Ball Screw Preloads and Metrics

Preloading is utilized to extend the nourish precision and unbending nature of ball screws. Why is this vital? In numerous applications utilizing ball screw activation, position exactness is of most extreme significance. With numerous ball screw driven actuators, position precision can be accomplished inside some microns. Any deviation seem compromise the plan expectation. Hence preloading is connected to decrease hub clearance between a ball nut and the screw shaft and to also accomplish exact situating. It is additionally vital to apply the correct sum of preloading to anticipate intemperate warm era through the ball screw’s anticipated life. On the “Axial Clearance” column of the ball screw selection chart:

① 0 (Preload)

② 005 or Less

③ 030 or Less

④ 10 or Less

Terminology	Details
Positional Preload	Preloading method considers the positional clearance of the screw shaft and steel balls.
Oversized Balls Method [Fig. 1]	This preloading method ensures 4 points of contact between the ball screw grooves and nut. This is accomplished by inserting slightly oversized steel balls.
Lead Shifted Method	This preload is applied by machining the nut with a groove offset at the center in the amount of desired preload.
Spacer Method [Fig. 2]	A preloading method using a spacer between a set of nuts to achieve the desired amount preload. Ideal for heavy preload.
Pin Method (For Heavy Preload)	Similar to the spacer method, the nut ends are machined to achieve the desired offset, then pinned together to prevent rotation among each other.
Predetermined Pressure Preload [Fig. 3]	The preload is applied with a spring.

If backlash or slip is not a major concern in your application, it is advised to choose a ball screw with larger clearance (directly related to accuracy grade). This will keep cost down and prevent overdesigning.

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