This section provides overview, applications, and principles of ball screws. Also, please take a look at the list of 33 ball screw manufacturers and their company rankings.
A ball screw is a form of feed screw that converts rotational motion into linear motion to move the position of a component.
The screw shaft and nut are actuated by a ball. As the screw shaft and nut rotate relative to each other, the balls roll in an endless cycle. The sliding resistance between the screw and nut is much lower than that of conventional trapezoidal screws.
The precision grade of the screw and ball allows for precise motion, resulting in high positioning accuracy. They are used in automotive steering devices and precision machine tools.
Ball screws are machine elements that convert the rotational motion of a motor, etc., into linear motion. Major applications include product and parts transportation, semiconductor manufacturing equipment, industrial robots, and machine tools. Since the amount of travel (lead) per revolution of a ball screw can be precisely reproduced, high positioning accuracy can be achieved by combining it with a stepping motor.
In NC-controlled machine tools, ball screws are used to configure the feed mechanism and obtain precision positioning accuracy. Ball screws are also used in food machinery, medical equipment, robots, injection molding machines, printing equipment, amusement equipment, automobiles, trains, aircrafts, semiconductor manufacturing equipment, and inspection equipment.
A ball screw is a machine element component consisting of a screw shaft, nut, and ball that converts rotational motion into linear motion or linear motion into rotational motion. It is a component using tribology technology in which a ball is placed between the screw shaft and nut to allow for light rolling motion. It converts sliding contact motion on the screw surface into rolling contact motion. Balls need to circulate infinitely, so circulating parts are required.
There are several types of recirculation systems, such as return tube type, end deflector type, end cap type, and piece type, as well as return plate type, and their applications are classified according to size and precision. In order to use a ball screw, a guide rail is required to guide the nut. Guide rails bear vertical loads and moment loads other than the axial load applied to the nut.
The threaded shaft is made to move with high accuracy by combining the length of the lead, which is the amount of movement per nut revolution, with the number of threaded strips. The ball is pressurized to eliminate nut backlash and obtain high positioning accuracy without uneven rotation of the screw shaft and nut.
Ball screws are characterized by their ability to convert the rotational motion of a machine into linear motion. Conversely, it can also convert linear motion into rotational motion. The torque to drive the screw shaft rotation can be reduced to 1/3 or less compared to that of an ordinary screw. Therefore, the motor that drives the ball screw can be made smaller and lighter.
The difference between starting frictional torque and kinetic frictional torque is small, and stick-slip phenomenon can be avoided, enabling high-precision machine control. Nuts can be preloaded by using two nuts or by using balls with a larger diameter in advance. Backlash is eliminated and rigidity is increased, resulting in better controllability.
The wear life and rolling fatigue life of the ballscrew can be predicted by calculation, thus increasing operational reliability. The coefficient of friction at the contact surface between the screw and nut is about 0.1 to 0.2 for sliding screws, whereas it is 0.002 to 0.004 for ball screws. Therefore, the transmission efficiency is high at over 90%.
Since dimensions and accuracy are internationally standardized and mass-produced in dedicated factories, they are easy to use and cost-effective. On the other hand, ball screws have the disadvantage of being vulnerable to impact. Since the sliding parts are in point contact, they are prone to leave dents and other marks when subjected to impact. In addition, foreign matter entering the sliding parts may cause malfunctions or failures. When used as a slide shaft of a machine tool, it is necessary to cover it with a cover, etc., to prevent chips from getting into it.
Ball screws are classified into "rolling" and "grinding" depending on the manufacturing method.
Rolling Ball Screw: In this method, a round bar is pressed against a tool called a rolling die while rotating to form a threaded groove by plastic deformation. Compared to grinding, the accuracy grade tends to be lower.
Ground Ball Screw: This method uses a machine tool called a thread grinder to form the thread groove by grinding. Since cylindrical grinding is performed after heat treatment, the surface is smoother than that of rolling. This method is used when high-precision machine control is required, such as for slide axes of small machine tools for precision instruments.
*Including some distributors, etc.
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