Improved Manufacturing Processes Reduce Distortion and Enhance Producibility of Submarine Weapons Cradles

Process Improvement:

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.

Expected Benefits:

• EB and NNS estimate cost savings of $60K per cradle or $1.1M per submarine shipset. Total savings for the VCS program over five years is projected to be $11M.
• Reduced rework and scrap costs
• Improved schedule by 30 percent