Project Number: S2751

Project Title: Automated Welding of Hull Inserts for VIRGINIA and COLUMBIA Class Submarines

Period of Performance: MAY18 – MAR24

The legacy process to install hull inserts in submarine pressure hulls is an intricate sequence of events consisting of multiple manual operations, including cutting, beveling, grinding and welding processes. The process requires extensive labor in excess of 45,000 hours per hull, and installing hull inserts significantly increases the manufacturing span time for the initial outfitting phase. Weld quality is dependent on tribal knowledge and individual skill level, thus additional rework is often required. Because this process is entirely manual, a robotic installation solution would improve weld quality and has the potential to reduce the labor required for submarine build schedules. These welds are much more complex than linear welds in a fixed-welding position. Welding parameters must change multiple times as the weld torch moves along the curvature of the hull through various welding positions. Cutting and beveling holes in the hull require constant varying of the bevel angle on the hull and the insert to keep the weld joint’s angle consistent, as the hull curvature changes around the circumference of the weld. Because of the complexities of each individual process, there are no readily available commercial off-the-shelf technologies capable of performing all of the integral steps associated with this complex process.
The objective of this Center for Naval Metalworking (CNM) project was to develop robotic cutting and welding prototypes to demonstrate the hull-insert and hull-penetration process on VIRGINIA and COLUMBIA Class submarines (VCS and CLB, respectively). The project team developed a hull-insert and hull-penetration process by leveraging previous robotic and automated technologies currently implemented at General Dynamics Electric Boat (GDEB). The solution, achieved robotically, could cut and beveling the pressure hull for placement of the insert and penetration and will weld the insert or penetration into the pressure hull. This project investigated the use of large industrial welding and cutting robotic systems in conjunction with collaborative robots for smaller inserts and penetrations, but ultimately it was decided to implement the Fanuc cobots.

Through automation and weld quality improvements, an estimated 20 percent reduction in cutting, fitting and welding labor is forecast as a result of this CNM project. Through increased efficiencies enabled by the technology, GDEB will save $1.9M per VCS/VPM hull and $1.4M per CLB hull for combined five-year savings of $17.7M across all programs
with an ROI of 1.90.

The transition event for this project is GDEB’s performance demonstration activities. Once those activities have been successfully completed, the process will have been verified to meet the expectations of the project teams and stakeholders and will be ready for implementation efforts at GDEB. Implementation is anticipated in the third quarter of FY2025.
Implementation is expected to utilize a phased approach, in which the most beneficial opportunities will be assigned a higher priority and implemented first in the production of VCS, VIRGINIA Payload Module (VPM) and CLB. The schedule for implementation activities is dependent on the project results.