I have been working on this for a while. I didn't want to pay over a hundred dollars for a 4-spool heater that was mediocre in heating the filament. The box is more effective than I thought it could be. When I had 7/9 spools loaded the humidity went up to about 80% then as it stayed heated the inline desiccant sucked out all the moisture and it went down to 15%.

I started with M3 screws but found they did not give me the rigidity I was looking for. You can use TPU as listed for the grommet but any material will be fine (TPU gets you a better seal). I tried PETG and ABS for the heater element and spacers but they all melted. The heater gets up to 275 degrees Fahrenheit and the internal temp I have seen in a solid 167 degrees and that works perfectly for PC to PETG and Pla. I strongly suggest you use PC (Polycarbonate) all linked below. I have been running it for 2 weeks now and it is not melting at all. I am an Amazon affiliate, and I would love it if you would buy from my links! Thank you very much.

I grabbed a sealed box from Amazon 50 quarts or around (any of them will work and I will link one below). Use the grommet (TPU printed part) to make a stencil for the holes in the box (PUT THE HOLES AS HIGH AS YOU CAN, OR I T WILL MELT ROOLS WITH DIRECT HEAT) I should have drilled the corners and then used a sharp exacto knife to score several times but I used a dremel. Use what works for you!!. After you print everything and put the 4MM threaded inserts in, you will see how it goes together. The 40MM bolts go in the 4 center holes and the other 4MM, 50MM bolts go in the outer holes. The PC spacer goes in between the TPU/PC grommet and heater. The heater and thermostat all just plug in. I moved the thermostat sensor around and found that the bottom right (or left) 2-3 inches up the side of the box is the most accurate. If you put it in the middle it gets more direct heat from the fan and is not as accurate, (See pic). MAKE SURE THE FAN IS BLOWING TOWARDS THE DESSICANT INSIDE THE 90-Degree DUCT (see below). I added an inside and outside temp/humidity sensor (see pic) but you don't need it. If you want to add temperate resistant silicone to the bottom of the heater core and the place where you drill a hole for the temp sensor, go for it, I did. I also strongly suggest printing a large desiccant holder and adding that to the inside to help catch humidity. Here is one I used, Please message me if you have any questions! And thanks in advance for making one!

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1. TPU (Amazon)
2. PC (Amazon)
3. PETG (Amazon)
4. 8 4M Threaded Inserts (Amazon)
5. 4 40MM Bolts (Amazon)
6. 4 50MM Bolts (Amazon)
7. 8 4M Washers (Amazon)
8. 3 3M 8mm Bolts (Amazon)
9. Sealed Box (Amazon) You can buy just one from Home Depot or Costco ETC.. Or use one you have already 44QT to 55QT
10. Heater with Fan Plug and Play (Amazon)
11. Thermostat plug and play (Amazon)
12. External and internal temperature and humidity gauge (not needed but nice to have) (Amazon)