Baffle-ing - A single purpose noise reduction exhaust system

What 

I made this to fit on the back of a broken Subzero 424 wine fridge that I use as a printer enclosure to reduce sound.

The problem with putting a 3D printer in a fridge is all the extra insulation means it's hotter than PLA likes, so to cool things down I cut some holes in the back and mounted 80mm noctua fans with controlled by this system: https://www.makergadgets.org/diy/p/smart-exhaust. When the temp in the enclosure goes over 33C (~91F) the fans cut on. One pulls fresh air in to the bottom. The other pushes hot air out. Temperature problem solved!

The problem is: Cutting giant holes in an enclosure lets a lot of sound out. So I had to mitigate that somehow. I looked up designs on youtube and found people making enclosures for generators or shop vacs. In general the principal is to make a bunch of 90 degree turns and to have some material to soften/dampen the sound (otherwise you just made a musical instrument instead of an exhaust baffle).

Materials - Per unit (two units needed for exhaust and intake)

• Fasteners
  • M4x20mm screws and washers - Fourteen (14)
  • M4x10 heat inserts - Fourteen (14)
• Sound materials
  • First layer: Butyl mat (tons out there but I used [Noico from Amazon ](https://www.amazon.com/dp/B01KZ5X7KO). The foil helps block the sound going through and reflects it, the butyl is gummy and isolates the foil. It also stops vibrations from propagating/ringing in the print body. It absorbs some, but not much.
  • Second layer: [Hybrid mat from Siless]( https://www.amazon.com/dp/B0B6JKF9SC ). This acts to block and to absorb sound, but it doesn't really “deaden” or stop sound propagating in the print body (as I understand it). 
  • Third layer: Polyethlene foam ([siless foam liner](https://www.amazon.com/Sound-Deadening-Foam-157mil-Insulation/dp/B07B75PD8B/ref=sr_1_1_sspa). This doesn't block at all, instead it absorbs some of the energy to so it echos less. The baffle is basically designed to be an echo chamber, so by removing echo energy we reduce the overall sound coming out.

I didn't have those materials on hand when I designed it, so the design accidentally restricts airflow more than I had planned. Overall though, it keeps my interior under 45C when printing PETG and under 40C when printing PLA. I didn't feel the need to do another revision.

As a word of warning, these materials have a maximum temperature rating. They're maxed out at around 200F or 93.33C. The exhaust should never see that but also I don't print anything hotter than PETG on this thing.

Assembly - per unit (two total needed)

• Print a front, back and two "tops"
• Use a solder iron to insert seven M4x10mm inserts
• Install butyl mat, combo mat, and foam layer
• Put it all together with fourteen M4x20mm screws and washers

Install

To install the units you'll have to disassemble them (otherwise you can't access the sheet metal screw holes).

• I put some of the “hybrid mat” on the back of the unit where it touches the fridge (and cut some holes in the mat where needed). 
• Install the top with screws to the back panel
• I then used some 1.5" sheet metal screws to fix the back onto the fridge. Don't torque too much or it will make the panel arch.
• Attach the front panel to the bottom panel with screws - A this point you have two pieces instead of four
• Attach the two pieces together via screws in the top and bottom

When tightening the screws  make sure to do them gradually and evenly. Also tool access is an issue. GLHF