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NX permits advanced machining processes that lower production costs while building in quality
The rail business is growing and that’s a fact. According to the UK Government’s Office of Rail Regulation, approximately 1.2 billion passengers traveled by train in 2006-2007, an increase of 7.5 percent over 2005-2006. Freight traffic also is up, and capital investment in locomotives and rolling stock continues apace. It is now possible to travel directly from city center London to city center Paris in just two and a half hours, in perfect comfort, at speeds of over 180 mph, avoiding the stresses of airport shuttles, check-in queues and air traffic control delays. Indeed, all over the world, major new rail projects are taking shape, running on track systems designed and manufactured by Balfour Beatty Rail Track Systems using the NX™ digital product development solution from Siemens PLM Software.
Balfour Beatty Rail Track Systems Ltd has a 150-year history and is an international leader in the design and manufacture of high-quality standard and special trackwork, switches and crossings for main line, mass transit and light rail systems. Part of the £7.5 billion turnover of Balfour Beatty plc, which comprises four business sectors, Balfour Beatty Rail Track Systems operates from eight UK sites and employs 700 people.
Lionel Heinke is senior design engineer at Balfour Beatty Rail Track Systems and was responsible for the company’s implementation of NX. He says, “We adopted CAD over ten years ago, starting with two seats of Applicon Bravo and subsequently progressing to NX with Designer, Assemblies, Strength Wizard and CAM.” Explaining the application of NX, Heinke says, “Turnouts are used to guide trains from one line to another and are safety-critical products where performance and reliability are affected by axle loads and traffic type (freight, passenger, line type, train speed etc.). Crossings can be of fixed construction, where the nose and wing rails are held rigidly together, or they can have movable elements. For example, in swing-nose crossings, the wheel transfer from nose or point to wing rail or vice-versa is achieved in a similar manner to that of a conventional switch or point.” According to Heinke, “The result is a smoother wheel transfer and lower impact forces. This is particularly important at high speeds and for minimum noise and vibration.”
Heikne notes, “We have to produce designs that are safe, strong and reliable with low maintenance requirements. For example, bolted assemblies can be a particular problem area requiring frequent maintenance intervention. To reduce the need for this, where possible we have eliminated them, evolving the design of our crossings away from a fabrication to a single block of machined steel, V-shaped in plan.” Heinke points out, “We have put many years of development into the design of these components, assemblies and products, including the interface with actuation mechanisms, detection interlocks and all other necessary components. We also manufacture products to Network Rail designs and standards where there is no design work involved. However, it is in our export markets where we capitalize on our special trackwork design and innovation capabilities.”
Explaining the design process, Heinke says, “On receipt of an inquiry, we will sketch the outline or conceptual designs. This may not involve NX at all, though if we want to evaluate an idea or a specific feature or component we will use it. It’s when we achieve contract award that the detailed design work really begins. That’s when we start to use NX Designer and NX Assemblies.” He describes the process, “Generally, each project is led by one experienced engineer who deals with all aspects of design management. We have nine design engineers working individually or in teams, some dealing with contracts and some with product development.”
Turning to the actual benefits of the company’s NX strategy, Heinke says, “Drawing production is now much quicker, since we produce drawings directly from the NX model. Even though we use 3D models to generate our NC programs, we still need detailed drawings with views, sections and dimensions to relay design intent to production, QA and the customer’s inspectors. We also need drawings for assembly at the works and for installation into track.”
Heinke notes, “The forces generated when fast and heavy rail vehicles change direction can be immense and we need to be able to predict how our components will react to this. To do this, Balfour Beatty Rail chose two seats of NX Strength Wizard, a straightforward and easy-to-use analysis tool that is now part of NX Simulation Process Studio. We use Strength Wizard to mesh and analyze components to ensure they will be strong enough for the purpose. We sometimes use an external consultant to carry out a final and detailed analysis, but we have reduced the amount of work he needs to do.”
The biggest impact of NX has been on the actual manufacturing process itself. Machining rail components is a tough job, as Heinke explains, “In order to provide a smooth and reliable wheel transfer, the vees and switch blades must be progressively and accurately tapered over a considerable length. However, rolled rail sections are made from high strength, heat-treated steel with high surface hardness. We have lots of hard metal to remove and once machining starts, the rail relieves itself and subjects the fixtures to very high forces. Components can be huge, too, up to 37 meters long for switch blades and 7 meters long for crossing vees. To handle these items, we have made a multi-million pound investment in machines tools, with two very large and very powerful Henri Liné CNC gantry milling machines, one with a 20-meter bed and the other with a 29-meter bed. We also have several conventional three-axis mills.”
“To maximize the use of these expensive assets, we need to create and test our CNC programs offline,” Heinke says. “We evaluated NX CAM and some of the independent suppliers of CNC software for functionality and compatibility. We chose NX CAM for a number of reasons. It really does integrate seamlessly with the NX model. NX CAM generates programs directly from our models and where we have to make modifications, we change the model and the program updates accordingly. Heinke points out, “Material costs are very high, so we don’t produce prototypes. We manufacture directly for installation, so parts have to be right, first time. To ensure this happens, we use NX CAM toolpath verification to ensure that the part will be machined correctly, avoiding fixture clamps, for example.”
Heinke believes that NX CAM has driven the development of new and advanced machining processes at Balfour Beatty Rail. He explains, “In our industry, a lot of machining is done using specially-made shape tools. These use special inserts to generate fixed shapes that are then machined all the way though the switch rail. Special tools can cost up to £3,000 each and inserts may only last for a couple of machining hours. Using NX CAM we have developed a method that allows us to use standard tools and ‘scanning’ toolpaths to produce the required shapes. We can machine using standard carbide inserts from the price list rather than using non-standard inserts that have to be specially made. This means that our designs no longer have to be limited by our machining processes.” He adds, “We've been using this successfully on the swing-nose crossing vee monoblocks, dramatically reducing tooling costs. NX CAM has done everything we wanted it to do. We save programming time. We get a better product from a better process and this has brought us dramatic savings.”
Asked about developments in the pipeline, Heinke says, “We have been working on a strategy for using parametric modeling: geometry-driven models, large scale assemblies that are generated automatically by a sketch or numerical parameters.” He explains, “Change a parameter value and the model itself changes as do all the associated drawings. It can take weeks to design and draw a new project, even if it is based on existing geometry but with different curve radii and angles of crossing. It is not just about the physical drawing; it is about making sure that the correct-sized components, base-plates and so on, are used throughout. Using the NX parametrics capability, we are aiming to reduce even further the time to get a design to market.
“We need to do this for the business. There are great advantages to using NX when it comes to responding to tenders and there is Board level interest in its overall success. After all, we've made a considerable investment, nine seats of NX Designer and Assemblies, one seat of NX Sheet Metal Design, two seats of NX Strength Wizard and two seats of NX CAM plus lots of training. Even so, it is a relatively small investment compared to the value of the projects we are working on and compared to the benefits we are getting.”
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Client's Primary Business:
Balfour Beatty Rail has the capability, skills and proven experience to deliver total rail infrastructure services. With over 7,000 committed rail specialists, we deliver innovative and custom-built solutions in more than 30 countries to help customers meet their objectives.
"NX CAM has done everything we wanted it to do. We save programming time and we get a better product from a better process that has brought us dramatic savings."
Senior Design Engineer
Balfour Beatty Rail Track Systems
"Without NX, we would have continued with our previous expensive machining processes and been unable to develop the successful new products we have."
Senior Design Engineer
Balfour Beatty Rail Track Systems
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