Elegir lo correcto cojinete de giro is crucial for the efficient and safe operation of machinery. It involves a detailed analysis of the application’s requirements and the operating environment.
How to choose a slewing bearing
1. Understand Load Requirements
Slewing bearings are designed to handle complex load combinations. You need to accurately determine all the loads acting on the bearing:
Axial Load (Fa): The vertical force acting along the axis of rotation.
Radial Load (Fr): The horizontal force acting perpendicular to the axis of rotation.
Tilting Moment (M): The force that tries to tip the bearing over. This is often the determining factor for slewing ring selection. It’s a product of a force and its distance from the bearing’s axis of rotation.
It’s essential to consider both static (at rest) and dynamic (during operation, including impact and shock loads) maximum loads. Manufacturers often provide “static limiting load diagrams” to help estimate the required bearing size based on axial load and tilting moment.
2. Consider Bearing Type
Different slewing bearing types are suited for various load capacities and performance characteristics:
Four-Point Contact Ball Slewing Bearings:
Characteristics: Compact structure, peso ligero, four-point contact between balls and raceway. Can bear axial, radial, and tilting moment loads simultaneously. Good for low to medium speeds.
Aplicaciones: Small to medium-sized cranes, excavadoras, welding operators, slew conveyors.
Crossed Cylindrical Roller Slewing Bearings:
Characteristics: Rollers arranged in a 1:1 cross pattern. Offer high manufacturing precision, estructura compacta, and high rigidity. Can withstand axial, large radial, and tilting moment loads simultaneously.
Aplicaciones: robótica, Herramientas de máquina, Equipo medico, heavy machinery like large cranes and excavators where high accuracy and rigidity are paramount. Generally limited to lower continuous slewing speeds compared to ball bearings.
Double-Row Ball Slewing Bearings:
Characteristics: Three races with two rows of steel balls (often different diameters). Good for large axial forces and tilting moments.
Aplicaciones: Tower cranes, truck cranes, and other loading/unloading machinery requiring medium to large diameters.
Three-Row Roller Slewing Bearings:
Characteristics: Three separate raceways for upper, lower, and radial rollers. Can accurately determine the load on each row. Offer the largest bearing capacity among standard types, with firm structure and large shaft/radial dimensions.
Aplicaciones: Heavy machinery requiring large diameters, such as bucket wheel excavators, marine cranes, ladle slewing equipment, and large tonnage truck cranes.
3. Evaluate Rotational Speed and Performance
Speed Requirements: Determine the maximum operating speed. Four-point contact ball slewing bearings generally have higher speed capabilities and lower friction than crossed cylindrical roller bearings.
Friction and Efficiency: Lower friction leads to less heat generation and more efficient rotation.
Exactitud: For applications requiring precise positioning (p.ej., robótica), select bearings with minimal clearance and high manufacturing precision.
4. Account for Environmental Conditions
Rango de temperatura: Standard bearings typically operate between -30°C and 120°C. Extreme temperatures (very high or low) may require special materials, lubricants, and sealing.
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