Studies on the block positioning metrics system for the hull erection stage

In ship hull production, the accuracy of management activities is extremely important. The block positioning operation in the erection stage is a key process in such management. The quality of the block positioning determines not only the accuracy of the final hull, but also the productivity and cost at the erection stage. We have previously proposed the basic concepts of computer-aided accuracy management. Accuracy management activities consist of "accuracy planning activities" and "accuracy measurement activities." Accuracy measurement activities involve checking and coping with inaccuracy. We have also proposed a system of accuracy measurement metrics: one is accuracy for completion (e.g., straightness, flatness), and the other is accuracy for construction (e.g., the relative joint shapes of each part). This paper explains the detailed accuracy metrics for a block positioning operation in the erection stage. The quality of the block positioning operation is estimated by this system: the accuracy of the completed hull can be evaluated by the concept of tolerance, and the accuracy of the construction process can be evaluated by the concept of labor costs. The prototype of this accuracy metrics system is then implemented. This metrics system is combined with the optimization software program iSIGHT to decide the best block positioning process. Then some examples of the block position optimizing process are shown.