Mechanical CAD can give it the large

Once people start working on large assemblies and working concurrently in databases, they suddenly see the possibilities of 3D and all the woes go away,” said Mike Gascoyne, when he was chief designer at Jordan Grand Prix. “As always, it’s getting to that point that counts.” Other critical areas for 3D are packaging (making everything fit in the smallest possible space), detailed design and avoiding mistakes. “It’s not that noticeable at the component level,” said Gascoyne. “It’s when you are working in large assemblies that you see ‘the lights come on’.” Very, very rarely is the output of any design exercise a single component, be it CAD or the sharp pencil method. Consequently, CAD software vendors have been obsessed with being able to cope with large assemblies for what seems like decades. In the mid 1990s every new release of a major CAD product was accompanied by some kind of high part count claim for assembly modelling. In the days when CAD was ‘hardware limited’ (slow speed processors and minuscule memory) there was little anyone could do but chop large assemblies into manageable chunks and hope for the best when they came to be re-united. Architectural lead Next came visualisation software. I remember reviewing CVpvs, Computervision’s Project Visualisation System, in August 1993. It was one of the first to use abbreviated (approximate) data and viewing algorithms like ‘level of detail’ (the closer you are the more parts are displayed) and ‘part culling’ (when parts are not within the viewport the system does not try to generate or display them). All in the name of helping to cope with very large assemblies and improving interaction speed. Today’s DMU (digital mock-up) software owes plenty to these early systems. They came from the AEC (architectural engineering and construction) sector where being able to visualise and ‘walk through’ a large process plant or similar on screen was essential. Also central to these systems was animated display and the ability to capture ‘walk/fly throughs’ and send them to colleagues/collaborators. It was during this period that EAI – Engineering Animation Inc. was set up. This company supplied the animation/visualisation software for a number of vendors, notably Unigraphics, which eventually bought the firm in October 2000. EAI’s Vis family of products and its flagship e-Vis for collaboration, survives today. Now that we have the relative luxury of fast processors and access to ‘silly’ amounts of memory, many of the problems associated with working with large assemblies have gone away. So much so that assemblies the size of AEC projects can be handled with relative ease using exact solid model data, and architects are now using mechanical design software to model entire buildings. The Bilboa Guggenheim Museum was designed, using Catia, by architect Frank Gehry. “Catia provides a way for me to get closer to the craft,” said Gehry. “In the past, there were many layers between my rough sketch and the final building, and the feeling of the design could get lost before it reached the craftsman. It feels like I’ve been speaking a foreign language, and now, all of a sudden, the craftsman understands me. Flat drawings of curved surfaces can be beautiful, but they are deceptive; with the system you can see how to build it.” This is an artistic way of saying that with solid modelling ‘what you see is what you get’. You are actually interacting with a virtual copy of the real thing and drawings derived from solid models are exactly right in every detail – and they are absolutely unambiguous. The architectural design and construction community is watching with interest the advanced work process improvements made by Gehry’s projects but, for him, this is only the beginning. His principal partner, Jim Glymph, has indicated higher levels of demand, not just for their current and future projects, but also for the entire industry. “The use of Catia on our projects has extended the possibilities in design far beyond what we believed was possible 10 years ago. We hope that within the next 10 years, this technology will be available for all architects and engineers,” says Glymph. Is this pointing to a merging of the disciplines, finally? Time was when the benchmarks for complex assemblies came from the automotive and aerospace industries. This is still very much the case, but also the specialist machinery makers can provide machines as complex as Jumbo jets. Imagine a newspaper printing press the length of a city block in lower Manhattan and five stories high – now that’s a large assembly. Such machines are made by KBA (Koenig & Bauer Aktiengesellschaft), the oldest printing machine builder in the world, based in Germany. According to Johannes Schaede, KBA’s vice president of engineering, “It is common knowledge that the complexity of the product and the process grows throughout its design cycle, and the influence of the first in the chain is disproportionately high. If marketing and sales force engineering into unwanted variants, we call it ‘market requirements’. Very few salesmen are able to withstand the temptation to shape the product according to their customers’ known or suspected needs. “If engineering rock the boat, to include their personal experience and taste, we call it ‘improvements’,” he continues. “The consequences of both influences are growing complexity in the last process steps. This is necessarily almost irreversible, since, due to lack of time, it is almost impossible to redo the decisions.” And he adds: “We observe therefore a derivative of the second law of thermodynamics. Without investment of effort (engineering energy) any design will end up in the maximum complexity possible (design entropy). Therefore the necessity to standardise and modularise products has to be understood and supported by all participants involved.” Because of modularisation these huge newspaper presses are never built as one single entity. They follow a stringent process plan and the product structure is linked to each individual module or unit. For KBA the assembly model allows its users to examine the origin of all manufacturing processes and predict where all the raw material will end up and what processes it must go through. Because of the need to manufacture specialist 3D components, increasingly machinery makers that traditionally fall into the AEC market are now taking up mechanical CAD systems. Inteco, another German company that makes specialist units for steel mills, bought SolidWorks because in tests it could handle assemblies in excess of 10,000 parts. However, because the software was created to handle mechanical components, Inteco kept tripping over the default spatial constraints imposed on models and assemblies – a cubic kilometer – now fixed. And now 60,000 parts The next problem was the ever increasing part count and the desire to include more and more of the native steelworks in the specialist assembly. This gave rise (potentially) to assemblies in excess of 60,000 parts, which would have caused memory problems (4GB). That was solved using the pragmatic approach of simplifying certain parts to include only their exterior envelope and using configurations so that certain components could be excluded or preferentially included. “Without the configuration function, that enables us to change the level of detail, such a project would not be feasible,” says Gerhard Reithofer, Inteco’s CAD manager. “You are continually jumping from precise detail into global detail, [but] because the configurations are connected together, the different detail steps are always consistent.” When working with the complete model Inteco uses NavisWorks, a 3D visualisation tool operating within SolidWorks. “With this system it is possible to do real time interference checking on the complete assembly and view any part from any angle,” says Reithofer. “We have a combination of tools that enables us to complete these gigantic projects three-dimensionally”. Finally though, a word of caution. Recently, a major Far Eastern motor manufacturer upgraded from a Unix to a Windows design environment, following a Corporate edict, only to find that models that used to load slowly on yesterday’s 0.5GB Unix hardware would not load at all on today’s 2GB Windows 2000 workstations. Be advised, because of the way very large models and assemblies consume and thrash memory and memory management algorithms, swapping hardware and operating systems is a lot more complicated than just moving the furniture!