The National Shipbuilding Research Program. Line Heating
NAVAL SURFACE WARFARE CENTER CARDEROCK DIV BETHESDA MD
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A product work breakdown is the framework of any shipbuilding system which features organized production lines based on the principles of group technology. Statistical control of accuracy is the means used to continuously improve a system by optimizing design details, work methods and dimensional tolerances. Line heating is the work method specifically developed to productively achieve the tolerances so identified. The three disciplines are interdependent. The key to rapid construction is how to weld without distortion . . . said Elmer L. Harm, the former Kaiser manager who directed the 1951-1961 National Bulk Carrier shipbuilding effort in Japan. Japanese managers regard that venture as the starting point of modern shipbuilding technology. Locked-in stresses produced by forces needed to fit inaccurate parts were identified as a major cause of distortion. Line heating developments followed, aimed at both achieving better accuracy when shaping curved parts and removing distortion from subassemblies immediately after their manufacture. This approach led to the development of remarkable line-heating aids and work instructions by Ishikawajima-Harima Heavy Industries IHI as described herein. In contrast traditional shipbuilders, because they are not product oriented and because they are not guided by statistical analyses, cannot fully exploit line heating. Their notion that accuracy in-process entails high costs is negated by the higher costs of dealing with distortion in succeeding assembly.
- Fabrication Metallurgy
- Marine Engineering