By employing new manufacturing technologies, this project will reduce cost and improve the producibility and first-time quality of CVN 79 weapons and stores elevator doors. (NNS Photo)
This project addresses weld distortion and fit-up issues associated with the new lighter-weight design of the CVN weapons and stores elevator doors.
Manufacturing issues such as weld distortion can have a serious impact on production schedule and cost in aircraft carrier ship construction. Relatively thin steel plates are being used to produce the CVN 78 Class weapons elevator doors and, after welding and pressing operations, the doors have not consistently met the required flatness and straightness tolerances. For CVN 79, this is being mitigated by beginning the doors earlier in the program, but the unpredictability of the weld distortion does not guarantee that the doors for CVN 79 will meet the budget and schedule targets. This project leverages work completed on the Navy Joining Center’s Control of Thin Panel Distortion Project (S2198) and improvements initially identified on a Navy Metalworking Center (NMC) Rapid Response project (R2448). The Rapid Response project addressed fabrication issues and schedule impacts, and assessed improvements in three categories: (1) current manufacturing processes; (2) Design for Manufacturing and Assembly (DFMA) design for manufacturing and assembly recommendations; and (3) alternative solutions such as mechanized welding or lower heat input welding processes. The Rapid Response project focused on making improvements to CVN 78 door manufacturing, as well as supporting CVN 79 and beyond.
In addition to developing and assessing manufacturing improvements, the project is also facilitating design for manufacturing and engineering changes that would further enhance producibility. The Integrated Project Team (IPT) will develop improved door configurations, conduct limited subscale trials and fabricate a full-scale prototype. The project is employing a prioritized approach that focuses on incremental improvements as well as an improved balanced weld configuration. The IPT will evaluate and develop several innovative manufacturing improvements, such as advanced fixturing, and will improve welding sequencing to control distortion. Improved door configurations will be developed, limited subscale trials will be conducted, and a full-scale prototype will be fabricated.
The projected benefits include improvements in cost, schedule, and quality. Over five years, the estimated cost savings of improving the producibility and first-time quality of the weapons and stores elevator doors is $5.5M.
Improvements such as removal of the back sheet, use of purchased pre-fabricated stiffeners, vertical down-welding into the door cross section, and improvements in camber compensation have been incorporated into the CVN 79 baseline design and are being validated and demonstrated for use in this project. NNS will implement additional project results on CVN 79 as doors are fabricated, beginning in 2013. NNS has qualified vertical down-welding with reduced distortion for use on CVN 79 and is fabricating a preliminary prototype door with these improvements as well as an additional machined bar and improved welding process to reduce distortion for the gasket door frame areas. Full implementation is expected to begin in April 2014 at NNS.
Naval Surface Warfare Center, Carderock Division
Newport News Shipbuilding
PMS 378 Future Aircraft Carriers