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Abstract In an initial production planning stage, production material information in a building block is manually calculated by using data of parent ships and design experiences. Thus, the accuracy of the calculated information is low. To provide the precise information for production planning, a 3D CAD model for a hull structure is needed in the initial design stage. In this study, a hull structural CAD system, which can efficiently generate the 3D CAD model and production material information through rapid modeling in the initial design stage, was developed. The applicability of the system was verified through application to various ships. Keywords Initial hull structural CAD system; 59520
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3D CAD model; product material information. Introduction Background and Objective of This Study In an initial production planning stage of shipbuilding companies, possible processes, work sequences, and fabrication methods are determined with available enterprise resources. Production material information such as weight, center of gravity, joint length for welding, painting area, and so forth are required at this stage. And, this information must be provided as a building block unit, which corresponds to a unit of block erection under shipbuilding. The most important economic resources of the shipbuilding companies are docks and cranes to erect building blocks of a ship. If the ship is subpided and built into many building blocks on the dock, the dock occupation ratio of the ship increases, and this causes the reduction of productivity to the shipbuilding companies. Therefore, the ship is subpided into optimal number of building blocks by considering the maximum capacity of cranes. At this time, the most important thing is the accurate weight and center of gravity of building blocks. The joint length of the building blocks is needed to calculate the required man-hour to assemble and erect the corresponding building blocks on assembly shops and docks. And, the painting area of the building blocks is needed to calculate the amount of paint and man-hour required for painting process. However, it is not easy to generate accurately this production material information in the initial production planning stage. In the initial production planning stage, various design information about the position of bulkheads, number of decks, frame spacing, stiffener spacing, position of equipments, etc. are obtained from 2D drawings such as the general arrangement, midship section, lines, and so on. And then, the block pision task is performed with this information by considering the capacity of assembly shops and cranes, and by referring to the data of parent ships. Finally, production material information of each building block is roughly and manually calculated from structural parts which are included in the building block. Because the calculation task is manually performed now by using 2D drawings, data of parent ships, and design experiences, the accuracy and reliability of the calculated information is low. Besides, this calculation task is possible only for a design ship having the data of the parent ships, and is not easy for a new-build ship not having the data. The production material information can be accurately generated in the initial production planning stage, if the 3D CAD model for a hull structure is given from the initial design stage.
However, in the case of most shipbuilding companies, the 3D CAD model is generated in the detail or production design stages not in the initial design stage, because of limitation of time and lack of CAD systems supporting initial hull structural design. That is, the required time point of the 3D CAD model for calculating the production material information does not coincide with the generated time point of the 3D CAD model now. Thus, the necessity of an efficient hull structural CAD system for the initial design stage increasing. In this study, a hull structural CAD system, which can efficiently generate the 3D CAD model and production material information through rapid modeling in the initial design stage, was developed. The applicability of the system was verified through application to hull structural modeling of a VLCC (Very Large Crude oil Carrier) and a bulk carrier. Related Works Many shipbuilding companies are now making plans for performing 3D CAD modeling in the initial hull structural design stage now. However, they can not find a CAD system supporting the initial design stage, in which design changes very often arise, although many CAD systems for shipbuilding such as the TRIBON (TRIBON Solutions, 2004), IntelliShip (Intergraph, 2004), and so on have been developed. For the case of the TRIBON system, which was developed by the TRIBON Solutions several decades ago, it has been widely used in most shipbuilding companies, and much design and production experience of the shipbuilding companies was reflected in the system. Thus, the system is known as a proven CAD system for the production design stage only. However, it is reported by many specialists in shipbuilding field on a matter that design functions of the system are insufficient in the initial and detailed design stages, because of the limitations of its geometric modeling kernel, which was developed long time ago. In the TRIBON system, production material information of a building block, such as weight, center of gravity, joint length, painting area, and so forth, which is necessary for production planning, can be generated only after finishing 3D CAD modeling of a hull structure in the production design stage, in which the block pision of the ship was already decided. However, the production material information is required in the initial production planning stage, in which the block pision is not determined yet.