Symmetrical transition waveform control on double-wire MIG welding

To reduce unsteady and undercut phenomena during double-wire MIG welding process, a symmetrical transition waveform control method, which was based on analyzing the effect of the electromagnetic force, was proposed. A symmetrical transition period was added when the welding current was switched between peak value and base value. Three variables were introduced, which were leading transition current I_SL, double wires transition time T_s and trailing transition current I_ST. Corresponding experiments were conducted to compare the different phenomena between employing this period and not employing the period. Orthogonal experiments were conducted to study the influence by the three variables. An optimum combination of I_SL, T_s, I_ST could be obtained by means of range analysis, and corresponding experiments verified the combination. All the experiments showed that the symmetrical transition period can reduce the large variation of welding current, make the welding process steadier and the welding seam much more polished, and obtain welding seam with higher quality.