A small, 3 inch by 6 inch sign to help you remember to replace one of the more overlooked and troublesome parts of any 3D printer!

I made this after the second time the bearings in my extruder failed from use, because I frequently overlook them when diagnosing an extrusion issue. Given the life expectancy of 300 to 500 hours on these little bearings, it doesn't take long before they wear out and start causing havok with your prints.
Signs of a worn extruder bearing:
Occasional thumps or clicks from the extruder when operating,
Serious under-extrusion during print cycles (may extrude normally at slow speeds)
Difficulty inserting filament into the extruder
Tactile feel of bumps or roughness when rotating the bearing by hand
Grinding, binding, or otherwise impeded ease of rotation

If you are curious, the bearings are 4x8x3mm MR84ZZ Deep groove bearings with double metal seals, and are recommended to be ABEC-7 or better for longevity. For ease of purchase, you can get these from Bondtech for about 1.15 per bearing, and they are manufactured specifically for the 3D printing environment.

BE CAREFUL WITH YOUR BEARINGS! There is another similar one, a 684ZZ bearing, that measures 4x9x4mm. Use this one for Creality K1 Max printers, as the 4x8x3 will fall all the way through the extruder gears. Unfortunately, these are not sold by bondtech, and I had to source them from amazon.