Method for controlling the position of welding electrode in arc-welding with weaving

Claim 1

In a method for controlling the position of a welding electrode in arc-welding with weaving, which comprises: directing a welding electrode substantially vertically toward a groove formed between objects of welding; continuously moving said welding electrode along the line of said groove while reciprocating said welding electrode in the width direction of said groove; feeding, on the other hand, a welding current to said welding electrode to produce an arc between the tip of said welding electrode and said groove to weld said objects of welding together along the line of said groove by means of the arc heat; continuously detecting values (I) of one of arc current and arc voltage of said arc during said welding; continuously calculating deviations (I-Io) of the thus detected values (I) from a previously set reference value (Io) of one of arc current and arc voltage for each one reciprocation of said welding electrode in the width direction of said groove; continuously calculating, relative to the vertical plane which passes through the center of amplitude of said one reciprocation of said welding electrode and is parallel to the line of said groove, a representative value (L') of left-side deviations (L) of said deviations (I-Io) and a representative value (R') of right-side deviations (R) of said deviations (I-Io); continuously calculating the difference (L'-R') between said representative value (L') of said left-side deviations (L) and said representative value (R') of said right-side deviations (R); and, controllably aligning the center of said amplitude of said one reciprocation of said welding electrode with the center of said groove in the width direction thereof so that said difference (L'-R') becomes null; the improvement characterized by: storing said left-side deviations (L) and said right-side deviations (R) at prescribed time intervals, said time intervals being in the range of from 1/1000 to 1/4000 second; calculating at said prescribed time intervals when said welding electrode moves over the left side of said groove relative to said vertical plane, differences (L-R) between said left-side deviations (L) at said prescribed time intervals during said left-side movement of said welding electrode, on one hand, and said stored right-side deviations (R) at said prescribed time intervals during the immediately preceding right-side movement of said welding electrode over the right side of said groove relative to said vertical plane, on the other hand; and controllably aligning the center of said amplitude of said one reciprocation of said welding electrode with the center of said groove in the width direction thereof at said prescribed time intervals so that said differences (L-R) become null; and, calculating at said prescribed time intervals, when said welding electrode moves over the right side of said groove relative to said vertical plane, differences (L-R) between said right-side deviations (R) at said prescribed time intervals during said right-side movement of said welding electrode, on one hand, and said stored left-side deviations (L) at said prescribed time intervals during the immediately preceding left-side movement of said welding electrode over the left side of said groove relative to said vertical plane, on the other hand, and controllably aligning the center of said amplitude of said one reciprocation of said welding electrode with the center of said groove in the width direction thereof at said prescribed time intervals so that said differences (L-R) become null.