German VAI bearings, VAI models, VAI prices

VAI bearings are precision mechanical components that convert sliding friction between the rotating shaft and the bearing housing into rolling friction, thereby reducing frictional losses. Rolling bearings generally consist of four parts: inner ring, outer ring, rolling elements, and cage. The inner ring fits with the shaft and rotates with it; the outer ring fits with the bearing housing to provide support; the rolling elements are evenly distributed between the inner and outer rings by the cage, and their shape, size, and quantity directly affect the performance and service life of the rolling bearing; the cage ensures uniform distribution of the rolling elements, guides the rolling elements in rotation, and provides lubrication.

VAI bearing features and structure

Common sliding bearing materials include bearing alloys (also known as Babbitt metal or white metal), wear-resistant cast iron, copper-based and aluminum-based alloys, powder metallurgy materials, plastics, rubber, hardwood, and carbon-graphite, polytetrafluoroethylene (Teflon, PTFE), modified polyoxymethylene (POM), etc. Sliding bearings absorb and transmit forces between relatively moving parts, maintaining the position and positioning accuracy of the two parts. Additionally, they convert directional motion into rotational motion (such as in reciprocating piston engines). Sliding friction occurs during the operation of sliding bearings; the magnitude of sliding friction mainly depends on manufacturing precision, while the friction force of a sliding bearing mainly depends on the material of the bearing sliding surface. The working surfaces of sliding bearings generally have self-lubricating functions; sliding bearings are classified into non-metallic sliding bearings and metallic sliding bearings based on material. Non-metallic sliding bearings are primarily plastic bearings, which are generally made from high-performance engineering plastics. Professional manufacturers typically possess self-lubricating modification technology for engineering plastics, enhancing them with fibers, special lubricants, glass beads, etc., to achieve specific performance levels, and then processing the modified plastics into self-lubricating plastic bearings via injection molding. In the early twenty-first century, the most widely used metallic sliding bearings were three-layer composite bearings. These bearings generally use carbon steel plates as the substrate, sinter a layer of spherical copper powder onto the steel plate using sintering technology, and then sinter a layer of PTFE lubricant approximately 0.03mm thick onto the copper powder layer. The intermediate layer of spherical copper powder primarily serves to enhance the bonding strength between the steel plate and PTFE, while also providing certain load-bearing and lubricating functions during operation.

VAI bearing materials

1) Metallic materials, such as bearing alloys, bronze, aluminum-based alloys, zinc-based alloys, etc. Bearing alloys: Also known as white metals, bearing alloys are primarily alloys of tin, lead, antimony, or other metals. Due to their good wear resistance, high plasticity, good conformability, good thermal conductivity, good anti-seizure properties, and good oil adsorption, they are suitable for heavy-load and high-speed conditions. Bearing alloys have low strength and are relatively expensive; they must be cast onto bronze, steel strips, or cast iron bearing shells to form a thin coating. 2) Porous metallic materials (powder metallurgy materials): Porous metals are powder materials with a porous structure. If immersed in lubricating oil so that the micropores are filled with oil, they become oil-impregnated bearings with self-lubricating properties. Porous metallic materials have low toughness and are only suitable for stable, non-shock loads and medium to low speeds. 3) Non-metallic bearing plastics: Common bearing plastics include phenolic plastics, nylon, and polytetrafluoroethylene. Plastic bearings have high compressive strength and wear resistance, can be lubricated with oil and water, and also have self-lubricating properties, but they have poor thermal conductivity.

VAI bearing maintenance

During operation, plain bearings generate friction due to contact between the journal and the bearing shell, leading to surface heating, wear, and even seizure. Therefore, when designing bearings, bearing shell materials with good anti-friction properties should be selected, appropriate lubricants and supply methods should be used, and the bearing structure should be improved to achieve thick-film lubrication. Shell surface corrosion: Spectral analysis reveals abnormal concentrations of non-ferrous metal elements; many sub-micron wear particles of non-ferrous metal components appear in the spectrum; lubricating oil has excessive moisture and acid value. Journal surface corrosion: Spectral analysis reveals abnormal iron element concentrations; many sub-micron iron-component particles appear in the ferrogram; lubricating oil has excessive moisture or acid value. Journal surface scoring: The ferrogram contains iron-based cutting wear particles or black oxide particles, and temper colors are present on the metal surface. Shell back fretting wear: Spectral analysis reveals abnormal iron concentrations; many sub-micron iron-component wear particles appear in the ferrogram; lubricating oil moisture and acid values are abnormal. Bearing surface scoring: Cutting wear particles are found in the ferrogram, with non-ferrous metal composition. Shell surface spalling: Many large-sized fatigue spalling alloy wear particles and layered wear particles are found in the ferrogram. Bearing burn-out: Many large-sized alloy wear particles and black metal oxides are present in the ferrogram. Bearing wear: Due to the metal characteristics of the shaft (high hardness, poor compliance), adhesive wear, abrasive wear, fatigue wear, and fretting wear are likely to occur. Prevention of paint rust: Paint rust is characterized by sealed motors sounding normal initially, but becoming very noisy after a period of storage, with severe bearing rust upon removal. Many manufacturers consider this a pre-bearing issue; the main problem is that insulating varnish volatilizes acids at certain temperatures and humidity, forming corrosive substances that cause corrosion damage to plain bearings. Plain bearing service life is closely related to manufacturing, assembly, and usage; every link must be optimized to ensure the best bearing operation and extend service life. 1) During the production of coating machine bearings, rust prevention and oil-seal packaging requirements were not strictly followed for processing parts and assembled finished products. For example, rings had excessively long turnover times, and outer ring outer surfaces contacted corrosive liquids or gases. 2) The quality of anti-rust lubricants and cleaning kerosene used in production did not meet technical process specifications. 3) Due to the continuous price drop of coating machine bearing steel, the material quality gradually declined. For instance, high content of non-metallic impurities in steel (increased sulfur content reduces inherent rust resistance) and metallographic structure deviations. Current manufacturers source coating machine bearing steel from various suppliers, resulting in mixed steel quality. 4) Poor environmental conditions, high content of harmful substances in the air, and small turnover areas make effective rust prevention difficult. Additionally, hot weather and workers violating rust prevention protocols are not uncommon. 5) Packaging materials for coating machine plain bearings, such as rust-proof paper, nylon paper (bags), and plastic tubes, do not meet the oil-seal rust prevention packaging requirements for rolling coating machine bearings, contributing to rust. 6) Insufficient turning and grinding allowances for coating machine plain bearing rings, and incomplete removal of oxide scale and decarburized layers on the outer surfaces, are also contributing factors.

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