Shape-searching software helps avoid wasted effort
Design engineers and draftsmen are under pressure to produce better designs in less time. CAD has helped enormously in this respect, but there is often a feeling that the parts being designed are similar to parts that have previously been designed – and that time is being wasted by ‘reinventing the wheel’. While an individual can often find a similar component design and adapt it to the new requirements, as the number of people in a design department increases, and as individuals leave an organisation and take their knowledge with them, there is a growing need for a more reliable way to identify similar components.
Going a step further, there is no reason why designers and draftsmen should not be able to search outside their own department, or even outside their own organisation. So long as a precise description or part number are known, it is easy to use a text-based internet search engine to find standard parts from suppliers that either have their own website or who use portals to present their products. But without the right description or part number, there needs to be a way for standard parts – and non-standard parts as well – to be sought on the basis of geometric features.
Fortunately, recent developments in searching technology mean that there are now several ways to search for particular shapes, either with or without the concurrent use of textual search terms.
Much of the research behind these products has come from universities, such as Princeton in the USA. Princeton’s 3D Model Search Engine has actually been online since 2001 and now offers users the choice of searching by text and 2D (two-dimensional) sketch (Fig.1), text and 3D (three-dimensional) sketch, or by comparing an uploaded 3D model with the models in the database. While the user interface is very intuitive, the system is limited by the fact that it only searches its own database.
Further research at the Purdue Research and Education Center for Information Systems in Engineering (Precise), also in the USA, is aiming to develop an internet search engine for three-dimensional shapes. This system converts a 3D model into small cubes, called voxels (volume elements), then uses complex software algorithms to turn the voxels into a simplified ‘skeletal graph’ based on ‘feature vectors’. Users select a part from the search results that are returned, and then ask the system to find a cluster of similar parts(Fig. 2). As well as working with uploaded parts, the system allows users to sketch modifications to a standard part from a supplier’s catalogue and use this as the basis for the search. According to the researchers at Purdue, engineers typically spend around six weeks per year looking for information about parts, and a shape searching tool could save as much as 80percent of this wasted time.
A private company based on the Purdue Research Park, Imaginestics, has licensed the technology and, in 2006, Imaginestics unveiled what it described as the world’s first online shape search engine, based on the Purdue technology. Now known as Vizseek, the search engine allows users to freehand sketch on-screen (using a mouse or similar input device) or upload a 2D or 3D part file (Fig. 3). Text can be added to help refine the search if desired. The system then compares the desired shape (and text) with hundreds of thousands of parts that have been made available by participating suppliers.
While the systems above can be used to search databases of suppliers’ parts, there are also search facilities available that can be used within a specific CAD or solid modelling package to enable the user to search his or her company’s own inventory of part drawings or models. 3Dsearchit, for example, has been developed by Geometric Software Solutions as an add-on to Solidworks (Fig. 4).
Two versions of the package are offered, namely a free utility that can find a similar model and search attributes, and a Professional version that additionally enables the user to browse duplicates, browse clusters, assess geometry differences and index files in mapped drives. Another shape-search add-in for Solidworks is CADfind from Applied Search Technology (AST), which is based on research and development undertaken at Aston University in the UK. CADfind operates in both 2D and 3D, enabling users to find a 2D or 3D part file either by sketching a 2D drawing or creating a simple 3D model.
The system is also said to work with complex assemblies. CADfind pre-processes (‘codes’) the geometric properties of a company’s 3D models and 2D drawings and adds them to its own database. This approach means that searches can be performed by first coding the target sketch or 3D model created by the user and then comparing that code with all those stored in the CADfind database by means of fuzzy search techniques.
Since this comparison process is computationally very fast, the system searches extremely quickly; a three-pass search – using all three views of an original sketch or 3D model – of 20000 parts is said to take less than 10seconds on a normal personal computer. As well as the Solidworks add-in, AST also offers similar utilities for DWGeditor and Autocad.
For users of Solid Edge, Smap, which has its own family of 3D solid modelling tools for use with this package, offers a module called Smartsearch (Fig.2).
CAD-independent searching
UGS has recently announced a new release of Geolus Search. Enhancements include: additional ‘geometry connectors’ that allow searches to originate from virtually all leading enterprise CAD platforms including UGS’ NX software, Catia and Pro/E; the addition of Microsoft SQL Server to the list of already supported database platforms (Oracle, MySQL, and DB2); scalability and performance improvements that enable efficient searches to be made on larger databases; and improved openness with the introduction of Geolus Open, an application programming interface (API) for Geolus Search that allows third parties to build value-added applications that can leverage geometric search.
