Productive Method and System to Control Dimensional Uncertainties at Final Assembling Stages in Ship Production (The National Shipbuilding Research Program).

摘要

Strict dimensional control of interim products through the different assembly stages is vitally important for profitable ship production. Studies made in Finland show that a 30% reduction in labour costs is possible in hull construction. This reduction can be gained by eliminating unnecessary fitting and reworking using tight accuracy control methods. Although accuracy control of the prefabrication stages is important because it forms the basis for the hull production, the dimensional control of the block assembling stages is essential if major improvements in productivity are to be achieved. One key problem is how to effectively organize the dimensional control of the production of large shipblocks. A modern approach is to use three dimensional (3D) coordinate measurement systems. Although these new systems provide excellent means of taking measurements, there remains a problem of applying the systems in a way that allows a straightforward interpretation of the results. The resulting interpretation should be applicable to different purposes. One objective is to meet the need of fast real time measurements on site; another is the monitoring of dimensional accuracies of different assembly stages as well as the use of the collected measurement data to improve the design and production methods. This paper presents a method for dimensional control of block assemblies. The dimensional control is thereby separated from the positional control of the block. The method is a 3D-coordinate based approach relative to a positional reference system. Also described is a real dimensional control case and an evaluation of different measurement technologies in performing the proposed task. The evaluation is made comparable to a system study performed at the National Steel and Shipbuilding Co. (NASSCO) Shipyard, San Diego, USA.