Patent ID: 6043449
Filing Date: 2000-03-28
Classification: B23K

Abstract:
A spot welding system comprising:a first and a second electrode adaptive for a relative advancement to each other to hold therebetween a welding spot of a work and for a relative retreat form each other to set free the welding spot;a mechanism for biasing either electrode of the first and the second electrode with a controlled pressure in a direction in which the either electrode makes the relative advancement;a power supply for supplying a controlled voltage between the first and the second electrode;a detector for detecting a variation of a distance between the first and the second electrode; anda controller for controlling a welding quality of the welding spot on a basis of a detected variation of the distance, the controller comprising:an extrenum holder for holding an extrenum of the detected variation before a spattering at the welding spot;a base setter for setting a base to be the detected variation upon a restart of a thermal expansion of the welding spot after the spattering with a continued welding current conducted through the welding spot;an adder for adding a difference between the base and the detected variation to the extrenum to provide a corrected variation;an integrator for determining a time integration of the corrected variation;an estimator for estimating a size of a nugget of the welding spot on a basis of the time integration; anda decision-maker for making a decision on a conformity of the welding quality on a basis of an estimated size of the nugget.