Let's go into reverseAugust 2006Need to redesign a component and lost the original drawings or CAD data? Don't worry, there's quite a lot out there to help you 'reverse engineer' that component and establish its new CAD identity If you need to replicate a part but have lost the drawings or produce a mould tool from an existing component, then you should be taking a look at what's on offer in terms of reverse engineering software and systems. Let's take Delcam's CopyCAD (www.copycad.com) as a starting point.
Most reverse engineering software requires the user to create a surface model from scan data before work can start work, say, on a tool design. The latest release of CopyCAD offers a range of triangle modelling tools that allow mould cores and cavities to be generated directly from triangle models, saving an enormous amount of time. The secret is in the way CopyCAD generates horizon lines on the model, which produces smoother curves by applying a user-defined angular tolerance. This avoids those jagged split lines that might otherwise be produced from the triangle edges. Delcam says that once a curve has been created, developments in triangle splitting mean that dividing large or complex models can be up to ten times faster.
A couple of months ago at an exhibition in Germany, ICEM (www.icem.com) demonstrated a new reverse engineering and surface modelling workflow environment in conjunction with project partner, Konica Minolta. ICEM's existing reverse engineering software, RevEng allows the efficient handling of 3D digitised data, imported as individual points from tactile measuring devices, as point clouds or facet data from laser scanners, or from photogrammetry (measurements taken from photographs) systems. Once imported, the software displays the data as rendered images and then converts them into surface models for subsequent refinement. Incidentally, Goss Innovations (www.gossinnovations.com) operates a photogrammetric modelling system, which is useful on those occasions when obtaining 3D measurements is either very difficult or impossible due to access limitations. Architects are particularly fond of this reverse engineering approach.
TranscenData's (www.fegs.co.uk) CADfix - more usually applied to the translation and repair of customers CAD data - also has a reverse engineering role. Apparently, the software comes into its own when the STL files (obtained from triangulating the point cloud data) need to be processed - something at which CADfix is very efficient. The package can also be used to take the surface borders and node positions of 'old' mesh data to regenerate IGES style data that can be re-meshed as required.
OK, so much for the software, but what about getting the data in the first place? I've already touched upon the three main methods: tactile systems (essentially co-ordinate measurement machines), laser scanning devices and photogrammetry.
Northern Technologies (www.filetranslation.co.uk) will undertake this for you using its recently acquired MicroScribe (www.microscribe-digitisers.co.uk) 3DX digitiser, which is a tactile device. The company can produce 3D surface point clouds or curves and then convert these into an IGES surface model that will run on virtually any leading CAD software product.
Collaboration between servo system specialist, Unimatic (www.unimatic.co.uk) and the UK's premier metrology specialist, Renishaw (www.renishaw.com) has seen the development of an integrated scanning/cutting system that brings together Unimatic's affordable CNC milling machinery range and Renishaw's digitising probes and software. Unimatic claims that this combination can 'dramatically' simplify the scanning and machining stages of the reverse engineering process.
Actually, there is yet another way of obtaining a digital image of an object, and one that quite a lot of us will be familiar with from a clinical point of view - computed tomography (CT) scanning. This process uses X-rays that penetrate an object from many different directions, the results of which are analysed by a computer program to reveal the object's fine internal structure. Systems like this can be expensive and it is often wiser to 'farm out' such work to a specialist agency. However, if your work involves repetitive CT scanning for, say, research purposes, then a company like X-Tek (www.xtekxray.com) might be able to help.
X-Tek can provide CT systems as small as its 'Linx', to 50ton/450kV walk-in rooms, and if nothing from that range suits, then the company will build one that does. The 3D point cloud data produced by the technique can be output as a stereo lithography file, which is accepted by most CAD packages. Once imported into CAD, the radiographic information can be used to create a new CAD file for rapid prototyping and reverse engineering.
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