Lubricant selection FAG machine tool spindle bearings can be lubricated with grease or oil. Machine tool applications require longer cycle times and higher speeds. However, oil lubrication must be able to dissipate heat in any case. Lubricants are often mineral base oils. Mineral oils must meet the requirements of DIN 51517, see table. Special lubricants, such as synthetic oils, are only used under extreme conditions. Under special working conditions, lubricating oil has special requirements. For example, temperature and radiation. The effectiveness of rolling bearing additives has been demonstrated by lubricant manufacturers, see table. For example, anti-wear additives are particularly important for rolling bearings in a state of mixed friction. Base oils and their typical properties 1) Most of the base oil types used, natural and pollution-free as the product is a natural product. 2) Widely used types of synthetic oils, including lubricants approved for use in the food industry. Lubricant Additives and Actions Base Oil, Abbreviation Operating Temperature Viscosity / Temperature Performance and Synthetic Rubber Compatibility Price max. min.C CMineral oil1), Min +120 20 1001Polyalphaolefin2),PAO, SHC+150 40 160 Good 6 Additive Type Function Extreme Pressure Additive EP ■ Improves pressure absorption performance ■ Forms a reactive layer that reduces wear Friction Modifier FM ■ Improves frictional conditions under mixed and boundary friction conditions Wear protection AW ■ Reduces adhesive and abrasive wear corrosion inhibitors under mixed friction KI ■ Prevents rust on metal surface and anti-aging agent OI ■ Delays lubricant oxidation and adhesion Additives ■ Improves the viscosity of lubricants to the surface Detergent and dispersant ■ Enhances pollutant separation and lubricant transparency Viscosity-temperature property improver ■ Increases (decreases) viscosity/temperature characteristics Foam inhibitor ■ Prevents stable foam formation Pour point depressant ■ Reduces pour point. Lubricating oil viscosity is recommended to increase life and safety by increasing the thickness of the lubricating oil film that divides the contact surfaces. Since the thickness of the lubricating oil film increases with the viscosity of the lubricating oil, a lubricating oil with a high operating viscosity should be selected when possible. . If the ratio of kinematic viscosity to reference viscosity satisfies u003d 1 2, the bearing can achieve a very long life. However, the friction of the lubricant also increases with increasing viscosity. At low and normal temperatures, oil supply and drain may be problematic. On the one hand, the viscosity of the lubricating oil should be selected to be sufficiently high, but, on the other hand, the energy losses due to the increase in friction should be as small as possible. It must be ensured that the bearings are adequately lubricated under all conditions. Operating Viscosity In individual cases, the preferred operating viscosity cannot be achieved for the following reasons: ■ Restricted by other components on the machine, a thinner lubricant film is required. ■ Circulating oil lubrication should use lubricating oil with good fluidity, in order to dissipate heat and discharge pollutants. ■ Although the required operating viscosity can be achieved with most lubricants. However, in some cases, such as high temperature or very low ambient viscosity, the operating viscosity will be lower than required. In this case, a lower viscosity lubricating oil can be selected. Lubricants must contain effective additives and their suitability must be verified by bearing testing. Based on the deviation from normal values, a reduction in fatigue life and wear on functional surfaces can be predicted and can also be determined by calculating the achievable RHP bearing life. For ISO and SAE compliant common viscosity lubricants, see page 20, Figure 1 and page 20, table. Lubricant Selection Lubricants are selected based on the specific application. In most cases, the oil used is gearbox or hydraulic oil CLP or HLP, viscosity grade ISO VG 46, ISO VG 68 or ISO VG 100. Determine oil viscosity from speed and load factor C/P. High speed parameters At high speeds, lubricants with antioxidants and low foaming tendency and appropriate viscosity-temperature characteristics are preferred. The maximum allowable speed parameter for cylindrical roller bearings is n dM u003d 250 000 min1 mm, and for thrust deep groove ball bearings is n dM u003d 440 000 min1 mm. Suitable synthetic oils that exhibit good viscosity-temperature properties are esters and hydrogenated polydecene PAOs, as these oils show little viscosity decrease with increasing temperature. In the start-up stage, the temperature is relatively low, which can avoid the temperature rise caused by the high splash loss. Once the higher equilibrium temperature is reached, the viscosity of the lubricating oil can still meet the lubrication requirements. Heavy loads If the FAFNIR bearing is heavily loaded (C/P 7) or the kinematic viscosity is lower than the reference viscosity 1, a lubricant with antiwear agent (code P according to DIN 51502) must be used. Antiwear agents reduce the detrimental effects of damage to metal contacts. The suitability of these antiwear additives varies and is greatly affected by temperature. Their effect can only be evaluated by rolling bearing tests (eg on the test bench FE8).