The x-beam carriage rail requires lubrication every 20,000,000 revolutions of the z-shaft. Use only multi-purpose (lithium) grease to lubricate the carriage rails.
Lubrication Procedure:
Move the x-beam all the way forward (press and hold 
, then press 
), and all the way to one side (press and hold , then press 
or 
).
Using a clean cotton rag, wipe off any dust/lint accumulation from both of the carriage rails (see the image below for the location of these rails).
Again using a cotton rag, apply a very thin layer of multi-purpose lithium grease to both carriage rails (one in the front and one in the back of the beam) from underneath the beam. If you can see clumps of the white grease after you have applied it, then you have put too much. Wipe off excess grease before proceeding.
Move the beam all the way to the other side (press and hold , then press or ) and repeat step 2 on the other end of the carriage rails.
