Rigidity

This is the rigidity in the ball contact zone in the case of two opposing and preloaded nuts with preload Pc = 0.10•Ca and applied external force Fa=3•Pc. Rigidity Rc  for a single nut under the same load F_a  is equal to 0.5•0.5•R_S.

In designing any precision machine with recirculating ball screws it is necessary to bear in mind the global rigidity of the kinematic complex (of which the screw is a part) made up of:

- screw

- nut

- support bearings.

Screw rigidity is given by the following formula:

d_m

 average diameter (on point of ball contact)(mm)

E

 modulus of elasticity of steel 21,000 (daN/mm 2 )

l₁

 unsupported length (mm)

Rigidity of the single nut is given by the following formula:

R_s

rigidity of balls as indicated in double nut dimensional

tables

The rigidity of the support bearings:

depends on the type of bearings and on the type of

support (values given in bearing catalogues)

Global rigidity of the system is given by the formula: