The welding parameters used are listed in Table 2. In comparison with Table 1, the peak current is increased from 110 to 130 A. A few parameters needed by the feedback control are added including the minimum and maximum peak periods and PE_criterion that controls the acceptance
for the vertex. The resultant weld bead for the full position test is shown in Fig. 8.The full position test results show that the weld beads produced at each position (top, side, and bottom) are smooth and consistent in width and reinforcement.Complete joint penetration is guaranteed
through the whole welding process. The measurement of the weld bead width is listed in Table 3.Although the bead widths are not the same for different welding positions, they are all acceptable for visual inspection with complete penetration. In addition, the welder/operator does not adjust welding parameters per the position during the full position welding operation. If a welding position sensor is used, welding parameters including the peak current and
PE_criterion may be further optimized to produce more consistent weld bead width despite the change in welding position.Preliminary Manual Welding With consistent complete joint penetration
obtained using an orbital welding system, a manual welding operation was also performed but only at the top position as a preliminary test. Exactly the same set of welding parameters as listed in Table 2 was used. The GTAW torch was held and moved by a human operator — an electrical
engineer with no prior welding experience — approximately 2 mm during each base period. All other welding parameters including the current, were controlled/adjusted by the monitoring and feedback control algorithm. The weld bead made at the top position is shown in Fig. 9.
As seen in Fig. 9, the novice welder did not move the GTAW torch with an identical interval each time. This is evidenced by the inconsistency of the weld bead ripples on the front side. However, with the feedback-controlled welding parameters, complete joint penetration was produced throughout the whole length of the welding operation. In addition, the weld bead
is smooth without any potential meltthrough and other discontinuities. It is believed
that with the proposed penetration control method, entry-level pipe welders should be able to produce high-quality pipe welds with guaranteed complete penetration and smooth/consistent weld
beads. Further efforts will be directed toward the full verification and demonstration of the proposed technology in manual