Since it's been in the 40's lately, which means my garage is in the 60's, it's been taking forever for paint to dry on parts before I hydro dip them, so I needed an insulated box to heat up the parts and get them to dry. After sketching a large, complicated box with fiberglass insulation and electric heating elements controlled by a thermocouple and Arduino and seeing the 3 digit price tag and 8 hour build time I decided to come up with something that breaks a fundamental law of nature: good, fast, or cheap, pick 2. I picked all 3.
Step 1: Acquire the Parts
This is a very low parts count project and everything can be found at the same place, assuming you don't have some of it already.
1> 6 anti-fatigue mats with jigsaw edges. These vary in size and price, but it's not overly critical as long as they have jigsaw edges for joining the pieces into larger mats. Mine are about 24" square and came from Harbor Freight for under $10 per 4 pack.
2> Small electric floor heater with thermostat. The thermostat isn't critical, but it will simplify your life a bit. Smaller is better here, you'll see why later. It doesn't have to be insanely powerful, either.
3> Turkey frying thermometer. While I'd love to have a digital thermometer with a remote display, there's no point. A long cooking thermometer meant for checking the temp of a large vat of oil works.
4> Shoe box. This is just something to hold the parts off the floor, no need to overthink this part.
Step 2: Build the Box
First, build the box. Unwrap the mats and pick 6 for your box. Most of the mats I've seen have strips along 2 edges that leave a more finished edge. They just dovetail onto the jigsaw edges. Remove those and set them to the side. They won't be used here, but you never know what you might need them for, like the edges of mats you actually put on the floor.
Pick two mats, stand them on edge at 90° to each other, and interlock the dovetails. I like to have the bottom of the mats facing in, but not for any good reason. Once those two are together, add a third, then a fourth. Some mats have an interruption in the jigsaw in the middle of each side. Ignore those and keep going, the small gap isn't going to be an issue.
Now you should have a topless, bottomless cube. Grab the 5th mat and lay it on top of the cube. I find it easier to interlock the corners, aligning the cube, then work my way around. whatever works. Once the 5th side is secure, flip the cube over and add the 6th side, but only interlock one edge for now.
Step 3: Fill the Box
Almost done. Stand the heater on one side a couple of inches from the sides of the box. Run the cord either out the top or through an edge somewhere, whichever works best for you. Put the shoebox opposite the heater. The pictures show the heater blowing directly on the parts, but I've since rotated the heater 90° for indirect heat. I don't know if it works any better, but it keeps me from worrying about melted parts. Now hook the thermometer over the edge directly above the shoebox.
Step 4: Fire It Up!
Now it's time to cook some parts. Put your parts on the box, turn on the heater, and close up the top by interlocking the edges. Chances are you'll have to play with it to get the temperature you want, but once it's set it doesn't vary much. Just unplug the heater and leave the knob alone. my setup, in a 65° garage, runs for about 20 seconds every 3-4 minutes at 150°. Just don't leave it unattended.
The pictures show a set of Axial Wraith 2.2" RC truck wheels I hydro dipped in digital urban camo. The clearcoat was taking forever to dry, which led to this Instructible. After 30 minutes in the box the lacquer was dry, hard, and glossy, better than I've ever manage in open air.