51:31 amThere are several sites that sell cooking oven insulation and since most ovens go to 500 F, 260 C, which should be fine. I would expect that the melting temp would be at least 20% higher than the ovens rating.

author: frogblender
author_rank: Regular Contributor
timestamp: February 28, 2017, 03:41:01 am
content: Po6sept.... how'd this turn out for you? Success, or unfortunate lab-on-fire event?

author: Po6ept
author_rank: Regular Contributor
timestamp: March 01, 2017, 03:45:26 am
content: I haven't started any major fires but I did cook a couple of boards before I got the hang of things.I used an Auber instruments SYL-2342P ramp/soak PID controller. It's a bit awkward to program but it lets me switch between reflow work and powder coating small parts by punching in a new routine.I found a used oven with three top and three bottom elements. It was originally wired to turn on either the top or the bottom set on 120V, so I rewired it for 240V by placing both sets in series. The glass fiber wool works, but it melted around the ends of each heating element. If I used it more often I would take it apart and replace the glass wool with a ceramic insulation. With all the elements going it heats fast enough to follow a pretty decent reflow profile.I'm pleased with the outcome and think it was a worthwhile project. I don't use it often but it's let me finish a few projects I would have skipped otherwise.

author: VK3DRB
author_rank: Super Contributor
timestamp: March 01, 2017, 12:10:10 pm
content: Thanks all for the good info.I have a ControlLeo2 and a nice toaster oven, but have not got off my backside to construct it yet. Insulation is a key to success and I will look into the welder's blanket.http://www.ebay.com/itm/4-X-6-Welding-Blanket-Welder-Safety-Tools-Protective-Gear-for-Mig-Tig-Arc-/111750824095?hash=item1a04de409f:g:X1oAAOSwDNdV2PRxAsbestos blanket out of old gas heaters would work a treat, but the downside is you risk getting cancer and dying a slow and agonising death. You could email a sociopathic James Hardieexecutive and ask if their human resource can make a special asbestos lining for the oven encased in foil for you.But seriously, the welder's blanket folded over a few times might work a treat. This carbon fibre stuff might be the go. Very cheap:http://www.ebay.com.au/itm/Carbon-Fiber-Welding-Blanket-High-Performance-plumbing-shield-heat-1-4-thick/152224486179?_trksid=p2047675.c100010.m2109&_trkparms=aid%3D2220072%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20140122130056%26meid%3D0be91990b04441da882d2d79886a7753%26pid%3D100010%26rk%3D3%26rkt%3D4%26sd%3D170992354823I just bought a larger carbon fibre blanket from that vendor in Oz. I'll let you know how it goes with insulation.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: March 02, 2017, 03:02:32 pm
content: In my oven the warm up profile was less of a problem than cool down. You may be trading one problem for another. Of course cool down is somewhat easier to correct with external airflow, but be ready for one more step in your journey.