Semiadaptive synergic-fill welding tractor for ship unit erection

At most U.S. shipyards, the bottleneck for improving productivity is unit fabrication and ship erection. Fit-up during unit, super-unit, and ship erection is difficult, resulting in variable gap and mismatch, which promote defects and repair. A semiadaptive synergic-fill welding tractor was developed for improving the productivity of seam welds during erection. The tractor has many features that advanced robots have but is simple to use because it relies on operator pass planning instead of robotic path preplanning. The synergic-fill welding concept was developed to maximize the deployment of robust welding procedures. This was a new control process for making changes to weld bead size during fabrication using one knob. The synergic-fill welding concept was developed for flux-cored arc welding of DH36 steels for horizontal erection seams. These seams have a range of gap and require a range of weld bead sizes to uniformly fill the weld seam. Welding parameters that ensured a constant base metal dilution were optimized and programmed into the synergic control. In addition, the welding tractor was developed with a laser seam tracking vision sensor and adaptive-fill control. The new control allows the operator to intervene during welding and toggle the adaptive features on and off. A special four-axis tractor was developed to permit cross-seam and torch height control for seam tracking while oscillating the welding torch. The laser sensor was integrated with modular fixturing to permit welding with either angled or transverse oscillation. The adaptive control algorithm varied the weld size from the synergic-fill starting point that was selected by the operator. The weld bead was made proportionally larger or smaller as the joint width became larger or smaller within the process capability range. A semiadaptive control algorithm was developed for the horizontal welding application. The process was not completely automatic. The operator, who plans the position of the welding torch for each weld bead in a layer, applies the process. Further, he made weld bead size decisions based on the joint width. Once the welding system was started, it tracked the bead location as the groove width changed, controlled the torch height, and can adaptively vary bead size relative to joint width. This flexible technology will minimize the susceptibility to defects during erection welding.