What is a Ball Screw Bearing?
Ball screw bearings are an essential component of many industrial and mechanical systems. They are used to transfer rotational motion into linear motion with high precision and efficiency. In this blog, ATO will discuss what a ball screw bearing is and its features.
What is a ball screw bearing?
A ball screw bearing is composed of a screw, a nut, a reverse device, and a ball for converting rotary motion into linear motion or converting linear motion into rotary motion. The ball screw bearing is a type of rolling-element bearing that uses balls to reduce friction and transfer motion between two parts. The bearing comprises a threaded shaft and a nut with matching ball grooves. The balls roll between the grooves, allowing the nut to move linearly along the shaft.
Ball screw bearings come in various designs, including single-start and multi-start threads, which affect their lead and torque capacities. They can be configured with different ball recirculation systems, such as end-cap, tube, and deflector types, which affect their load capacity, rigidity, and noise level.
The ball screw pair is an ideal product for converting rotary motion into linear motion or converting linear motion into rotary motion. The ball screw pair is composed of a screw, a nut, a reverse device, and balls. The function of the ball screw pair is to convert rotational motion into linear motion or convert torque into axial repeated force, and at the same time, it has high precision and reversibility, and high-efficiency features.
The ball screw pair has the characteristics of high precision, reversibility, and high efficiency. This is the further extension and development of the trapezoidal screw. The significance of this development is to change the sliding action of the trapezoidal screw into a rolling action. Due to their small frictional resistance, ball screw bearings are widely used in various industrial equipment and precision instruments.
Ball screw bearings are commonly used on machine tools and the appropriate type can be selected according to the application. Ball screw pairs offer a wide range of standardized products to suit a variety of applications. The circulation methods of the ball include circulating catheter type, circulator type, and end cap type. Precompression methods include positioning pressure (double nut method, position precompression method), and constant pressure preloading. Screws are available in precision ball screws with high-precision grinding (accuracy is divided into 7 grades from CO-C10) and cold-rolled ball screw bearings that are formed by high-precision cold rolling (accuracy is divided into 3 grades from C-C10, and only a few can achieve this). In addition, to meet the urgent needs of users, there are finished products that have been processed on the shaft end, semi-finished products that can be freely top-processed at the shaft end, and cold-rolled ball screw bearings. As the peripheral parts of this bearing, the necessary screw support unit, nut support, lock nut, etc. have also been standardized and can be used by users.
As you can see, the above picture is the 8mm ball screw bearing sold by ATO, with C7 precision grade, small friction loss, high transmission efficiency, compact design, and easy to install and disassemble.
Characteristics of ball screw bearings
So what are the characteristics of ball screw bearings when used? Ball screw support bearing product features are as follows:
1. High transmission efficiency
The transmission efficiency of the ball screw drive system is as high as 90%~98%, which is 2~4 times that of the traditional sliding screw system, so it can get a larger thrust with less torque, and can also be converted from linear motion to rotary motion (reversible motion).
2. Smooth motion
The ball screw drive system is a point-contact rolling motion, with low friction resistance during operation, high sensitivity, no chatter at start-up, and no crawling phenomenon at low speed, so the micro feed can be precisely controlled.
3. High precision
The temperature rise of the ball screw transmission system is small during motion, and it can be pre-tightened to eliminate the axial gap and pre-stretch the screw to compensate for thermal elongation, so high positioning accuracy and repeat positioning accuracy can be obtained.
4. High durability
The rolling contact parts of the steel balls are all hardened (HRC58~63) and precision ground. The circulation system process is purely rolling, with relatively little wear, so it has a high service life and precision retention.
5. Good synchronization
Due to the smooth, responsive, non-blocking, and non-slip movement, good synchronization can be obtained by using several sets of the same ball screw drive system to drive several identical parts or devices at the same time.
6. High reliability
Compared with other transmission machinery and hydraulic transmission, the ball screw transmission system has a very low failure rate, and the maintenance is simpler, only general lubrication and dust prevention are required. In special cases, it can be operated without lubrication.
7. No backlash and high rigidity
The ball screw transmission system adopts the Gothic arch groove shape so that the steel ball and the groove can reach the best contact for easy operation. If proper preload is added to eliminate the axial clearance, the balls will have better rigidity, reducing the elastic deformation between the balls and the nut and screw to achieve higher precision.
8. Not self-locking, reversible with transmission
Anti-reverse rolling screw transmission has a high reverse rate and cannot be self-locking. To prevent the screw pair from reversing after being stressed, an anti-reversing device should be considered, such as using a brake motor, a stepping motor, and a self-locking mechanism (such as a worm drive) in the transmission system. Install one-way clutches, two-way clutches, brakes, etc. in nuts, leadscrews, or transmission systems. When selecting a clutch, attention must be paid to its reliability. Prevent nuts from falling out In rolling screw transmission, especially vertical transmission, it is easy to cause accidents caused by nuts falling out, so safety devices to prevent nuts from falling out must be considered in the design.
ATO provides 6 ball screw support bearing models: BK, EK, AK, BF, EF, and AF, with low prices and high precision. The shaft diameters of ball screw bearings are available in 4mm, 6mm, 10mm, 25mm, and 40mm, and the precision grades are C5 and C7. Welcome to the ATO online store for consultation and purchase.
