"Advanced Metalworking Solutions for
Naval Systems that Go in Harm's Way"
Improved Manufacturing Processes Reduce Distortion and Enhance Producibility of Submarine Weapons Cradles
Applying DFM improvements will reduce manufacturing costs for VCS weapons cradles that hold torpedoes (shown above) on the ship. US Navy photo
Virginia Class (SSN 774) Submarines (VCS) use weapons cradles to handle weapons shipboard prior to launch from the torpedo tubes. General Dynamics Electric Boat (EB) and Newport News Shipbuilding (NNS) have encountered significant issues maintaining the very close dimensional tolerances for this long, thin structure manufactured with extensive welding. Any rework or scrapping is very costly to the program. The objective of this Navy Metalworking Center (NMC) project is to improve the producibility of weapons cradles.
In April 2012, the Integrated Project Team (IPT) received written authorization from the VCS and Tomahawk Program Offices; Naval Undersea Warfare Center (NUWC), Division Newport; and the Technical Warrant Holders for Shock, Launcher, and Torpedo programs to proceed with drawing development and fabrication of a prototype improved cradle weldment. The improved cradle weldment configuration includes multiple design for manufacturability (DFM) improvements, including consolidation of multi-piece subassemblies into single-piece construction; design for mechanization to incorporate an improved opposing-arc welding process; and elimination or reduction of post-process operations such as machining, pressing and stress relief. A 4-head opposing-arc submerged arc welding process has been developed for making the 20-ft welds in a single pass with no back gouging. A full-scale prototype is being constructed in the fall of 2012.
Implementation and Technology Transfer:
NNS has implemented some incremental cradle process improvement recommendations such as using a balanced weld joint for the sidewalls, gas metal arc welding spray process for the outer sidewall seam welds, having a dedicated team for cradle manufacturing and using spacers for precambering the bottom plate. EB and NNS are executing an engineering request to implement the major recommendations beginning with one-piece end blocks and balanced weld joint in 2013 on SSN 786 cradles. The remaining collective improvements will be implemented on SSN 789, with a possibility of implementation on SSN 788 in 2014.
For more information, contact:
Dr. Daniel L. Winterscheidt
NMC Senior Program Director