Feature 4 | CAD/CAM Easier access to shipbuilding product data
Gaining easier access to product data in CAD/CAM and product lifecycle management (PLM) systems saves time and money for all stakeholders. Malay Pal, Director-Shipbuilding, Siemens Industry Soſtware explains how light-weight 3D neutral format JT can work for shipbuilding.
I
n the shipbuilding industry, CAD/ CAM systems have been a vital part of the design and construction process
for many years. Integrated CAD/CAM systems are used by many shipyards, and also often different CAD systems are used during different design stages and in different disciplines (like structures and outfitting). Besides CAD/CAM, many other soſtware tools are used by shipyards for functions like production planning and ERP (Enterprise Resource Planning). As a ship enters service, yet more soſtware tools are used for applications like configuration management, MRO (maintenance, repair and overhaul), etc. Also, the shipbuilding industry has
the involvement of a huge supply chain which includes design agents, equipment manufacturers, block fabricators, etc. Each of these organisations uses their own design systems which are oſten different from the systems used by the shipyard. Every ship project also has the involvement of owners and classification societies with whom design information is exchanged. Every CAD system has its own data format
optimised for its own functions. As a result, there are many kinds of data structures and data representation schemes. Te different soſtware tools used in ship design oſten do not communicate with each other which leads to proliferation of data, so managing a shipbuilding project becomes a very difficult task. With the expanding worldwide collaboration network which is resulting in design outsourcing, cross enterprise engineering, contract manufacture, and through life support contracts, the shipyard and its entire supply chain has to manage this complexity of communication in a heterogeneous environment. To support this, there is a need for a
product representation method which can meet the demands of application and hardware independence, support the total lifecycle of a ship, generate view
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Figure 1: What is JT?
point specific representations, and rapidly share information between geographically distributed applications and users while protecting corporate intellectual property. Te industry standard, light-weight, neutral 3D format JT along with the formalised mark-up language PLM XML provides such a platform.
JT Representations Lightweight representations are product model formats that do not include the mathematical richness of a ‘full’ CAD model. The aim of lightweight representations is to support users at different stages of the product lifecycle in rapidly browsing, retrieving and viewing product information. JT is a binary format whose data model
supports various representations of CAD geometry (Figure 1). The format can include any combination of facets (triangles
for visualisation), exact surfaces (for
• Geometry Primitives: At one of the lowest levels, simple regular geometry such as
measurement), attributes (metadata for CAD or PLM), assembly structure, and product & manufacturing information (PMI).
• Boundary Representation (BREP): BREP offers exact surface representation of the
cuboids and cylinders are located in a bounding box.
• Tessellated Geometry: Tessellated Geometry represents solids and
originating CAD system. BREP data is compressed using different algorithms and stored without data loss.
surfaces as facets. Different levels of detail (LOD) can be defined within a JT file. A low LOD means a lower level of precision, but smaller volume of data, while a very high LOD means an almost exact geometry, but a large volume of data. Te JT file is capable of
The Naval Architect January 2012
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