Nowadays, ball screws are widely used in machine tools, aircraft and missiles, especially for wire-controlled electric flight; in automotive power steering, the rotary motion force is converted from the motor to the axial of the steering rack. In addition, ball screws are also used in robots and precision assembly equipment. Some high-precision ball screws are used in steppers in semiconductor manufacturing to achieve higher accuracy.
In mechanics, a ball screw device is a mechanical linear actuator that translates rotational motion to linear motion with some friction forces. A threaded shaft can offer a helical raceway for ball bearings which move as a precision screw. Like it is able to apply or withstand high thrust loads, they can do so with minimal frictions inside the device, making the operation much smoother.
The manufacturing tolerance of the above mechanism is very small, so it is suitable for manufacturing with high precision requirements. The ball assembly acts as the nut in the design while the threaded shaft here is the screw.
In contrast to the conventional lead screws, ball screws tend to be rather bulky, because of the fact that they need to have a mechanism to re-circulate the balls. At the same time, another form of linear actuator based on a rotating rod is a thread-less ball screw, known as the "rolling ring drive”.
In this design, three or even more rolling-ring bearings are arranged symmetrically in a housing surrounding a smooth (thread-less) actuator rod. And, the bearings are set at an angle to the rod, and this angle determines the direction and rate of linear motion per revolution of the rod.
Compared with the traditional ball screw and lead rod, the most advantage of this design is to eliminate the backlash and load caused by the pre-tightening nut, which brings many benefits to the machine mechanism and operation.
Similar to linear motors, linear motors are devices designed to convert specific energy sources into linear mechanical energy. One of the most commonly known examples is a heat engine, such as an internal combustion engine, which burns fuel (such as gas) to generate heat, which is then used to do work. At the same time, electric motors convert electrical energy into mechanical motion, pneumatic motors use compressed air, and spring motors in clockwork toys use elastic energy. In summary, the linear motor generates linear force from the power supply, thereby achieving stable motion.
The ball screws are H.M. Stevenson and D. Glenn. They were released in 1898, with patent numbers 601,451 and 610,044. With the development of the industrial revolution, the demand for mechanical stability has greatly increased, and the demand for ball screw performance has become more and more clear.
In the early days, manufacturing started with low-precision screw shafts. Later, the standard method was to grind the shaft with several spring-loaded nut laps. Then, repeatedly measure the pitch of the shaft and check against the distance standard.
Today, similar procedures are sometimes used to produce reference screw shafts, or to manufacture screw shafts. The ball screw is applied to the Deployable Tower Assembly structure on the James Webb Space Telescope.
Because the machine tool is the most basic equipment of the manufacturer, and has a critical impact on the final quality of the product, the quality of the machine tool itself is very important, and the performance of the machine tool is also innovative from time to time.
Now after the invention of the machining centers and the programmed controlling system (CNC, computer numerical control), the standards of machining become more and more rigid compared with the standards before. Besides the CNC machining centers, there are also CNC turning centers, CNC milling machines, CNC tapping and milling centers, CNC drilling and milling centers, and many other models.
The invention of the ball screw can be traced back to a very early time, and until recently, the ball screw was widely used in the industrial field. The rigidity of the ball screw provides stable mechanical motion for industrial users, so it has become one of the key components of the machine tool industry and other manufacturing industries, and is highly favored by the industry.
With the continuous development and research of metal materials, people expect that the quality of ball screws will be improved in the near future.
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