German GMN bearings GMN models GMN prices

GMN bearings are bearings that operate under sliding friction. Plain bearings operate smoothly, reliably, and without noise. Under liquid lubrication conditions, the sliding surfaces are separated by lubricating oil without direct contact, which can greatly reduce friction loss and surface wear; the oil film also has a certain vibration absorption capacity. However, the starting friction resistance is relatively high. The part of the shaft supported by the bearing is called the journal, and the part mating with the journal is called the bearing bush. The anti-friction material layer cast on the inner surface of the bearing bush to improve its friction properties is called the bearing lining. The materials of the bearing bush and bearing lining are collectively referred to as plain bearing materials. Plain bearings are generally used in high-speed and light-load operating conditions.

GMN bearing classification

There are many types of plain bearings: 1) According to the direction of load they can withstand, they can be divided into radial (centripetal) plain bearings and thrust (axial) plain bearings. 2) According to the type of lubricant, they can be divided into oil-lubricated bearings, grease-lubricated bearings, water-lubricated bearings, gas bearings, solid lubricated bearings, magnetic fluid bearings, and electromagnetic bearings, totaling 7 categories. 3) According to the thickness of the lubricating film, they can be divided into thin-film lubricated bearings and thick-film lubricated bearings. 4) According to the bearing bush material, they can be divided into bronze bearings, cast iron bearings, plastic bearings, jewel bearings, powder metallurgy bearings, self-lubricating bearings, and oil-impregnated bearings. 5) According to the bearing bush structure, they can be divided into circular bearings, elliptical bearings, three-lobe bearings, step-face bearings, tilting-pad bearings, and foil bearings. Bearing bushes are divided into split and integral structures. To improve the friction properties of the bearing bush surface, one or two layers of anti-friction material are often cast on the inner diameter surface, usually called the bearing lining, so there are bimetallic and trimetallic bearing bushes. The bearing bush or bearing lining is an important component of plain bearings, and the materials of the bearing bush and bearing lining are collectively referred to as bearing materials. Since the bearing bush or bearing lining is in direct contact with the journal, the journal part is generally more wear-resistant, so the main failure mode of the bearing bush is wear. The wear of the bearing bush is directly related to the journal material, the bearing bush material itself, the lubricant, and the lubrication state. These factors should be comprehensively considered when selecting bearing bush materials to improve the service life and working performance of plain bearings.

GMN bearing grease selection

1) When the bearing load is heavy and the speed is low, grease with small penetration should be selected; conversely, grease with large penetration should be selected. For high-speed bearings, select grease with smaller penetration and good mechanical stability. Special attention should be paid to ensuring that the viscosity of the base oil of the grease is lower. 2) The dropping point of the selected grease is generally 20-30℃ higher than the operating temperature. In the case of continuous operation at high temperatures, care should be taken not to exceed the allowable use temperature range of the grease. 3) When plain bearings operate in water-splashed or humid environments, calcium-based, aluminum-based, or lithium-based greases with good water resistance should be selected. 4) Select grease with good adhesion. Selection of grease for plain bearings: Load<1MPa, journal circumferential speed below 1m/s, maximum operating temperature 75℃, select No. 3 calcium-based grease; load 1-6.5MPa, journal circumferential speed 0.5-5m/s, maximum operating temperature 55℃, select No. 2 calcium-based grease; load >6.5MPa, journal circumferential speed below 0.5m/s, maximum operating temperature 75℃, select No. 3 calcium-based grease; load<6.5MPa, journal circumferential speed 0.5-5m/s, maximum operating temperature 120℃, select No. 2 lithium-based grease; load >6.5MPa, journal circumferential speed below 0.5m/s, maximum operating temperature 110℃, select No. 2 calcium-sodium based grease; load 1-6.5MPa, journal circumferential speed below 1m/s, maximum operating temperature 50-100℃, select No. 2 lithium-based grease; load >5MPa, journal circumferential speed 0.5m/s, maximum operating temperature 60℃, select No. 2 calendering grease; in humid environments, at temperatures of 75-120℃, calcium-sodium based grease should be considered. In humid environments, if the operating temperature is below 75℃ and No. 3 calcium-based grease is not available, aluminum-based grease can be used. When the operating temperature is 110-120℃, lithium-based or barium-based grease can be used. For centralized lubrication, the consistency should be lower. Lubrication cycle for plain bearings with grease: Occasional operation, unimportant parts: Shaft speed<200r/min, lubrication cycle once every 5 days; shaft speed >200r/min, lubrication cycle once every 3 days. Intermittent operation: Shaft speed<200r/min, lubrication cycle once every 2 days; shaft speed >200r/min, lubrication cycle once every 1 days. Continuous operation, operating temperature less than 40℃: Shaft speed<200r/min, lubrication cycle once every 1 days; shaft speed >200r/min, lubrication cycle once per shift. Continuous operation, operating temperature 40-100℃: Shaft speed<200r/min, lubrication cycle once per shift; shaft speed >200r/min, lubrication cycle twice per shift. It is necessary to ensure uniform and close contact between the journal and the plain bearing, while maintaining a certain clearance fit. This refers to the central angle subtended by the contact surface between the journal and the plain bearing. The contact angle should neither be too large nor too small. A contact angle that is too small will increase the pressure on the plain bearing, potentially causing significant deformation, accelerating wear, and shortening service life; a contact angle that is too large will affect the formation of the oil film, preventing effective liquid lubrication. Experimental research shows that the limit of the plain bearing contact angle is 120°. When the plain bearing wears to this contact angle, liquid lubrication will break down. Therefore, under the premise of not affecting the pressure conditions of the plain bearing, the smaller the contact angle, the better. From the theoretical analysis of friction torque, when the contact angle is 60°, the friction torque is minimal. Therefore, it is recommended that for plain bearings with speeds higher than 500r/min, the contact angle should be 60°; for plain bearings with speeds lower than 500r/min, the contact angle can be 90°, or 60°.

GMN bearing usage precautions

Plain bearings involve surface contact, so a certain oil film must be maintained between the contact surfaces. Therefore, the following issues should be noted during design: 1) Ensure that the oil film can smoothly enter the friction surface. 2) Oil should enter the bearing from the non-load-bearing area. 3) Do not open a full-circle oil groove in the middle of the bearing. 4) For split bearings, open oil grooves at the joints. 5) Ensure that the oil ring provides sufficient and reliable lubrication. 6) Do not block the oil filling holes. 7) Do not form stagnant oil zones. 8) Prevent sharp edges and corners that could cut the oil film. Plain bearings can also be lubricated with grease. When selecting grease, consider the following points: 1) When the bearing load is heavy and the speed is low, grease with small penetration should be selected; conversely, grease with large penetration should be selected. For high-speed bearings, select grease with smaller penetration and good mechanical stability. Special attention should be paid to ensuring that the viscosity of the base oil of the grease is lower. 2) The dropping point of the selected grease is generally 20-30℃ higher than the operating temperature. In the case of continuous operation at high temperatures, care should be taken not to exceed the allowable use temperature range of the grease. 3) When plain bearings operate in water-splashed or humid environments, calcium-based, aluminum-based, or lithium-based greases with good water resistance should be selected. 4) Select grease with good adhesion.

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