Seam welding is performed by clamping a coupling portion of an upper sash with a first roller electrode and a second roller electrode, and applying electricity while rotating first roller electrode and the second roller electrode. The first roller electrode includes a plurality of first projecting portions and second projecting portions that are at intervals in a circumferential direction around a first rotational center. The second roller electrode may include a plurality of first opposing projecting portions and second opposing projecting portions that are at intervals in a circumferential direction around a second rotational center, by clamping a coupling portion of an upper sash and applying electricity while rotating.

Seam welding is performed by clamping a coupling portion of an upper sash with a first roller electrode and a second roller electrode, and applying electricity while rotating first roller electrode and the second roller electrode. The first roller electrode includes a plurality of first projecting portions and second projecting portions that are at intervals in a circumferential direction around a first rotational center. The second roller electrode may include a plurality of first opposing projecting portions and second opposing projecting portions that are at intervals in a circumferential direction around a second rotational center, by clamping a coupling portion of an upper sash and applying electricity while rotating.

A sliding electric contact device for welding head for roller welding machines, having a bimetallic plate adapted to be fixed to a shaft of a welding head, having a protection base composed of a first metal, defining a first face destined to abut against an end surface of the shaft, and a sliding disk composed of a second metal softer than the first metal, defining a second sliding electric contact face; a composite current-carrying block, having a plait of electrical wires, an internal support made of metal, pushed against the sliding disk for realizing with the sliding disk a sliding electric contact, first means adapted to fix firmly a central portion of the plait to the inner support, second current-carrying means adapted to fix firmly a peripheral portion of the plait to current terminals of a stator of the welding head. A welding head having the sliding electric contact device and a related roller welding machine are also disclosed.

A sliding electric contact device for welding head for roller welding machines, having a bimetallic plate adapted to be fixed to a shaft of a welding head, having a protection base composed of a first metal, defining a first face destined to abut against an end surface of the shaft, and a sliding disk composed of a second metal softer than the first metal, defining a second sliding electric contact face; a composite current-carrying block, having a plait of electrical wires, an internal support made of metal, pushed against the sliding disk for realizing with the sliding disk a sliding electric contact, first means adapted to fix firmly a central portion of the plait to the inner support, second current-carrying means adapted to fix firmly a peripheral portion of the plait to current terminals of a stator of the welding head. A welding head having the sliding electric contact device and a related roller welding machine are also disclosed.

A laminate formed by stacking a plurality of workpieces is sandwiched between a pair of roller electrodes. Then, seam welding is performed on the laminate by successively repeating an ON/OFF operation of a conduction state between the pair of roller electrodes while moving the laminate relative to the pair of roller electrodes. When the seam welding stops in a state where the pair of roller electrodes are unpowered and then the seam welding is to be resumed, the laminate is moved by a predetermined distance in a direction opposite to the relative moving direction during seam welding, spot welding is performed on the laminate, and then the seam welding is resumed.

A laminate formed by stacking a plurality of workpieces is sandwiched between a pair of roller electrodes. Then, seam welding is performed on the laminate by successively repeating an ON/OFF operation of a conduction state between the pair of roller electrodes while moving the laminate relative to the pair of roller electrodes. When the seam welding stops in a state where the pair of roller electrodes are unpowered and then the seam welding is to be resumed, the laminate is moved by a predetermined distance in a direction opposite to the relative moving direction during seam welding, spot welding is performed on the laminate, and then the seam welding is resumed.

Shifts of a reference point C in a robot coordinate system among three postures of a seam welding apparatus 10 are found, and calibration data is obtained (STEP 1). Correction data is found from the calibration data based on deformation of elastic units 22a due to weight of the seam welding apparatus 10 in accordance with the posture of the seam welding apparatus 10 relative to a robot 20 (STEP 5). Teaching data is corrected based on the correction data (STEP 6).

Shifts of a reference point C in a robot coordinate system among three postures of a seam welding apparatus 10 are found, and calibration data is obtained (STEP 1). Correction data is found from the calibration data based on deformation of elastic units 22a due to weight of the seam welding apparatus 10 in accordance with the posture of the seam welding apparatus 10 relative to a robot 20 (STEP 5). Teaching data is corrected based on the correction data (STEP 6).

A welding installation with a calibration tool is provided in a device for producing container shells. The force exerted by the container shells on the calibration tool is measured and evaluated as information for the overlapping width of the respective container shell. This allows adjusting the calibration tool during configuration of the device and allows the removal of container shells welded with too large or too small overlapping during production of container shells.

A welding installation with a calibration tool is provided in a device for producing container shells. The force exerted by the container shells on the calibration tool is measured and evaluated as information for the overlapping width of the respective container shell. This allows adjusting the calibration tool during configuration of the device and allows the removal of container shells welded with too large or too small overlapping during production of container shells.