Abstract: The driving apparatus for the rotation of the spindle or the work piece pallet of an electroerosive machining device comprises two electric motors which drive e.g. the spindle to a rotational movement by means of two gear boxes and a plurality of gear wheels. In order to avoid any backlash in the gear box and any clearance between the gear wheels and to compensate the elasticity of the gear transmission, the two electric motors are always operated to rotate in opposite directions and/or to yield different values of torque. Thus, the entire transmission assembly is always subjected to a certain bias force so that a precise positioning of the spindle is possible by means of simple and inexpensive driving elements.

Abstract: In electro-erosive machining apparatuses with multidimensional relative motion between a tool-electrode and a workpiece electrode, a simple and adaptable control is provided for these relative operating movements, with a superimposed shaping-limiting control and subordinated cyclic repetitive oblique erosion. In this connection, the tool-feed is limited, within individual oblique-erosion cycles, by achieving a predetermined shaping envelope-surface. The apparatus comprises two separate coordinating-function-transmitters by means of which two operating movements, at an angle to each other, are each determinable according to a resultant relative operating movement between the tool and the workpiece, one being used for shaping-limiting control and the other for oblique erosion. Initiation of the consecutive oblique-erosion cycles is effected by means of a repetition-circuit as a function of a rated-value/actual-value approximation of the shaping-limiting control.