Precision sensing of arc length in GTAW based on arc light spectrum

This work aims to improve the measurement accuracy of arc length using the arc light at a particular wavelength during gas tungsten arc welding (GTAW) with argon shield. To this end, the effects of welding parameters on spectral distributions were studied. To verify the effects of base metal and arc length, the arc column was also sampled horizontally as layers for spectral analysis. Results showed that intensity of argon atom lines is determined by arc length and is independent of variation of welding conditions. Based on these findings, a compact arc light sensor has been developed to measure the arc length with a narrow-band filter (wavelength: 696.5 nm; half-width: 15 nm). Control experiments showed that the arc length was controlled with an accuracy of ±0.2 mm for the arc length in the range from 0.5 mm to 5 mm.