Elegoo Centauri Carbon Fan Recirculation Mod - *Major* Noise Reduction (no muffler)

First I have to give credit to Synthetic Electron 3D for the original concept and design.  He really did most of the work!

This mod re-uses the stock 'auxiliary' cooling fan, blowing through the flat horizontal blower in the rear of the printer, to convert it from ambient-air intake to a recirculating fan.  This makes the printer FAR less noisy, as this fan is the main culprit in the incredible loudness of this otherwise awesome printer.  It also improves usability of the printer's enclosed chamber, by no longer pulling in cool outside air. 

I believe* this mod takes less filament than many of the ‘muffler’ designs while having more of an impact on noise, due to actually removing/redirecting the noisy fan into the enclosed chamber, rather than adding a large muffler which inhibits airflow and adds mechanical stress to the stock fan (making it push harder and become inherently louder).  This also doesn't add to the size of the machine, and clearly looks a lot better 😉

* I haven't tested either the filament or noise theory, comparing the more common externally mounted printed mufflers - please comment with the results if you do!

Parts needed:

- M2 self-tapping screws: https://amzn.to/4eV5vLx (only using the 6mm long ones)

-  (1x) fan cable extension: https://www.amazon.com/dp/B0C5RFJSYM

- (1x) magnetic cable tie (just the base): https://www.amazon.com/dp/B0DP9ZZFBW

- (1x) m4 x 25mm socket head screw or button head screw (round head)

- (1x) m4 nut

Recommended print settings:

- PETG or ASA (or maybe High-Temp PLA)

- 4 walls (if 0.20mm nozzle), 3 walls (if 0.6mm nozzle)

- 0.24 layer height (if 0.20mm nozzle), 0.36 layer height  (if 0.6mm nozzle)

- 25% infill

- Use manually-added supports at the 2 features I point out in the pics.

- The mounting hole/flange at the far bottom, to mount the blower fan, is at (I think) a 45deg angle - with PETG this printed badly for me, might be worth using supports here, too.

I used PETG with a 0.6mm nozzle. Total time in Orca was 8.5 hours, total filament was 234g.

Installation notes:

- Check clearance to your drive belts from the little baffles - mine fit great but mileage may vary. They can easily be trimmed with snips. If it looks concerning, just trim them off - not a good risk-to-reward ratio there 😉

-  To seal up the outer case from the unused fan holes, I just used blue painters tape over the back 🩹.  A cover could be designed and printed, but for something I'd never see, 10 seconds and some tape fit the bill.

Bed Cable:

After seeing reviews on the original post concerned about the bed cables, I decided to shift the entire vertical fan duct closer to the bed. This way the cables can fit behind it.  After printing, I was glad to see it worked great 95% of the time, but when the bed went low enough and back up, the bed cable could snag on the fan corner and/or printed duct corner.

After trying and failing to reroute the bed cable to avoid snags, I tested another solution, which works perfectly but requires a purchase:   https://www.amazon.com/dp/B0DP9ZZFBW

I keep these on hand for hanging things around my garage, and frequently replace the cable mount (held in with m4 screw) with a long m4 screw + jam-nut, to create a long hanger for safety glasses, headlamps, etc. The magnets are considerably strong, and have a rubberized coating that works well to prevent sliding.

Taking one of these jigs and sticking it to the rear 3d printer panel, I positioned it where it would act as a cable-guide to prevent the bed cable from snagging on anything. I did some testing at different positions, but the location shown in the images seemed most reliable and cable-friendly.

Ideas for future remixers:

- To avoid purchasing the magnets, an option may be to simply add the bed-cable guide feature into the fan-duct print at the same location as my magnetic bolt. 

- I extended my fan cable but didn't find a good spot to stuff the little red control board. With some mounting provisions and cable planning it could fit behind the 'cross-wall' and be hidden and secure.


Happy printing!
- Casey