The diameter of the screw shaft is one of the main dimensions of a ball screw, typically measured in millimeters (mm). A larger screw shaft diameter results in higher load-carrying capacity, rigidity, and precision. Load-carrying capacity refers to the maximum axial force that the ball screw kit can transmit, while rigidity determines the ball screw's ability to resist deformation under force.?
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When selecting the ball screw diameter, it is necessary to consider the load, speed, and precision requirements of the application scenario. In general, scenarios with high load, high precision, and high rigidity requirements call for ball screws with larger diameters.
2. Lead
The lead is the distance that the driven part moves along the axis per full rotation of the screw shaft, also measured in millimeters (mm). A larger lead means a greater axial movement per rotation, indicating a higher motion speed of the screw. However, it should be noted that an increase in lead is usually accompanied by a decrease in precision, as balls are more susceptible to external forces over a longer lead.
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The selection of lead should be based on the speed and precision requirements of the ball screw system. High-speed systems typically require a larger lead to enhance motion speed, while high-precision systems need a smaller lead to reduce errors.
3. Ball Diameter
The ball diameter refers to the diameter of the balls in the ball screw assembly. Larger ball diameters result in higher load-carrying capacity, fatigue resistance, and rigidity. The minimum ball diameter of a linear ball screw is usually determined by the lead and nominal diameter, generally ranging from 3 to 4 mm.
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The choice of ball diameter depends on the load capacity and expected service life of the ball screw set. In scenarios with high load and high rigidity requirements, larger-diameter balls are typically selected. Additionally, the number and distribution of balls also affect the balll screw's performance, which needs to be comprehensively considered in the design.
4. Accuracy Class
The accuracy class of Hojama ball screw and nut refers to its tolerance range, which is usually divided into several grades such as C3 and C5. A higher accuracy class indicates higher precision of the ball screw pair and smaller motion errors. The selection of the accuracy class should be based on the requirements for positioning accuracy and repeat positioning accuracy in the application scenario.
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In high-precision scenarios, such as precision machine tools and semiconductor manufacturing equipment, high-accuracy class ball screws are required. In scenarios with lower precision requirements, such as ordinary mechanical transmission systems, lower-accuracy class ball screws can be chosen to reduce costs.
5. Axial Clearance
Axial clearance refers to the clearance of the ball screw and bal nut in the axial direction, i.e., the distance difference between the thread axis and the screw axis. The size of the axial clearance directly affects the positioning accuracy and rigidity of the screw. In the design and use of ball screw kits, efforts should be made to minimize axial clearance to improve performance.
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To reduce axial clearance, preloading measures can be taken, such as using preloaded nuts or adjusting the preload force. Preloading can eliminate axial clearance and enhance the rigidity and positioning accuracy of the ball screw. However, it should be noted that excessive preload may increase friction and wear, so a balance needs to be struck in the design.
6. Rated Load
The rated load of a ball screw kit refers to the maximum load it can bear, including the rated dynamic load and rated static load. The rated dynamic load is the maximum dynamic axial force that the ball screw can withstand for a long time under specified conditions; the rated static load is the maximum static axial force that the linear motion screw can bear without plastic deformation under specified conditions.
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The selection of the rated load should be based on the type and magnitude of the load in the application scenario. In scenarios with high load requirements, ball screw assemblies with larger rated loads are needed. Furthermore, the fluctuation of the load should also be considered to select a ball screw capable of withstanding the maximum peak load.
7. Maximum Rotational Speed
The maximum rotational speed of a linear motion ball screw refers to the highest speed it can withstand, usually expressed in revolutions per minute (rpm). The selection of the maximum rotational speed should be based on the speed requirements of the application scenario.
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In high-speed motion scenarios, such as high-speed CNC machine tools and high-speed automated production lines, Industrial Ball Screws with higher maximum rotational speeds are required. However, it should be noted that as the rotational speed increases, the friction and wear between the balls and the screw shaft also increase, so comprehensive consideration is needed in the design.
8. Thread Form
The thread forms of ball screw sets are usually three types: triangular threads, circular threads, and rectangular threads. Different thread forms are suitable for different application occasions.
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Triangular threads are the most common, with high strength and rigidity, suitable for most transmission systems. Circular threads have smaller friction and wear, suitable for scenarios requiring high efficiency and low noise. Rectangular threads have high precision and rigidity, suitable for precision transmission systems.
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When selecting the thread form, it is necessary to consider the load, speed, precision, and noise requirements of the application scenario.
9. Other Parameters
In addition to the above main parameters, ball screw kits have other parameters such as nut diameter, flange diameter, nut length, and nut mounting PCD. These parameters are usually determined based on the ball screw's diameter, lead, and mounting form.
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The nut diameter and flange diameter determine the mounting size and connection method of the ball screw. The nut length affects the load-carrying capacity and rigidity of the ball screw. The nut mounting PCD refers to the circle diameter of the nut mounting holes, which determines the mounting accuracy and stability of the ball screw.
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Hojama is a professional ball screw manufacturer in China, we can offer all kinds of ball screw products, including mini ball screws, Precision Ball Screws, two-lead ball screws and Rolled Ball Screws. Welcome to make an order.
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