Hojama rolled ball screw
How to Eliminate Backlash in Ball Screw Assembly
1. Readjust or regrind to achieve a contact rate of over 70%. It is considered qualified if a 0.03mm feeler gauge cannot be inserted.
2. Utilize the automatic compensation function of the control system to eliminate gaps. Measure and adjust the axial movement of the linear screw using instruments.
3. Adjust the preload and check the axial runout value to ensure the error does not exceed 0.015mm.
4. Perform repair and adjustment.
5. Adjust until each guide rail surface is properly lubricated.
6. Retighten and conduct repeated tests with a dial indicator.
7. Remove the interfering parts.
8. Carry out repair, adjustment, or gasket addition as needed.
DN Value of Ball Screw
1. Definition of DN Value
The high-speed performance of ball screws is evaluated by the DmN value. Here, Dm represents the pitch circle diameter (P.C.D) of the upper and lower balls in the ball screw, and N is the maximum rotational speed of the screw. Therefore, the DmN value indicates the revolution speed of the balls, and it also serves as the designed high-speed limit of the ball screw. For the convenience of calculation, the outer diameter D of the ball screw is used instead of Dm. For example, for a 50ψx 30 ball screw, when the maximum rotational speed of the screw is 3000 rpm, the DN value can reach 150,000, and the maximum feed rate is 90 m/min.
2. Differences between High DN Value and High Lead
High Lead: By increasing the lead of the linear ballscrew, the feed rate is enhanced. For instance, in applications that require rapid movement of the load, a high-lead ball screw can achieve a faster linear speed at the same rotational speed of the motor.
High DN Value: It involves an effective balance between the rotational speed and the lead, taking into account issues such as accuracy, dynamic and static loads, critical speed, vibration induced by inertial forces, and temperature rise caused by high-speed operation. In high-speed machining centers, a high-DN-value ball screw is selected to ensure both high-speed movement and high-precision positioning. High-speed operation may lead to problems like increased friction, which can cause temperature rise and affect the accuracy of the ball screw. A high-DN-value ball screw is designed to mitigate these issues through optimized design and material selection.
