Elegoo Centauri Carbon Double Muffler w/ Air Recirculation

-Added a version with a 5.5mm deeper filter compartment in order to add active carbon filters

-Added seals holder

-Added two 'less supports' versions with the middle strip removed, the filters are supported by a thicker lip. Many thanks to zx4133 for the idea!

-Capitalized on zx4133 idea and added another two versions that need very minimal or no supports, the frame around the filters is supported by a hex wall. It's possible to use automatic tree supports with "Ignore small overhangs" enabled, only the holes and threads will be supported
 Please note: the hex wall can cause a lot of stringing, I suggest printing the 'less supports thanks zx4133' version.

In this muffler it's possible to open/close the air passage between the aux and case fan chambers and to close their intake/outtake individually.

This allows the muffler to be used in two configurations:

• "Normal":  both fans will work as usual, just quieter

• Recirculation: The air pulled from the printer by the case fan will be sent directly back inside by the aux fan.

The recirculation can be helpful in keeping the chamber temperature while still being able to achieve air filtration through the HEPA filters, I tried a couple of prints in ASA and while of course it's not 100% filtered (nor am I saying this is an alternative to venting directly outside), the smell was immensely reduced compared to printing with fans off.

Needs 10x3 magnets and two drops of super glue.
For the assembly:

• Set the flap inside the muffler with the two chamfered corners facing down, drop of super glue on the 'rod' and push it in from the outside.

• Wait for the glue to dry, push the stopper through the rod until it's flush with the outer shell.

• Another drop of super glue on the part of the rod that'll be sticking out, push the knob in place (@people from the UK: no innuendos here, keep the super glue where it belongs)

I suggest printing with no less than 3 walls and 5 bottom layers, it's also an option to print in PETG so that the last few layers can be printed in TPU for an integrated gasket, in this case I'd also print the two 'seals' and the stopper in TPU after, since it would be already loaded in the printer.

Use tree supports for the muffler. I also made a version that requires less support but I printed the 'normal' one to make sure there were no issues. In my opinion that extra wall shouldn't impact airflow but again, I haven't tried it personally.

Some data about noise:

This isn't scientifically accurate in the slightest, I used an app on my smartphone to measure the noise, the aux fan is set at 50%.

Measured next to the printer's power switch:

• Case fan no muffler: 64db

• Aux fan no muffler: 72db

• Case + aux no muffler: 74db

• Case fan + OG muffler: 60db

• Case fan + aux OG muffler: 73db

• Case fan + double muffler: 60db

• Aux fan + double muffler: 67db

• Case + aux double muffler: 69db

• Case + aux in recirculation: 63db

Measured about 1.5m away:

• Case fan no muffler: 50db

• Aux fan no muffler: 57db

• Case + aux no muffler: 61db

• Case fan + OG muffler: 46db

• Case fan + aux OG muffler: 58db

• Case fan + double muffler: 46db

• Aux fan + double muffler: 53db

• Case + aux double muffler: 54db

• Case + aux in recirculation: 50db

P.S. In my opinion, the easiest way to have proper recirculation with the material that need it the most like ASA and Nylon, is to just change the material type in the slicer to another that likes high temperatures but still gets the case fan forced on in the slicer, like PETG