Metrology for Automated Hull Layout

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Project Participants: General Dynamics Electric Boat

Project Start: October 2008

The significant number of hull attachments that are fabricated and later installed on each hull contribute significantly to the cost and span time for outfitting Navy warships, particularly submarines. Each attachment or penetration may entail only a modest effort in its own right, but there are thousands of such attachments on each submarine thereby making the cost substantial. This General Dynamics Electric Boat (GDEB) project successfully identified and is now implementing several applications where metrology technologies can be used to further automate the layout and attachment process.

The GDEB team investigated advancements to several metrology technologies including internal GPS (iGPS), laser trackers, total stations, and a 3D measuring arm. Three of the four technology advancements proved to be very effective in performing the assigned tasks based on their versatility and mobility. These three technologies are well suited for the manufacturing dynamics at the GDEB-Quonset Point facility and will be implemented. The iGPS technology, though accurate, required significant setup and breakdown times, potentially reducing the overall cost savings. The three technology advancements to be implemented (Laser Tracker with the I-Probe and T-Mac, Targetless Total Station, and a ScanShark ROMER Arm) will provide the following benefits: (1) the resulting early layout event allows GDEB to establish an as-built condition of each hull cylinder; (2) operations that were performed at different intervals in the vertical or horizontal outfitting stages can now be performed at the single cylinder level; (3) early layout allows the trades to work without interruption or without having to wait in queue for individual layouts to be performed; and (4) the as-built three-dimensional grid model of the single cylinder aides the trade personnel with cylinder pairings. It is expected that the use of these tools will have a significant impact on overall cost and schedule of the VIRGINIA-Class Submarine (VCS), saving an estimated $475K per hull.

Findings from this project are applicable and beneficial to construction activities at other major shipyards. Improvements to this methodology are not limited to submarines, but are applicable to aircraft carriers and other surface combatants.

Metrology for Automated Hull Layout is a follow-on effort to the previously completed and very successful CNST/ManTech project, Laser Image Projection. The GDEB team discovered that image projection technology could automate layout processes for attachments, thus significantly reducing the labor hours and span times and eliminating the use of antiquated paper templates and string measurements. This project continued to focus on hull attachments by investigating additional metrology technologies and applications for their use.

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