Abstract: A process is provided for producing a hollow member having a wall thickness, in a cross section orthogonal to the longitudinal direction, that varies in the longitudinal direction, the process including a heating step of heating a tubular material (Pa) so that the tubular material (Pa) is given a temperature variation in the longitudinal direction, and a stretching step of axially stretching the tubular material (Pa) that has been heated in the preceding step. In this way, a hollow member having a cross-sectional wall thickness that is variable in the longitudinal direction can be easily produced.

Abstract: A process is provided for producing a hollow member having a wall thickness, in a cross section orthogonal to the longitudinal direction, that varies in the longitudinal direction, the process including a heating step of heating a tubular material (Pa) so that the tubular material (Pa) is given a temperature variation in the longitudinal direction, and a stretching step of axially stretching the tubular material (Pa) that has been heated in the preceding step. In this way, a hollow member having a cross-sectional wall thickness that is variable in the longitudinal direction can be easily produced.

Abstract: Assuming that t1 represents a period of time until a detection signal is outputted after a sensor senses a laser beam passed through a through-hole of a workpiece, t2 represents a period of time until the detection signal derived from the sensor exceeds a preset threshold value, and t3 represents a period of time until radiation of the laser beam is actually stopped after the threshold value is exceeded, a total period of time (t1+t2+t3) of the periods of time t1 to t3 is set to be shorter than a time difference (T2−T3) between a pulse width (T3) and one cycle (T2) of a pulse signal for constructing a laser output command signal.

Abstract: Assuming that t1 represents a period of time until a detection signal is outputted after a sensor senses a laser beam passed through a through-hole of a workpiece, t2 represents a period of time until the detection signal derived from the sensor exceeds a preset threshold value, and t3 represents a period of time until radiation of the laser beam is actually stopped after the threshold value is exceeded, a total period of time (t1+t2+t3) of the periods of time t1 to t3 is set to be shorter than a time difference (T2−T3) between a pulse width (T3) and one cycle (T2) of a pulse signal for constructing a laser output command signal.

Abstract: The position of a workpiece delivered into a welding station by a feed mechanism is detected by CCD cameras of position detectors, and a positioning error of the workpiece with respect to a reference position is determined on the basis of the detected position. After training data for welding robots is corrected on the basis of the determined positioning error, scan heads on distal ends of the welding robots are inserted into the workpiece. After the scan heads have been inserted to predetermined positions in the workpiece, only the scan heads are actuated to weld the workpiece at a plurality of locations thereof with a laser beam.

Abstract: A direct-current resistance welding apparatus includes pneumatic actuators for pressurizing welding guns, respectively, to grip respective workpieces, an inverter composed of a plurality of parallel-connected switching device units each comprising a pair of series-connected switching devices, and a plurality of welding transformers connected to the welding guns, respectively, and also connected between the switching device units. A timer circuit applies an energization signal to energize the switching device units. The pneumatic actuators are actuated by a control circuit to pressurize the welding guns and successively energize the switching device units according to s sequence read from a sequence memory circuit.