Figure 7
ball screw drive with play-free double nut
ball screw nut
Clamping ring
balls
Drive spindle
The manufacturing tolerances resulting from the manufacturing process of the ball screw drive can be rectified
by modern CNC controls using the spindle pitch error adjustment. For this purpose the tolerances are
measured by laser measuring systems and stored in the CNC control.
Path measuring systems
Depending on the applied measuring device or scale direct and indirect position measuring are differentiated
as well as absolute and incremental position measuring. The most accurate measuring values are achieved
with direct measuring scales.
In direct position measuring (see figure 8) the measuring scale is given in the carrier or on the machine
table so that inaccuracies on spindle and drive connection have no influence on the value measured.
The measuring values are specified by an optical pick-up on a scanning pattern of the measuring scale. The
pick-up converts these values into electrical signals and transfers them to the control.