The CNC system y axis armas have two bearing each. With use the bearing can wear and will need to be replaced. You might see a bearing ball loose which is a sign that the bearing needs replacing. Each side has two bearings and we recomend that when you need to replace the bearing on one side you replace them on the other side as well.
It is possible to lubricate bearings useing the lubrication nib on the inside of the bearing. That will take quite some time to do.
This video shows the proceedure for replacing the bearing on the CNC AutoBlaster.