One of the first mods I made to the N4M is adding X and Y locks which help keep the correct tension on pulleys. They some times do them to loosen after normal use.
You can find the X and Y locks I used here by SebastianRubner
https://www.thingiverse.com/thing:6130503/files
The next upgrade I recommend is to new shroud + new fans that reduces dramatically the fan noise on the stock extruder. The one I used was designed by Orzorzorz. This has made a big difference in noise as I have the printer next to my desk at the moment and when the stock fans turns on, it sounds like a window turbine. It is so much quieter now. This is a must, IMO.
https://www.printables.com/model/711424
For quiter and smoother movement I switch to linear rails provided by tbstrong3d which can be found here.
For vibration I installed dampers designed by Digitale Lehrerin which can be found at the link below and has worked great.
Leave a Reply