How to preload ball screws?

Preload is the installation of the rolling elements(balls)of a ball screw to produce axial loads.The type and amount of preload affects the stiffness of the ball screw and ultimately the life of the ball screw assembly.There are several ways to preload a ball screw.

●Ball screw with P-type preloading use oversized balls and a single ballnut

Type P preloading is the most cost effective option,using oversized balls and a single ballnut to improve performance.For example,a ball screw using P-type preloads the ball screw assembly up to 3% of dynamic capacity.P-type is suitable for shorter ballnut lengths;note that it also has lower torque characteristics than other preload options.

Ball screws with P-type.

●Z-type preload uses single-ballnut design with offset to center lead

Ball screw applications requiring higher rigidity typically benefit from either Z-type preload or D-type preload. Both of these preload types can be used with up to 10% dynamic capacity. type Z preload uses a single ballnut design that is offset from the center lead in the ballnut.In short,Type Z uses a ballnut to move the lead,thereby creating preload between the ball circuits.It is a less expensive option than Type D and provides excellent rigidity for medium ballnut lengths.

Shown here is an illustration of Z-type ball screw preload,a single-ballnut design with an offset from the center lead in the ballnut.

●D-type ball screw preload uses a double-ballnut design and precision spacer

Type D preload is the most expensive option because of its double ballnut design.It uses precision spacer to obtain the required preload.In this case,the manufacturer uses a key to hold the ballnuts together to obtain rigidity.More circuits can be added to the double ballnut and spacer design for higher load carrying capacity than the Z type.

The double ballnut and spacer design accepts more circuits than the Z option (which can increase load carrying capacity).

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