Introduction of Ball Screw

Ball Screw is a feed screw that turns the radial motion into linear motion by making a rolling motion between the screw’s ball channel and the nut’s ball recirculaiton channel.The reason for using it instead of trapezoidal shaft is high efficiency. Due to the ball between the nut and the shaft, the friction effect is less compared to the trapezoidal shaft.

Types Of Ball Screw Shaft

Screw shafts are divided into two according to the way they are manufactured.

  • Rolled Ball Screw Shaft

Areas where such shafts are used are generally applications where the load must be transported from one place to another. Positioning accuracy is not critical in this type of application.The easiest way to find out that the ball screw is a rolled type is to see that there is a narrow channel line on the shaft, except for the ball raceway.They are known on the market as C7, C8 or C10 quality (or the letter T is used instead of C).rolled ball screw shaft

  • Ground Ball Screw Shaft

Ground ball screws are used especially in applications requiring precision and high repeatability.Quality coding is available as C5, C3, C1 or C0. Since the grouding process increases the resistance of the ball raceways, they can be used in applications with higher load.They work quieter than rolled shafts.

ground ball screw shaft

Ball Screw Nut

In the picture, as you can see the internal structure, there are grooves in the ball screw nut where the balls will roll.There are also circulation channels on the body of the nut so that the balls can rotate without jamming.

The most important value for ball screw nuts is the preload class.As the preload class of the nut increases, the positioning accuracy of the system increases (G0 high, G3 low).The preload class is provided by adjusting the ball diameters inside the nut.internal view on ball screw nut

OverLoad exposure or incorrect product selection

If the proper product is not selected, nut balls may spill or the shaft may break.

broken ball screw nut flange side broken ball screw nut body side

Machined ball screw end example

In the picture, the machining example of the screw shaft fixed end is shown.This process should be done with high precision.In the case of axial misalignment, the ball screw may jam, break or make noise at high speed .

machined ball screw fixed side

Machined ball screw 3D data sample view

Some programs may export the data as preprocessed (ex THK Online Tool at partcommunity).

machined ball screw 3d view

Assembled view of fixed and support end bearings of the ball screw

BK12 (fixed side) and BF12 (support side) end bearings were used in this assembly work together with the EBB1605 type ball screw.

assembly of fixed and supported side of ball screw

We will touch on detailed screw shaft selection in our next posts.

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