How accurate are ball screws?

How accurate are ball screws?

Knowing the key characteristics necessary to manufacture a precision ball screw helps in selecting the right one and ensuring a long product life. Few, if any, external factors provide clues about the quality of a precision ball screw, defined as those ball screws having an accuracy to within 5 microns.

What is C7 accuracy?

The accuracy of the Ball Screw in lead is controlled in accordance with JIS standards (JIS B 1192 – 1997). Accuracy grades C0 to C5 are defined in linearity and directional property, and C7 to C10 in travel distance error in relation to 300 mm.

What is a typical ball screw efficiency?

Ball screws offer a high level of mechanical efficiency. Statistics show that ball screws are about 90% efficient, meaning they are able to convert nine-tenths of the application’s rotational motion into linear motion. In comparison, lead screws have an average mechanical efficiency of just 20% to 25%.

How can you tell if a ball screw is bad?

If your ball screw shows signs of pitting or corrosion from contaminants, it is deteriorating. If it shows signs of heat discoloration and operates roughly (wobbles, chatters, growls, etc.), it is likely inadequately lubricated, misaligned and/or has worn/damaged bearings.

How do you reduce backlash in ball screws?

To eliminate ball screw backlash while maintaining a low and smooth torque, thread whirling or precision thread grinding is required. Once the ball screw backlash has been eliminated from the nut, it is still necessary to constrain the lead screw axially.

Do ball screws have backlash?

Backlash is caused by the clearance between the ball bearing elements and the screw and nut tracks resulting in lost motion in the screw. A ball nut with all the backlash removed is called preloaded.

What is the purpose of ball screw?

Ball screws are used in aircraft and missiles to move control surfaces, especially for electric fly by wire, and in automobile power steering to translate rotary motion from an electric motor to axial motion of the steering rack. They are also used in machine tools, robots and precision assembly equipment.

How do you calculate ball screw load?

Thus, the maximum axial load applied on the Ball Screw is as follows: Fa max = Fa 1 = 550 N Therefore, if there is no problem with a shaft diameter of 20 mm and a lead of 20 mm (smallest thread minor diameter of 17.5 mm), then the screw shaft diameter of 30 mm should meet the re- quirements.

How do you check a ball screw backlash?

Measuring for Ball Screw Backlash and Table Movement

1. Place a magnetic base indicator directly on the screw.
2. Place the magnetic base indicator on the ball screw and put the pointer on the bearing support block.
3. Place the magnetic base indicator on the screw and the pointer on the ball nut housing.