A no-indentation welding monitoring device may include a pressing force measuring device for measuring a pressing force for pressing a welding target of a welding tip of a welding gun, a voltage measuring device for measuring a voltage applied to the welding tip of the welding gun, and a monitor device for digitizing a welding quality by use of the pressing force and the voltage transmitted from the pressing force measuring device and the voltage measuring device.

A resistance spot welding method comprises: performing test welding; and performing actual welding after the test welding. The test welding is performed under each of two or more welding conditions. In the actual welding, preliminary current passage is performed by constant current control in the same current pattern as in the preliminary current passage of the test welding, an electrical property between the electrodes in the preliminary current passage in the actual welding and an electrical property between the electrodes stored in the preliminary current passage in the test welding are compared for each welding condition to set a target in main current passage in the actual welding, and thereafter adaptive control welding is performed to control a current passage amount as the main current passage.

The present invention relates micro resistance welding apparatus and to a method of welding. In particular, the present invention relates to small scale or micro welding apparatus and to a method of micro resistance welding using a controlled sequence of current, voltage and/or power signal profile for an electric arc. The invention provides a welding apparatus comprising: a controller supplying a controlled drive current to a weld head circuit in which the controller supplies said controlled drive current in dependence upon electrical feedback from the weld head circuit and in which the controlled drive current is defined by a sequence of segments and for each segment the welding apparatus operates in a mode defined by setting one of a predetermined current target, a predetermined voltage target or a predetermined power target; and at least two of the segments are operated in a different mode from one another. The invention also provide a method of operating such an apparatus.

A resistance welder controller controls a welding current flowing through an inverter transformer, detects the welding current flowing through the inverter transformer, measures an energizing time and a point time interval of the detected welding current, calculates a usage rate of the inverter transformer using the energizing time and the point time interval, stores an equivalent current curve indicating a relationship between a current value of the welding current and the usage rate of the inverter transformer when the inverter transformer is operated at a rated capacity, and determines whether a relationship between the current value and the calculated usage rate of the inverter transformer exceeds the rated capacity of the inverter transformer based on the equivalent current curve, continues an operation when the relationship does not exceed the rated capacity of the inverter transformer, and stops the operation when the relationship exceeds the rated capacity of the inverter transformer.

A resistance welding apparatus includes a welding tool with a welding electrode configured to contact a component. A welding transformer is configured to feed an electric current to the welding tool and a control device is configured to control a polarity of welding transformer by transmitting polarity information to the welding transformer such that a polarity of the welding transformer is switchable. A circuit including two transistors is operably connected in series between the welding tool and an output of the welding transformer and a polarity one of the transistors is rotated relative to the other transistor, such that a polarity of a welding voltage at the welding electrode is switchable with the switching of the polarity of the welding transformer, and such that a polarity of a welding current at the welding transformer is switchable with the switching of the polarity of the welding transformer.

A stored time variation curve and cumulative amount of heat generated of each step are each used as a target. In the case where a time variation of an instantaneous amount of heat generated per unit volume differs from the time variation curve in any of the steps, a current passage amount is controlled in order to compensate for the difference within a remaining welding time in the step so that a cumulative amount of heat generated per unit volume in actual welding matches the stored cumulative amount of heat generated in the test welding. Further, in the case where expulsion is detected in any of the steps, then in subsequent welding, the cumulative amount of heat generated per unit volume used as the target is reduced, and the current passage amount is adjusted in accordance with the reduced cumulative amount of heat generated per unit volume.

Provided is an evaluation system including: an analog-to-digital converting section comprised of a programmable circuit and configured to convert an analog signal, the analog signal being acquired by a physical quantity acquiring section and indicative of a time-series change of at least one of (i) welding current, welding voltage, or load applied to pieces to be welded and (ii) a displacement, during welding, of a welding head; and an evaluating section configured to determine, based on a digital signal, whether or not the time-series change satisfies a predetermined condition, wherein configuration data for configuring the programmable circuit is arranged to be changeable by a user.

An example apparatus to monitor a welding-type system includes: a test signal generator configured to output a test signal to a monitored circuit; and a lock-in amplifier configured to: receive a reference signal based on the test signal; measure a leakage current in the monitored circuit based on the reference signal; and generate an output signal representative of the leakage current.

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.

Methods and apparatus for detecting a leakage current are disclosed. An example apparatus to monitor a welding-type system includes: a test signal generator configured to output a test signal to a welding-type circuit; and a lock-in amplifier configured to: receive a reference signal based on the test signal; measure a leakage current in the welding-type circuit based on the reference signal; and generate an output signal representative of the leakage current.