Solar ovens hold the potential of revolutionizing how 3d printed waste is recycled. This page is a gathering spot for bringing the various aspects of exploring solar ovens for this purpose together as development continues.INSPIRATION
There are loads of videos on YouTube where people show themselves baking bread or some other food in a solar oven. Since bread normally bakes at 350° (176° celsius) Fahrenheit, I thought a solar oven would be good for melting 3d prints.
The following two videos by were very encouraging for melting 3d prints even though the videos are about melting HDPE.
High-Density Polyethylene (HDPE)
“Now that we know what it is used for, let’s examine some of the key properties of polyethylene. PE is classified as a “thermoplastic” (as opposed to “thermoset”), based on the way the plastic responds to heat. Thermoplastic materials become liquid at their melting point (110-130 degrees Celsius in the case of LDPE and HDPE respectively). A useful attribute of thermoplastics is that they can be heated to their melting point, cooled, and reheated again without significant degradation. Instead of burning, thermoplastics like polyethylene liquefy, which allows them to be easily injection molded and then subsequently recycled. By contrast, thermoset plastics can only be heated once (typically during the injection molding process). The first heating causes thermoset materials to set (similar to a 2-part epoxy), resulting in a chemical change that cannot be reversed. If you tried to heat a thermoset plastic to a high temperature a second time, it would burn. This characteristic makes thermoset materials poor candidates for recycling.” – Creative Mechanisms
The web page below is about a recycling process that converts plastics to large sheets. The video below it shows people who used these sheets as a roof.<h2 MATERIALS
|ITEM||WHEN ADDED||WHEN REMOVED||WHY REMOVED|
|Heavy Duty Aluminum Foil||start|
|Biscuit & Brownie Pan||start|
|Project Display Board||start|
|Decorative Mint Stones||start|
|Glad Cling & Seal||start|
|Solar Oven Project Clips||2nd trial|
|Copper Foil sheet||2nd trial|
|Electrical Tape||2nd trial|
Foam Cooler, 26 Quart, from Dollar General. The cost was $513. The measurements are height, 12.75″; bottom 7.375″, and top 17″ x 12″.<h3 Heavy Duty Aluminum Foil
Heavy Duty Aluminum FoilDollar General$3.95Biscuit & Brownie pan11 x 7Dollar Tree$1.25
My eyes were starting to bother me while using the foil indoors. It really is quite reflective. I bought glasses from Home Depot to wear indoors and outdoors.<h3 Biscuit & Brownie Pan
Biscuit & Brownie pan,11″ x 7″ from Dollar Tree. The cost was $1.25.<h3 Project Display Board
Project Display Board from Dollar Tree. The cost was$1.25. The board was used to make reflectors.<h3 Decorative Mint Stones
At the end of August 2022, I asked for suggestions in a Creality Facebook group for increasing the oven temperature. One person suggested using “black painted tiles or bricks at the bottom.” I asked if the rocks at the bottom were good for storing and releasing energy. The response was, “yes rocks are good thermal mass, but if you put too much, it’s longer to heat up. In you’re case if it’s high temps that you want, you can use a little to no mass.”<h3 Glad Cling & Seal
Cling wrap is Polyethylene. I found it works a lot better than borosilicate glass at containing heat in the oven.<h3 Parchment Paper
Parchment paper prevents the melted plastic from sticking to the pan.<h3 Solar Oven Project Clips
Solar Oven Project Clips were 3d printed. The clips will be redesigned before the next trial.<h3 Copper Foil sheet
When I asked for suggestions in the Creality Facebook group that I mentioned earlier, one person suggested using a black tarp “to increase the air temperature around the box.” The following was my response:
I’ve seen where most people have either spray painted the inside and use[d] black pans or pots. Spray painting is a problem for me since I live in an apartment complex. I suppose I could take the setup to the park and spray paint there, but I’m not inclined to attempt that until I see some proof that the black color makes a difference. I haven’t seen it yet.
This is the first I’ve seen about a black tarp. I see that I can get one for about $10 on Amazon. The tarp is polyethylene. Looking up thermal conductivity…. high density-0.45 to 0.52 W/mK. Aluminum foil – 235 W/mK. Yeah, foil is a better conductor. Since I looked that up I might as well check mylar paper because I was thinking of using that…..Mylar paper-0.14 W/mK….
….Thanks to your suggestion, I found this list – https://en.wikipedia.org/wiki/List_of_thermal_conductivities. I see that copper has about twice the conductivity of aluminum and is affordable. I’ll try that next.
Thermal conductivity for pure copper is 401.
“W/mK stands for Watts per meter-Kelvin. It’s also known as ‘k Value’. The comparison of thermal conductivity can be measured by the ‘k’ value. The k value, or Thermal Conductivity, specifies the rate of heat transfer in any homogeneous material. If a material has a k value of 1, it means a 1m cube of material will transfer heat at a rate of 1 watt for every degree of temperature difference between opposite faces. The k value is expressed as 1 W/mK. The lower this value is, the less heat the material will transfer.
This can be very helpful in selecting the thermal materials you might need when attaching a heatsink to a component and is a specification filter to help narrow the options for Thermal pads ” – Michael McGrath<h3 Electrical Tape
The tape was needed for attaching the copper sheet. This will be replaced with Kapton tape in future trials.<h2 BLOG POST LINKS <h2 VIDEO LINKS