Study and Calculation of Torsional and Bending Strength of Ball Screw Shaft Terminals

Today, we are going to discuss the "Study and Calculation of Torsional and Bending Strength of Ball Screw Shaft TerminalsHere is a note about "TheIn selecting ball screws, some people may be surprised that they do not calculate the strength of the shaft end.

Before,How to calculate allowable load in ball screw axial directionAs I wrote in the article "The strength of ball screws is not a problem when looking at the strength of the shaft diameter alone," but in most cases, the shaft terminal shape is a stepped small diameter due to the use of support units, etc. Therefore, when 3 times the rated torque is applied by a servomotor, etc., the ball screw may not have enough torsional strength. However, in most cases, this shaft end shape is stepped and small in diameter due to the use of support units, etc. Therefore, when 3 times the rated torque is applied by a servo motor, etc., the torsional strength is insufficient.Therefore, it is necessary to calculate whether the shaft end of the ball screw is strong enough in time to take the torsional and bending loads when transmitting torque.

Strength Calculation of Ball Screw Shaft Terminals

How to calculate the "torsional load" that a shaft terminal can take 

When a torsional load acts on the shaft end of a ball screw, check the torsional moment that may be applied to the shaft diameter. The planned selection ofBall screw shaft terminal diameter and material strength areIf the screw cannot handle the expected torque and torsional moment, change the shaft end diameter or increase the size of the ball screw.Please reconsider.

*Please see the Excel calculation sheet for the formula.

Calculation method for bending loads to which axial terminals are subjected  

For example, if the shaft end of a ball screw is not centered with the motor to which it is connected, it will be subjected to a bending load, and if the drive is relayed or turned back by a pulley, etc., the shaft end will be subjected to a bending moment.

*Please see the Excel calculation sheet for the formula.

Calculation method when the shaft terminal is subjected to "torsion" and "bending  

When torsion and bending are applied to the shaft end of a ball screw at the same time, calculate the equivalent bending moment and equivalent torsional moment, and use the more adverse value as the calculation result.

*Please see the Excel calculation sheet for the formula.

Download Calculation Sheet

Here you can download the calculation sheet. Please feel free to use it if it is available.*The allowable torsional stress and allowable bending stress in the calculation sheet are THK's values. When evaluating ball screws other than THK's ball screws, please change the material properties of the ball screw shaft.

Study and calculation of shaft end strength of ball screw_191130

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