FORAN, efficient at early design stages

14/08/2013
FORAN, efficient at early design stages

The design, production and operation of ships need to be understood as an overall business from the beginning, when the major decisions are made. Many of these decisions are the result of estimates or based on known data from previous projects. The more accurate these estimations are, the better results obtained in terms of costs. If it is possible to have the aid of tools to create the ship 3D model at early design stages, simple but accurate enough, benefits will be collected downstream.

SENER has provided FORAN, a shipbuilding CAD/CAM system, with the necessary capabilities to ensure its efficient use at early design stages. Some remarkable capabilities are based on the total integration between all ship design stages and disciplines, the use of topology and tools to facilitate seamless transition to the detail design stage. Benefits are an easy evaluation of design alternatives, management of modifications, full control of the integrity of the information and quality, all in a collaborative design environment.

FORAN philosophy

The FORAN solution is based on the integration of all the design stages and disciplines, thanks to a single database, which moreover permits the implementation of collaborative engineering and guarantees the information integrity.

The main advantage of the topological definition, where geometrical data are not stored but calculated on-line, is that changes in the main hull surfaces are automatically incorporated in the modified elements, just by reprocessing them.

The solution delivered by FORAN includes tools that facilitate the direct transition from basic to detail design, by means of simple operations that include blocks splitting, the assignment of parts to blocks and the completion of the model with attributes for the manufacturing phase.

Basic Design Process

The basic design process in FORAN begins with the forms file definition, hydrostatic calculations, definition of volumes, characterization of the intact and damage stability conditions and other naval architecture concepts. Later on it is necessary to define the material catalogues describing plates and profiles to be used in the design.

Once the hull forms, decks, bulkheads and other surfaces are created, the hull structure module is used to create the major openings in all surfaces, the scantling of the main surfaces for plates and profiles as well as the main structural elements.

  • Surface definition and naval architecture calculations

FORAN has two complementary tools for surface definition, including the external hull forms, decks, bulkheads, appendages and superstructures. The surfaces can be imported from files using different generic formats.

The use of topology makes possible the automatic recalculation of all elements when a modification is performed, producing important time savings.

Once the surfaces have been defined, it is possible to analyse the hydrostatic and stability calculations. SENER has developed a new module called FBASIC that groups in a single solution the former modules.

  • Volume definition

The module FGA (FORAN General Arrangement) deals with the definition of the compartments and arrangement of a ship. A 3D model of the spaces will be generated taken as reference the surfaces of the ship as well as auxiliary planes. It is also possible the definition of spaces from 2D drawing in a specific environment. Compartment arrangement defined on FGA will be available in FBASIC module for hydrostatic and stability calculations.

  • Early 3D model of structure

The hull structure definition at early design stage is made in the same environment in FORAN that will be used later for the detail design stage.

High productivity tools allows the efficient definition of the hull structure model, like one-click plate definition, reduction to the minimum of the auxiliary geometry and join and split functions for plates and profiles.

There is a context for the generation of 3D curved surfaces, allowing the quick definition of plates, profiles and holes.

Thanks to the topology, the definition of the shell and deck plating can start in the early stages of the design, even with a preliminary definition of the hull and decks. Flat and curved plates are represented as solids (including thickness) and the information for plate pre-development is automatically generated allowing thus an early material take-off list.

Profile definition is mainly based on topological references to already existing structural elements, as well as to auxiliary concepts used in the early stage of the design (longitudinal spacing, frame system, other profiles, etc). The user can easily assign different attributes such as material, scantling and web and thickness orientation. These basic attributes can be completed by adding constructive attributes (parametric web, flange end cuts, etc) at any time of the design process. The profiles can be split up in profile parts later. Profiles crossing other profiles will automatically generate the necessary cut-outs and scallops.

Another context in FORAN allows the internal structure definition. This environment provides a set of advanced functions for the easy definition and modification of plates (flat, flanged and corrugated), straight and curved stiffeners, holes, face bars, standard plates, on and off plane brackets, collars and others.

It is possible to have several sections in memory making easy operations, like copy or multiple editions of elements in different sections.

  • Outfitting & electrical initial design

Consists of two parallel processes completely linked one to each other: the initial definition of the main systems as logical diagrams, for piping and for electrical connections, and the positioning of the most relevant items within the 3D model of the ship.

In both cases and applying the same unicity principle, the items are defined once although can be represented several times. Items being equipment, fittings, pipes, cables... they all are added to their corresponding project master list, with all the needed data, from where they are retrieved later to be part of a diagram (as a symbol) or part of the model. Weight, power demand, volume, connections and other attributes are there to get any kind of report and calculation. Logically any update in the attributes is propagated downstream to the diagrams, the 3D model, the material reports and the calculations.

The spatial positioning of the equipment can be referred to the initial surfaces and to the frame system, so further modifications on such entities (yet foreseen at this early stage) would affect to the equipment automatically, similarly than to the structure. Once again the topology allows a fast generation of different alternatives regarding the ship arrangement.

  • Generation of outputs from the 3D Model

The drawing generation in FORAN is managed by a single module, which covers the output drawings of all design disciplines, completely user configurable. Drawings are generated directly from the 3D product model. The 2D entities that represent the product model are linked to the 3D elements and are always updated with the latest version.

The possibility to reprocess the drawing after changes in the model it is very useful, and at the same time keeping any manual modifications introduced by the user in the drawing.

Classification drawings for approval are the main outputs that can be extracted from an early ship 3D model. Other important reports that can be obtained are weights and centre of gravity, painted areas, material take off lists, bill of materials and welding lengths.

Link with Finite Element tools

FORAN incorporates a link that makes possible to export a simplified ship model, leveraging its topological characteristics. Functional algorithms allow the generation of an intelligent model, simplifying, filtering and deleting unnecessary data to guarantee the quality of the model transferred.

Transition to detail design

The reuse of information is critical in the process. FORAN allows a smooth transition to detail design, providing tools for subdividing and joining plates and profiles, and also features additional attributes for detail design such as bevelling, construction margins and shrinkage factors, and also for defining parts that are not relevant during the basic design stages.

The level of detail not only concerns geometry but also attributes. Part attributes irrelevant in conceptual stages become critical in detail design. In order to provide a smooth transition, tools to modify, check and copy attributes of large groups of pieces are provided.

The block subdivision is perhaps one of the most critical points in ship design regarding the transition between design stages. Although split and refinement tools can be used for block subdivision, some specific tools are provided in order to perform automatic recalculation of parts when the block butts are modified. Assignment of parts to units can be done at any time by means of a powerful graphical selection tool.

As a summary, benefits for the early generation of a ship 3D model in FORAN are: shorter evaluation of different design alternatives, early estimation of materials and weights, including welding and painting, less risk of inconsistencies, easier link with analysis and calculation tool, quick position of the most relevant equipment and seamless transition to detail design based in the reuse of data which reduces the design time and simplifies the overall process. -the end-

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