Cover story: Forward in reverse

The process of reverse engineering has a long history. It was perhaps first industrialised into an engineering process during the post-World War II era as the US frantically tried to figure out how German rocket technology worked for military advantage. More recently, after a Red Bull Formula One racing car crashed at a recent Grand Prix, it was hoisted up to reveal its underbody diffuser. The photos taken were no doubt then studied by engineers at competing teams as they entered in to a reverse engineering process to try and figure out, how it works, how it's made and just why it gives superior performance. As a result of these activities, reverse engineering is often associated with negative connotations and perhaps people often think of military or commercial espionage, copying of patents, copyright infringements and intellectual property theft. However, reverse engineering actually has a perfectly legitimate place in the modern design process and is a technique that is gathering pace and popularity. "We tend to call it virtual prototyping, or digital prototyping, which is basically extracting characteristics from competitive products and using that as a basis to improve your own design," says Professor Mark Williams, deputy head of Warwick Manufacturing Group's digital theme technologies. "Obviously intellectual property rights (IPR) are in place and still there, and you most definitely can't copy things that are covered by patents. However, you can often take physical characteristics such as internal and external geometry and convert that in to working CAD models, which can improve the design process." The premise of reverse engineering is almost like a benchmarking exercise. You are assessing the 'best-in-class' product, understanding what makes it 'best-in-class' and then trying to gain a competitive edge. This approach is widely used in the automotive industry, where companies often freely lend each other cars to facilitate it. There are generally a number of stages involved, but the first is capturing geometry, which can be achieved using a variety of techniques and technologies, from touch probe coordinate measuring machines (CMM) to laser scanning, photogrammetry and CT scans. Scanning a component or part produces what is known as a point cloud. These are essentially millions of individual points in space that define the geometry of the part that has been scanned. However, to go from a point cloud to a workable CAD model that can be manipulated, edited, and added to, takes a lot of time and effort. Post processing of point cloud data is a highly skilled, time-consuming and laborious task which is generally why it has been outsourced to experts, who go through the points and remove the 'noise', missed and duplicated points, of which there are literally millions. "Once you have a clean working cloud, you can then create a .stl, surface file," says Professor Williams. "You triangulate all these individual points to get a surface. But, you can't really use that for anything – it is just a load of tessellated triangles in space. The really clever part is actually cleaning that surface file to get it in to a workable format where you can actually use it in whatever application you want." To get a simulation model from a clean surface file is more straightforward, as the tessellated surface model is very closely related to that of a finite element mesh. However, the difficulty comes when the production of a full parametric CAD model is required. "Rather than starting from a blank sheet of paper, you have got a parametric model based on something that works in the market place," says Professor Williams. "This process saves so much time and can then be used as a basis for moving a design forward and improving upon it." This is not, however, something that requires high investment and a tool only available to multinational OEMs with large design budgets. Like most things in life you get what you pay for, and this is reflected in the accuracy of the scans that will be produced. But, portable and cost effective solutions are available and can quickly and easily produce a point cloud of a component. Geomagic's specialises in providing reverse engineering and 3D inspection products to industry and supports this with professional services and consultants. They have seen the industry grow tremendously in recent years as the cost of scanning technology and computer processing power has reduced. It has seen steady progress over the last 10 years in point cloud processing and reverse engineering software, aided by two recent breakthroughs. First has been the ability to capture and reproduce what it refers to as 'design intent' of a physical object. Design intent modelling extends reverse engineering from simply producing an accurate digital copy of a scan by automatically identifying primitive shapes, swept features and freeform surfaces. This ability to generate CAD ready surfaces from scans of physical objects has laid the groundwork for another significant development; a technology dubbed by Geomagic as 'Parametric Exchange'. Parametric Exchange is essentially a software bridge from the point cloud to a CAD model. It enables the automatic reconstruction of geometry such as parametric surfaces, data and curves without the need for intermediate neutral files such as IGES or STEP. Geomagic's Rachael Dalton-Taggart says: "Imagine you want to design a bike handle grip or something similar. It would make sense to scan in an existing one – of course making sure you are not infringing on someone else's IP – and use that as a basis for a design; a starting point. Why start from scratch and try to reinvent the wheel when there is something there already? Being able to very quickly turn a physical part in to a 3D model gives you such a head start in product design." This closed loop between scan data and CAD models gives product designers and engineers the freedom to explore endless variations of products. It also has the potential to save in tooling costs. For example, instead of recreating an expensive mould from scratch, companies can scan an existing one, analyse the wear and tear, design an improved model, and manufacture new moulds in days instead of weeks or months. Such a system is also useful for capturing design geometry such as natural shapes. For example, a new hand grip for a bike could either be designed towards a specific demographic – younger children for example – or indeed to custom fit a specific person. And this has great potential for medical applications. Dalton-Taggart says: "Prosthetic limbs at the moment are generally generic devices that are not going to fit everyone with equal comfort. To be able to do a scan of an existing joint and very quickly produce something customised would be a tremendously powerful tool. "Custom mass manufacturing is definitely out there on the horizon, and it is because of these technologies. At some point we will be sending a scan of our feet to shoe manufacturers so the shoes are custom fit." The ability to capture an existing design and quickly adapt it to new styles and purposes is critical in the evolution from mass manufacturing to mass customisation. These tools will go some way to delivering on the promise of individualised design on an affordable, mass scale, basis. The process also finds a lot of use where rare or one off parts need to be recreated. Work at WMG has seen the technology used by archaeologists to reverse engineer rare artefacts, and also with the British School of Rome for a rare statue head. But more industrialised uses of this same concept are being applied to firms that have lost CAD data, designs or drawings, or which have inherited tooling from buyouts or takeovers. Old parts which have failed or need replacing can be scanned and this can then be used to see where the wear is on the surface, for example. Essentially this allows digital inspection of old parts to be assessed for wear and tear in some detail. Through that, finite element analysis can be run, and then it is possible to re-engineer the part to improve it. Reverse engineering has numerous uses and roles to play in the design and engineering process, from taking a best in class product and using it as a baseline for product development, to saving time modelling what is essentially standard geometry. Of course, good judgment is essential when analysing and assessing competitor products, but it is a tremendously powerful tool that is definitely moving design forward.