Two prototype (preproduction) weld seam facing tools, which were developed under a Navy Metalworking Center (NMC) project, were recently delivered to Bath Iron Works (BIW) and Northrop Grumman Shipbuilding-Gulf Coast (NGSB-GC). These tools will greatly reduce or eliminate the need for manual grinding of certain weld reinforcements on the DDG 1000 class of ships.
The butt welding of exterior ship panels produces a weld protrusion that exceeds DDG 1000 fairness requirements. As a result, approximately 23,000 feet of weld reinforcement would have required manual hand grinding to bring the weld flush with the hull. The manual weld removal is slow, which increases shipbuilding costs, and the repetitive nature of hand grinding causes frequent injuries (e.g., carpal tunnel, eye, back) and costly medical expenses. The cost savings from using weld seam facing technology for removal of butt welds alone on DDG 1000 is estimated at $750,000 per hull.
The preproduction tools remove the weld automatically at a minimum rate of 20 feet per hour versus the current rate of three feet per hour. The tool is capable of removing the majority of weld reinforcement height with minimal or no further hand grinding. The preproduction tools now at BIW and NGSB-GC will enable the shipyards to begin to take advantage of their benefits, identify potential tool enhancements for future production tool acquisitions and identify other processes that can leverage this technology. Currently, a modified version of the tool is being considered for back-gouging and welding.
The NMC project team consists of BIW, NGSB-GC, General Dynamics Electric Boat, Naval Surface Warfare Center-Carderock Division (NSWCCD), DDG 1000 Program Office (PMS 500) and PushCorp, Inc. NMC developed and validated the weld seam facing tool concept, and PushCorp, Inc., designed and manufactured the preproduction tools and is in the process of commercializing the product. The shipyards and NSWCCD provided technical direction and support to help ensure implementation.