The larger the component, the smaller the batch size. This is typically the case with heavy-duty machining in many branches of the industry. In fact, this provides as much of a challenge to wind turbine engineering and the production of large commercial vehicles as it does to the railway industry. Many of the very large components are not only produced in small batches, but are also expected to be produced with the highest quality. Existing multi-stage, unnecessarily complex production processes do not work in favor of these demands, because every re-clamping of the workpiece represents an inherent danger to process integrity and component quality. The multi-functional VLC production centers from EMAG follow a totally different and more efficient approach in heavy-duty machining. Workpieces of up to 1,200mm diameter and a weight of 1,500 kg are machined vertically, in a single set up, and on one machine that accommodates a number of different machining processes and includes automation.

Heavy-duty machining is booming. Wind turbine construction in China and Europe is one industry that is responsible for this boom, another is the increasing output of commercial vehicles in almost all relevant markets, from South America to Asia. According to the foreign trade experts at Germany Trade and Invest (GTI) Brazil's production in HGVs rose by over 12 percent during the first half of 2011 compared to the same period the previous year. In China, the production of HGVs tripled from 2009/2010. The railway construction industry of some countries also has a chance at considerable growth. For instance, the GTI estimates that Russia will be investing over 85 billion Euro in its railway system before they host the soccer world championships there in 2018.

What do these industries have in common when discussed in the context of heavy-duty machining requirements? Whether we are talking planetary gear carriers for wind turbines, brake discs for commercial vehicles, or railway wheels, the demands are very similar. Components must pass several complicated quality test because all these parts will be exposed to extreme stress when in service. Take a wind turbine, for example: it is in service for an average of 120,000 hours and exposed to varying wind conditions for 20 or more years. But its production must be flexible, despite relatively small numbers; and the production tools used should be adaptable for the machining of other components, without complex conversion work.

Meeting the requirements of heavy-duty machining with the help of a compact production system concept is not an easy assignment. Many companies use complex, interlinked, multi-stage processes to machine large workpieces. The VLC production centers from EMAG, however, rely on a totally different approach. Not only do the machines load themselves, with the help of a pick-up spindle, but the machining area accommodates all necessary machining processes, turning, drilling, milling, grinding, gear hobbing, on the same machine, and in a single setup. To accomplish this, the production center is equipped with an automatic turning tool receptor, milling spindle and tool changer. The single set up ensures dimensional accuracy and a constantly maintained, excellent surface finish.

At the top of EMAG's range of heavy-duty machining centers is the VLC 1200. It handles workpieces up to 1,200mm diameter and 1,500 kg in weight. "Despite having to handle these enormous components, the production center displays the same qualities as all the vertical pick-up machines from EMAG," explains Markus Woitsch, Business Unit Manager Application Engineering. To be able to explain the success of the VLC machines in the heavy-duty machining circles it is important to take a closer look at the basic construction of this machine series. The spindle carrying the workpiece is positioned vertically above the tool, which allows the chips to fall unobstructed into a conveyor located below, from there they are transported out of the machining area. This prevents the hot chips from heating up the workpieces and contaminating the workspindle. "This is a great advantage especially in a lightly-manned, fully automated, heavy-duty machining environment," confirms Markus Woitsch. Another successful feature of this kind of heavy-duty machining is the quality control. Sourcing of the raw-parts is where the heavy investment starts; mistakes made during the production process would result in high and unnecessary costs. The answer from the designers of the VLC series to this challenge is highly sophisticated one: a probe with an accuracy of 2µm measures and checks the workpieces in-between machining operations.

Some of the advantages of the VLC are explained by the following two application examples:

One manufacturer uses an EMAG VLC 500 in the production of components for the nacelle of a wind turbine. Batch sizes are approximately 120 per week. Production of the six different components calls for up to 12 different tools. "These numbers show the flexibility of the machine. Without time-consuming modifications, the VLC 500 is capable of machining a number of totally different constituent components," emphasizes Markus Woitsch. "Furthermore, the wind turbine specification calls for a particularly high degree of component quality, which we can guarantee with the VLC."

An EMAG VLC 1200 that complete-machines railway wheels and brake discs has to carry a weight of three metric tons, including the chuck at the spindle nose. The production center also incorporates a chain magazine for 36 tools. High feed rates in the X- and Z-axes of the work spindle and a maximum torque of 13,000 Nm lead to short throughput times. "This enormous amount of power, the integral pick-up automation and the intelligent combination of diverse machining applications in a single set up have enabled us to reduce throughput times by up to 80 percent, compared to previously used processes," confirms Markus Woitsch.

The advantages of a multi-function concept have a positive effect also on the production of components for construction machinery, HGVs and agricultural machines. Compared to the traditional shop floor production of such components on three or four machines, the work load is reduced significantly when there is only the VLC to set up. "It makes a big difference whether I have to set up three or four machines for the production of 10 components, or just one," explains Markus Woitsch.

One of the determining factors in the success of the VLC series, over a hundred of these machines are already being used worldwide, is their modular design. Every machine is configured to suit the user's particular production requirements. There are many possibilities: one or two turrets, the integration of the grinding and hard machining processes and the different workpiece capacities of the VLC 500, VLC 800 and VLC 12200.