If you have had your printer for a while you may find that the linear bearings have become dry. The linear bearings are the 'tracks' that the respective axes travel along when constructing your model. Dry bearings can cause the machine to become quite noisy, especially when printing on 'Fast'.
To remedy this, you will need either lithium or silicone grease. We prefer to use an aerosol type, as we can spray lightly over the bearings without needing to remove the panels to access the bearings.
Be sure to turn the printer off before lubricating the bearings and to wipe any excess grease away.