The disadvantage of the resistance spot welding is that the reproducability of the weld quality is not guaranted due to the variation of many correlated weld parameters in process. Thus resistance spot welding requires and on line control through closed loop control system in order to assure the homogeneous quality of the weld joints.
During the nugget formation of the resistance spot welding, the generated heat cause thermal expansion of the sheet metal which forces the electrode to move apart. This phenomenon is called electrode movement.
In this thesis, the relationship between weld quality and electrode movement is investigated preliminary and varified experimentally that the electrode movement can be used as a control parameter. Proportional algorithm is employed to generate control input signal through the microcomputer as a control algorithm. The effectiveness of the spot welding control on the weld quality is evaluated by comparing the uncontrolled one through the shear strength test.
