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The first half of this paper reviews the significant body of work that has been devoted to understanding the fundamentals of the basic GMAW process and the use of this knowledge to develop and enhance process performance. Some of the important background studies devoted to metal transfer mechanisms are reviewed, and the tools developed to model the process and define the critical control variables for GMAW are discussed. The limitations in process performance, such as unstable transfer in low current globular, spray, and short circuit transfer modes and the perceived risk of lack of fusion in short circuit transfer, are considered. These limitations have been mitigated to some extent by process optimization based on the process models developed as well as improvements in welding consumables. Despite the limitations, it is suggested that satisfactory operation could be achieved with simple equipment and a limited number of essential control variables. Early attempts to rectify the limitations are described, but it is argued that these early innovations were restricted by the limited operating envelopes and capabilities of the original power supplies. The radical development of advanced electronic power control and its effect on extending the process operating modes is described, as are the developments in dynamic waveform control. The introduction of synergic control to enable the more complex control variables to be accommodated is also discussed. The effect of waveform control and synergic program constraints on welding procedure management is analyzed, and the advantages of improved process monitoring are reviewed. Future developments in process monitoring and control based on artificial intelligence are introduced, and a possible development to improve synergic program flexibility is suggested. Finally, the type of applications that fully utilize this ‘intelligent’ GMAW are illustrated.
John Norrish (Fri,) studied this question.