What Are The Main Points of Ball Screw Selection Design?

When selecting the ball screw,we must first clarify its operating conditions.The factors that affect ball screw selection include load,stroke,torque,positioning accuracy,repeated positioning accuracy,rigidity,lead and nut aperture.These elements are interrelated.The change of any one factor will have an impact on the other factors,so it is necessary to pay attention to the balance between the factors.

ALM large rolled ball screw

ALM micro rolled ball screw

ALM large ground ball screw

ALM mini ground ball screw

●Accuracy:C10<C7<C5<C3

The smaller value of the ball screw,the higher the accuracy,but the higher the cost.Rolled C7 ball screw is the most commonly used accuracy grade and is also the default accuracy when selecting.Ground C5 ball screw is a commonly used high precision grade.

●Shaft diameter: the outer diameter of the ball screw thread
It is closely related to the design load of the ball screw.The ball screw load includes dynamic load and static load,and the design mainly refers to dynamic load.From the perspective of life it should be ensured that the physical load under the working condition is < the dynamic load of the ball screw,that is,to reduce the full load and leave as much margin as possible.

●Lead:the ball screw rotates once,the distance the nut moves

It is related to the speed of the design,and the ball screw speed is an important factor affecting the lead.Recommended speed of ball screw <1500r/min.If noise is not considered,the speed should be ≤2000r/min(the maximum speed should not be greater than 2500r/min).

In addition,leads involve two parameters: pitch P and the number of lines n.

(1)Pitch (P): The axial distance between two adjacent teeth on the bus bar of the middle diameter cylinder.

(2)Starts(n):The number of thread starts.For ease of manufacture,there is usually a limit of n≤4. The lead can be calculated by the formula,lead = pitch*starts, expressed as S=p*n

●Length:effective tooth length and total length of ball screw

In the design process,it is first necessary to determine the design stroke,and then according to the stroke to determine the effective tooth length of the lead screw,and finally calculate the total length.There is a proportional relationship between the maximum length of the ball screw and the shaft diameter,that is,the slender ratio is 60,which means that the maximum length of the ball screw is less than the shaft diameter *60.

For more information about ball screw,please contact us email:sales@autolinearmotion.com

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