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Motor Bearing
Published in Wei Tong, Mechanical Design and Manufacturing of Electric Motors, 2022
A ball screw is a special motion-transfer actuator that combines a ball bearing and a screw together to convert rotational motion into linear motion with negligible rolling friction. During the motion-transfer process, loads are transferred from the screw shaft to the nut through a set of rolling balls. As shown in Figure 6.19, the ball screw assembly primarily consists of four components: a screw shaft, a ball nut, a ball recirculation system, and a plurality of bearing balls [6.14]. The screw and nut have matching helical grooves and balls roll between these grooves. To cope with the high axial forces as the screw shaft rotates in either direction, angular contact bearings or thrust bearings may be adopted at two ends of the screw shaft (not shown in the figure). Since the specially designed ball screw systems can take heavy loads and achieve high precision positioning, they are widely used in computer numerical control (CNC) machine tools and precision positioning tables.
Power Screws, Fasteners, and Connections
Published in Ansel C. Ugural, Mechanical Engineering Design, 2022
Efficiencies of 90% or greater are possible with ball screws over a wide range of helix angles when converting rotary into axial motion. Ball screws may be preferred by the designers if higher screw efficiencies are required. As a positioning device, these screws are used in many applications. Examples include the steering mechanism of automobiles, hospital bed mechanisms, automatic door closers, antenna drives, aircraft controls (e.g., a ball or jack screw and gimbal nut assembly as an actuator on a linkage for extending and retracting the wing flaps) and landing-gear actuator, jet aircraft engine thrust reverser actuators, and machine tool controls. Because of the low friction of ball screws, they are not self-locked. An auxiliary brake is required to hold a load driven by a ball screw for some applications.
Power Screws, Fasteners, and Connections
Published in Ansel C. Ugural, Youngjin Chung, Errol A. Ugural, Mechanical Engineering Design, 2020
Ansel C. Ugural, Youngjin Chung, Errol A. Ugural
A ball screw, or so-called ball-bearing screw, is a linear actuator that transmits force or motion with minimum friction. A cutaway illustration of a ball screw, and two of its precision assemblies supported by ball bearings at the ends are shown in Figure 15.9. Note that a circular groove is cut to proper conformity with the balls. The groove has a thread helix angle matching the thread angle of the groove within the nut. The balls are contained within the nut to produce an approximate rolling contact with the screw threads. The rotation of the screw (or nut) is converted into a linear motion and force with very little friction torque. During the motion, the balls are diverted from one end and the middle of the nut and carried by two ball-return tubes (or ball guides) located outside of the nut to the middle and opposite end of the nut. Such recirculation allows the nut to travel the full length of the screw.
Construction of dynamic temperature field model of ball screw based on superposition of positive and negative temperature fields
Published in Numerical Heat Transfer, Part A: Applications, 2023
Huayang Wu, Qiang Guan, Chenfei Xi, Dunwen Zuo
Machining center, characterized by high speed and efficiency, is often used in aerospace, automobile, and other fields, and can achieve precision and ultra-precision machining. Ball screw plays a key role in numerical control (CNC) machine tools, which can convert rotary motion into high-precision linear motion [1]. The ball screw error includes thermal error, geometric error and error caused by force, among which the error caused by thermal deformation accounts for 40% ∼ 70% of the total error [2]. Each heat source of the ball screw feed system produces a lot of heat during operation, resulting in large thermal error and thus directly affecting the machining accuracy of the machine tool. Therefore, in order to take more effective measures to reduce thermal error, it is of great significance to study the relationship between temperature distribution, heat source and thermal deformation of ball screw feed system.
Theoretical and Experimental Study on a Cam-Type Response Amplification Friction Damper
Published in Journal of Earthquake Engineering, 2023
Guifeng Zhao, Jiajia Chen, Yuhong Ma, Peng Xie, Zhenyu Yang
The ball screw, which is widely used in mechanical engineering (Tiancheng et al. 2017; Yousuf 2019), shows high reliability and allows large axial strokes. Particularly, the ball screw with rotational mass, like a tuned viscous mass damper, is already adopted in structures (Ikago et al. 2012; Kida et al. 2011; Saito, Kurita, and Inoue 2007). Therefore, inspired by the ball screw and tuned viscous mass damper, this study proposed an innovative friction damper for passive control of buildings.