With the increasing level of welding automation, ensuring that the welding torch remains precisely aligned with the groove centre has become a key factor limiting the quality of automatic welding. During manual welding, the welder relies on the naked eye to observe the arc and molten pool and adjust the torch position. However, an automatic welding device without a feedback system will deviate from the weld seam when workpiece fixturing errors or welding thermal distortion occur. Jiangsu Haizhongzhou Shipping Industry Co., Ltd. has fully equipped its automatic welding equipment with seam tracking systems, giving the welding torch a pair of “eyes”.
Seam tracking systems are mainly divided into contact and non‑contact types. Contact tracking uses a guide wheel or probe that rolls inside the groove, with a displacement sensor detecting changes in the groove position. The signal is fed back to the control system to adjust the lateral position of the torch. This method has the advantage of strong anti‑interference capability, unaffected by arc light, smoke and magnetic fields, and is suitable for fillet welds and lap welds. Haizhongzhou uses contact tracking on the welding robots of its sub‑assembly production line for fillet welds, achieving tracking accuracy of plus or minus 0.5 mm.
Non‑contact tracking is primarily laser vision tracking. The laser sensor projects a structured light onto the workpiece surface, and a camera in front of the torch captures images of the laser stripe modulated by the groove geometry. Image processing algorithms calculate the centre position, width, depth and cross‑sectional area of the groove in real time. Haizhongzhou widely uses laser vision tracking on submerged arc welding and electrogas welding equipment. The operating wavelength of the laser sensor is typically 660 nm or 808 nm, and with a narrow‑band filter, arc light interference can be effectively filtered out. The tracking response speed exceeds fifty times per second, maintaining precise torch centring even at high welding speeds.
For single‑sided welding with backing that achieves double‑sided formation, the seam tracking system can also detect changes in the root gap. When the gap exceeds the process window, the system automatically adjusts the welding current and wire feed speed, or triggers an alarm to alert the operator for intervention. After upgrading the automatic welding equipment with seam tracking systems, Haizhongzhou has kept the deviation during welding within 0.5 mm, significantly improving weld bead uniformity and reducing lack‑of‑fusion and arc‑off defects by more than sixty percent.
Commissioning the seam tracking system is also a technical skill. Haizhongzhou has established a tracking parameter library for each combination of weld type and plate thickness, including laser exposure time, filter threshold, tracking gain and response speed. The operator simply selects the workpiece type on a touchscreen, and the system automatically calls up the corresponding tracking parameters. It is this pair of “eyes” that has freed automatic welding equipment from blind welding and achieved truly intelligent operation.
