Lubricants

Lubricants

Lubricants have the task of forming an adequate lubricating film that separates the elements of a roller bearing that roll or slide on one another from one another, consequently preventing direct metallic contact. The greases* used in the Nanotec stepper motors and servomotors have a high consistency, adhere well in addition to offering excellent protection against contamination and corrosion and with the sealed ZZ bearings, have a long grease usage of approx. 30,000 h. Considerably higher operating hours can be achieved under certain application conditions with specified high-performance greases. They are selected according to the type and size of the bearing, the type of load such as vibration and shock load, the speed range, the shaft alignment, the material quality, the sealing as well as the ambient conditions such as humidity, vibration, vacuum, air draft and contamination.

Greases

Lubricating greases consist of different variations of earth oils, thickeners and special additives that are added to the grease to improve certain features such as oxidation resistance, corrosion and wear protection. For example, the thickeners decisively influence the drop point, the working stability, the behavior towards humidity and fluids, the oil separation, the conveying operation and stability during storage. Greases that are soft at higher temperatures (low consistency) can emerge from the bearing point and greases that are too stiff (high consistency) at low temperatures can obstruct the smooth rolling of the rolling elements, for example.

Consistency can be understood as the characteristic of the lubricating grease to oppose the deformation through externally acting forces by an internal resistor. The drop point gives the temperature at which the lubricating grease loses its consistency and becomes fluid. Optimum lubrication is, therefore, only ensured in the defined temperature application field. Prolonged exceeding or undercutting of the temperature thresholds can lead to premature failure of the bearing. The deciding factors are the temperature limit values at which the lubricating grease exhausts its full lubricating performance and service life potential. The grease ages and oxidizes more quickly above the recommended limit value for the max. working temperature, releases too much oil and subsequently only reaches short lubricating intervals or grease usage steady-state values. Below the recommended limit value the lubricating grease releases less and less oil which means adequate lubrication of the roller bearing is no longer ensured and, hence, deficient lubrication states can lead very quickly to the failure of a bearing.

Applications

Different applications such as oscillating movements with a restricted rotation angle range < 90° during continuous running (the balls no longer carry out whole revolutions of 360° and have, therefore, to be provided with a special grease), the use of special lubricants at low or high temperatures or also food-grade special lubricants require detailed knowledge of tribological requirements.
By contrast, momentary operation, e.g. on start-up, is innocuous as the frictional heat generated raises the bearing temperature into the green operating temperature range. To achieve a running friction that is as low as possible, an operating life that is as long as possible and a speed that is as high as possible, a grease distribution and run-in must be carried out. This helps to reduce the initially occurring higher friction from flexing and can have a positively effect on the operating time as well as the speed capacity. We will test this and incoorporate this in the design according to your applications.