I started a long 3D print today. Initially it was doing fine. Then I started hearing a loud squeak, yikes! I just lubed the smooth rods 2 days ago so all I could think was a bearing was shot. Went over to the printer and put my ear down near the bed trying to locate which bearing was squealing and couldn’t.
I finally looked up and realized it was the filament spool as it rotated on the holder. Squeal depends on speed and angle to the print head. Whew! Gonna have to come up with a fix.