Lasers light a better way to build a sub

Hank Hogan, hank@hankhogan.com

By using laser projection instead of paper and string, an estimated half a million dollars could be saved on every Virginia-class submarine hull built by the General Dynamics Electric Boat Div. in Quonset Point, R.I. That adds up to tens of millions of dollars in construction cost savings for the planned fleet of attack submarines.

Development of the technique was funded by the Office of Naval Research (ONR), based in Arlington, which has been looking to develop and deploy advanced manufacturing techniques in shipyards. The new laser projection technology automates what had been a manual task of transferring drawings onto a hull, said Quentin Saulter, manager of the ONR Directed Energy Program.

“The projection system moves the lasers in a seamless fashion to project templates or lines on walls,” he explained.

He added that the technique could have applications in the construction of airplanes, buildings and silos. Other large construction projects also could potentially benefit from the technology.

Virginia-class attack submarines run 115 m long and are 10 m at their widest point. During hull construction, thousands of electrical and ventilation hangers must be located and attached to the proper point. There also are thousands of studs that must be installed.

Laser image projection will help in building the Virginia-class nuclear-powered attack submarines, such as the one shown here under construction by General Dynamics Electric Boat. Using lasers instead of the traditional paper templates and string will save an estimated $500,000 per hull. Courtesy of US Navy.

Conventionally, this has been done through the use of paper templates and string; for example, construction workers use string to measure where various attachments should be made, then the templates to determine the precise location and orientation of each attachment. This manual approach consumes significant time, with the burden made greater by the need to build in checks to eliminate human error.

Looking to automate the process, the ONR funded the development of a laser projection system that can replace the paper and string. Saulter noted that the curved shape of a submarine makes this task easier because a laser beam can actually wrap around the entire cylinder.

The projection system that was developed has been tested and is now being deployed in manufacturing. The enabling technology is not the lasers, which can be the standard solid-state variety, but instead, computer control of the lasers, which must be fast enough to move the images seamlessly around on command. That requirement for a quick response also means that the controlling computers must have enough capacity to hold all of the construction plans in memory. Recent advances in technology have made it possible for systems to meet both criteria.

The laser projection approach should have some 7700 man-hours of work, and the automation could result in an 85 percent reduction in labor, as compared with the traditional method. Ultimately, production workers will have direct access to the ship’s computerized construction model, Saulter said.

“The CAD [computer-aided design] models would actually drive the laser images, saving steps by making templates and diagrams of where fasteners need to go on walls,” he explained.