Converting the pneumatic- to servo-based system in resistance spot welding: analyzing the dissimilar weld joints for two welding schemes

This experimental investigation analyzes the performance of two types of electrode-actuating systems, pertaining to welding current increments in resistance spot welding. Alternating current (AC) waveform, 75 kVA apparent power and C-typed body frame of a welding machine are engaged to undertake the entire experiment. Initially, the pneumatic-supported compression technique is employed to weld the dissimilar combinations of metal sheets; the carbon steel and stainless steel in this case. Since the pneumatic cylinder consumes reasonable amount of time to operate, it is limited to handle the single-periodic AC waveform which is designated as the single current and single force (SISF) welding scheme. As the pneumatic-based system is mechanically redesigned and refitted for the servo-supported compression, thereafter it paved ways to manipulate the compression variables as to support the dual current and dual force (DIDF) welding scheme in addition to the original SISF welding scheme. After the successful attempts for both schemes, the welded samples underwent the tensile test, hardness test, post-crack pattern recognition and finally subjected to the metallurgical observation to characterize the differences and anomalies. The result shows that the weld formations have been greatly improved in servo system for the SISF and DIDF compared to the pneumatic SISF welding scheme.