Patent ID: 6906276

Claim:
A control device for spot welding with an electrode holder (Z), the welding electrodes (E 1 , E 2 ) of which are connected to a controllable welding current generator (IS), and which can be actuated to open and close by means of an electric motor drive (M) having a position sensor disposed on it, the signals of which are used by a control device (MP) to actuate the electrode holder (Z) to open and close according to predefined settings (psoll), and wherein, in the closed position of the electrode holder (Z), the same holds welding objects (B 1 , B 2 ) clamped between the welding electrodes (E 1 , E 2 ) by means of a predefined motor current (MAI), wherein the welding current generator (IS) is activated at certain times by the control device (MP), and wherein the position sensor is an angular-motion signal transducer, resolver (RES), and the control device (MP) comprises monitoring devices (const, max) to which the angular-motion transducer signals are continually routed and wherein, as soon as this monitoring device (const) senses a quasi standstill on the angular-motion transducer signals after a closing actuation of the electrode holder (Z), a corresponding first state is recorded as the closed position of the electrode holder (Z) and the welding current generator (IS) is activated and a time curve of a welding electrode distance (CTS) is then determined from the resolver signals (RES), in dependence upon which time curve the motor current (MAI) and/or the welding current of the welding current generator are pre-set with a different setting, so that the curve of the welding electrode distance (CTS) approximates a pre-recorded curve of an optimal welding process, characterized in that, in the closed position, the motor current (MAI) is regulated such that a welding electrode distance (CTS), which is continually determined by summing the angular-motion transducer signals (RES), is held nearly constant or according to a pre-set time curve.