Electromechanical as well as hydraulic drives are used. Figure 7.5 shows a schematic
diagram of an electromechanical table drive of a double-column planning machine. The
conversion of the rotary movement of the electric motor and the associated gear box into the
translatory movement (TRS) of the table is achieved by the use of two rack and pinion drives.
The two racks are displaced by half of one tooth space. As a result an improved overall tooth
contact is maintained, and a more even power transmission is obtained. The axial forces
resulting from the helical tooth form are cancelled out because of the opposing helix angles of
the teeth.
The input shaft of the main drive is fitted with axially floating bearings. As a result of this and
the helical teeth, the turning moment is evenly distributed between the two drives. This
machine needs a large floor space since the machine bed is twice as the machine table.