Abstract: There are provided an electrode tip dressing apparatus and an electrode tip dressing tool for resistance welding, which are miniaturized by reducing a rotational driving-force of a dressing tool. By adjusting a curvature radius of a dressing portion 4 of a dressing tool 2, a contact width, wherein a top electrode tip 5 abuts to the dressing portion 4 of the dressing tool 2, is adjusted from a rotational center of the dressing tool 2 to the outer side of the dressing tool 2. Dressing work done with the dressing tool 2 is thus made to be constant at the whole area of the dressing portion 4, from the rotational center of the dressing tool 2 to the outer side of the dressing tool 2. Accordingly, excess dressing work, which brings decline of productivity, can be avoided, thus enabling to dress the top electrode tip 5 with the minimal dressing work. A rotational driving-power of the dressing tool 2 is thereby reduced, enabling to labor-save and miniaturize the electrode tip dressing apparatus.

Abstract: There are provided an electrode tip dressing apparatus and an electrode tip dressing tool for resistance welding, which are miniaturized by reducing a rotational driving-force of a dressing tool. By adjusting a curvature radius of a dressing portion 4 of a dressing tool 2, a contact width, wherein a top electrode tip 5 abuts to the dressing portion 4 of the dressing tool 2, is adjusted from a rotational center of the dressing tool 2 to the outer side of the dressing tool 2. Dressing work done with the dressing tool 2 is thus made to be constant at the whole area of the dressing portion 4, from the rotational center of the dressing tool 2 to the outer side of the dressing tool 2. Accordingly, excess dressing work, which brings decline of productivity, can be avoided, thus enabling to dress the top electrode tip 5 with the minimal dressing work. A rotational driving-power of the dressing tool 2 is thereby reduced, enabling to labor-save and miniaturize the electrode tip dressing apparatus.

Abstract: A resistor welding machine control method for calculating a temperature distribution at a portion to be welded by using changes in welding current and voltage across two welding electrodes during welding and information on sheet combination sequence at a spot-welding position, and for controlling at least the welding current or pressure applied to the electrodes by using the calculated temperature distribution. The present invention can thus provide a resistor welding machine control method capable of controlling welding quality accurately. Spot-welding position information, wear comparison information and the like are available as other information.

Abstract: A spot welding method and apparatus having electrode tips one of which is driven by a servo motor. In the method and apparatus, it is determined whether or not an abnormal condition occurs. The abnormal condition includes (a) squeezing some obstacle between the electrode tip and a workpiece, (b) a temperature adhesion of the electrode tips with the workpiece, (c) uneven pressurizing of the workpiece by the electrode tips, (d) a weld nugget dispersion, and (e) a too large electric resistance between the electrode tips and the workpiece. When such abnormal condition is detected, some counter measure is taken to prevent or decrease the abnormal condition.

Abstract: A method for controlling a welding current in a resistance welder which phase-controls an A.C. power supply voltage by a thyristor to control the welding current to a target value. Prior to supplying the welding current, a test current is supplied to measure a power-factor angle of a load. A plurality of curves representing relations between the welding currents and control voltages to a phase-shift pulse generator for a plurality of power-factor angles of the load are presets and one of the curves is selected in accordance with the selected power-factor angle of the load. A variation of the A.C. power supply voltage is measured. A period of a pulse generated by the phase-shift pulse generator is controlled based on a value determined in accordance with the selected curve and the measured variation of the A.C. power supply voltage to control a firing angle of the thyristor.

Abstract: A resistance spot welding method and apparatus wherein a weld can be judged to have an acceptable strength whether a splash (expulsion of weld metal) has occurred or not, provided that a maximum displacement (M) of a movable electrode to a fixed one is larger than a certain predetermined reference value (M.sub.L) or a rate (R) of the displacement at an initial stage is larger than a certain predetermined reference value (R.sub.L) which is defined between two certain predetermined reference values (R.sub.1, R.sub.E), by sensing the displacement and the rate thereof. Furthermore, when necessary, a weld is judged to have an acceptable indentation (I), as well, by sensing a position of the electrode at a specific point of time when a predetermined holding time has elasped from the time of de-energization of the welding current. Thus reliability of a spot welded joint is much improved and costly rejection of a welded product is considerably reduced.