Hey guys, Just sharing what I did to finally reduce the fan noise to acceptable level. My printer is 3D R1 Plus. 1. Bottom plate fan. Simply replace it with Noctua 40mmx10mm fan ($16). One additional benefit is Noctua fan come with longer cable and one additional adapter cable. Originally I have to struggle with plugging in the very short fan cable to the difficult to see circuit board while holding on to the bottom plate and torch light. Now I just leave the adapter section to the circuit board and plug/unplug the connector between the fan cable and adapter cable. 2. Replace the power supply with Mean Well 350W power supply ($51). The stock power supply has no auto fan control so the fan is on all the time. Mean Well supply only turn on when printer is consuming a lot of power. I took a look at the Kill-A-Watt to see power consumption. When the printer is on but idle, 12 Watt, the hot end about 35W, and the heated bed 120W. So the PSU fan will turn on during printing but not before and after cool down. I replace the power supply instead of just the fan because I think Mean Well's power is better quality (better over load/short circuit protection etc). The PSU's fan can be replaced by Noctua 60x25 fan ($13.25) to further reduce the fan noise but at this stage doesn't feel the need to do so. I might change in the future though. 3. Replace the 25mm hot end fan. I tried several 25mm fan that claimed to be quiet. They are quieter than the stock fan but one break the second day, and the other emit a high pitch screeching sound. These little fan are meant for Raspberry Pi, I believe, and may not be suitable for 3D printer's radical movement. So I printed an adapter that uses 40mm Noctua fan. I've upload the design on thingiverse if anyone is interested in doing the same. (Search 40mm to 25mm fan adapter for ROBO 3D) After all these changes, my Robo now when turn on is as quiet as my laptop (when the laptop fan is on). During printing, there will be additional gear, bed movement, vibration sound plus the PSU fan but the whole setup is much quieter than stock and at least I won't have to shout over printer to carry on a conversation. Hopfully my experience can be of some help to whoever want to silence the printer. Mod On!