Merging CAD with IT.
The business of shipbuilding has traditionally been a time-consuming process, freighted with the considerable engineering challenges of designing, assembling, machining, and fitting as many as a million parts within a single structure. Most large shipbuilders rely on a range of hardware, software, and operating systems to handle legacy data and meet suppliers' and subcontractors' needs. The need to store millions of parts in various formats in disparate databases typically results in an information system that's unwieldy to manage. Even worse, such issues can introduce tremendous bottlenecks in the process of launching a new ship - and in realizing the profits from such a venture.
As if these challenges weren't enough, shipbuilders must increase their competitiveness by delivering high-quality products within compressed development schedules at very low costs. These needs are made even more urgent by the fact that the shipbuilding industry in the United States has experienced significant downsizing following the end of the Cold War and the accompanying reduction in defense budgets. Shipyards increasingly rely on their information technology (IT) systems to mitigate weaknesses and leverage core competencies. IT systems, for example, can tightly integrate design systems with business and manufacturing processes, allowing the enterprises to smoothly and quickly make the transition from design to build at a known level of risk associated with costs and schedules.
One of the oldest and largest shipyards in the world, Newport News Shipbuilding (NNS), in Newport News, Va., has launched an innovative program that leverages both off-the-shelf software as well as the company's proprietary software technology. Launched in February 1996, the program - dubbed "Full Speed Ahead" - is intended to reduce cycle times in the processes used by the shipbuilder to design and build ships.
This aggressive program is focused on various processes involved in shipbuilding such as design, production planning, material sourcing, and outfitting. Since the program's inception, NNS has leveraged its computer-aided-design, -manufacturing, and -engineering (CAD/CAM/CAE) system and IT infrastructure to successfully revitalize its engineering environment and remain profitable in a rapidly changing marketplace.
SOLID MODELS ON DEMAND
NNS engineers perform all of their ship product modeling using a proprietary program called VIVID, a design system that enables users to concurrently design structures in a multidisciplinary environment. Using VIVID, engineers design a vessel's structure, which they then use as a "background" in which to place and arrange equipment; piping; heating, ventilating, and air-conditioning (HVAC) systems; and electrical systems and cableways. VIVID's database also supports downstream activities including design reviews, drawing generation, planning and scheduling, and the preparation of manufacturing instructions.
When development began over 10 years ago, VIVID was used to design ship structures using constructive solid geometry (CSG) primitives for applications developed and run on mainframe computers. According to Mike Polini, the supervisor of software development, "The applications were suitable for visualizing the majority of the ship's structure, but they were deficient in terms of dealing with non-analytic surfaces (such as the hull) and supporting the automated manufacturing processes required by robotic cutting and welding workcells." While the system was innovative at the time, "manufacturing was poor on structure but rich in outfitting capabilities," Polini said. "Given that we could arrange all the piping and equipment, we could automatically produce drawings and instructions for manufacturing."
NNS developed an object-oriented, Unix-based version of VIVID, focusing on improved structural-design capability. Because the company had begun purchasing robots for its automated manufacturing workcells, Workstation VIVID needed to support the exchange of engineering data between designers and robots. It also had to manage manufacturing processes for plate and profile parts.
To achieve these goals, Polini said, "we needed a geometric modeler to address surface definitions, surface-to-surface intersections, curve and surface intersections, and so on." NNS selected ACIS, from Spatial Technology in Boulder, Colo., as its modeling kernel "because of its wide industry support, both in the shipbuilding industry as well as in the general mechanical CAD industry, and because of its rich functionality" he said. (For more information on ACIS, see Managing Technology, page 38.)
"We are not a traditional ACIS user," Polini added. "We do not store solid models in our database; rather, we store stripped-down representations that are more or less curves and surfaces with some attributes and features." As a design is progressively refined, localized part modifications are made by adding features using the feature-based Workstation VIVID system. based on this underlying information, each part can derive a solid model of itself, as can each feature. As a result, solid models are created essentially on demand.
"Of key importance to us is ACIS's ability to serve as our curve- and surface-modeling engine," he added. "Because of the large number of parts needed to define a model of an aircraft carrier, it is impossible to represent each part as a complete solid model. VIVID was developed to represent these parts in a more compact form based on attributed curves and surfaces with features." Because parts and features can derive solid-model representations of themselves on demand, the solid models don't need to be stored in the databases.
Although the benefits of such a system are obvious to design engineers, there are significant benefits to downstream processes as well. "At the manufacturing stage of the part's life, weld shrinkage becomes a percentage feature on the part," Polini said. "We can adjust a curve or surface by scaling it, based on a specified weld-shrinkage value." NNS engineers can determine, for instance, if a part requires a cutout in a corner, how much material will be removed by the cut, and how the assembled parts will fit relative to one another.
Because engineers' definition of a product model also can include information about how and where parts will be manufactured, users are able to route parts and assemblies through various workcells that make up the factory. Polini's team established relationships within the product model between assemblies of parts for manufacturing and the workcell - such as a cutting robot, a welding robot, or an entire robotic assembly line - that will actually do the work. Workcells can query parts or assemblies assigned to them to determine whether the designs are appropriate for processing at a given site. This capability allows NNS to proactively address potential manufacturing problems before they occur.
NNS's system ensures that the appropriate process has access to only as much information as is needed for it to go forward. Unnecessary data, which could slow down processes or make them overly complicated, aren't generated.
"Not every engineering or manufacturing process requires a solid model," Polini noted. "We can send data directly to a robot at a workcell because the robot has macro programs that recognize parameter values associated with a given part or assembly. We do not have to create a geometric representation to cut a part with the robot. Therefore, we don't degrade performance and clutter up our database will solid models that we don't need."
ACIS-enabled Workstation VIVID was implemented in late 1996 to support the construction of a series of new commercial ships. Since the first release, NNS has continued to enhance VIVID's capabilities and more tightly integrate it into the company's IT infrastructure. The delivery of several vessels using an automated steel factory driven by interfaces to NNS's modern product-modeling system is an example of the company's application of leading-edge technology to the shipbuilding industry.
"When we began building commercial ships, we committed to installing robots in our factory," Polini said. "The only way we could use the robots effectively was if we implemented Workstation VIVID to deliver data to the robots." Accordingly, when naval engineers and architects began the design of a ship, Polini's team began developing the software infrastructure to support these activities. "We loaded the definition of the parts and activities and fed the information to the robots," Polini said. "They cut the parts and put the ship together."
Throughout the process, Polini's development team stayed one step ahead of the production staff. "We made adjustments in the software to reflect adjustments in how ships would be designed by factoring in new capabilities such as robotic cutting and welding," he said. "We were doing a lot of re-engineering, software development, machine installation, and ACIS implementation simultaneously. We had just nine months to develop the software system for cutting steel. We were under pressure to accomplish a lot of activities within tight schedule constraints. If the company could not cut steel on time, we wouldn't have been able to deliver the ship on time."
Because Workstations VIVID has been tailored to the needs of ship designers at NNS, developed to support its business processes, and integrated with its manufacturing facilities, NNS has recognized reductions in engineering man hours with subsequent savings in labor costs. The organization has standardized its designs on cost-effective processes and improved the quality of its finished products.
As it looks to the future, NNS will continue to develop its IT infrastructure by harnessing the ACIS kernel. For example, NNS is using ACIS in several research-and-development projects aimed at integrating the engineering design and analysis staffs. Some of the projects include the automatic generation of finite-element meshes from product models, support for the International Standardization Organization's Standard for the Exchange of Product Data, and the generation of topological representations for compartment and zone objects.
As part of the continuing effort to develop its IT infrastructure and automate production processes, NNS has invested $60 million in upgrading its engineering design systems and automating manufacturing facilities with advanced material-handling systems, robotic cutting workcells, and robotic welding workcells. In addition, it has just begun an $80 million project to implement a shared data environment for its business systems, including planning and scheduling, material management, finance, product data management, and resource management. NNS is also transitioning its product-modeling systems from a Unix workstation environment to Windows NT platforms based on Microsoft's Activex and COM technologies. That will promote interoperability between engineering tools and office automation products, and help Newport News Shipbuilding to achieve the next level in competitiveness.
Laura Carrabine is a consultant in Pittsburgh focusing on computer-aided-design, -manufacturing, and -engineering.
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|Title Annotation:||computer-aided design; information technology|
|Date:||Jul 1, 1998|
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