Making Light Work of Heavy-Duty Machining
By Oliver Hagenlocher
Director of marketing
EMAG Sales and Services GMBH
The larger the component, the smaller the batch size—this is the way one could describe the demands made on heavy-duty machining in many branches of manufacturing. In fact, this simple equation provides as much of a challenge to wind turbine engineering and the production of large commercial vehicles as it does to, for instance, the railway construction industry.
Many of the very large components are not only produced in small batches, the relevant market participants are also expected to produce them at the highest quality. Existing multistage, unnecessarily complex production processes do, however, not work in favor of these demands, as every re-clamping of the workpiece represents an inherent danger to process integrity and component quality. There are, however, multifunctional VLC production centers that take a totally different and more efficient approach in heavy-duty machining. Workpieces of up to 1200-mm diameter and 1500 kg can be machined on them vertically, in a single setup. Only a single machine need be involved, one that accommodates a number of different machining processes and includes automation.
Industries with a Need for Speed
Heavy-duty machining is booming. The factors responsible for this are the big success of wind turbine construction in China and Europe and the ever-increasing output of large commercial vehicles—both those that run on and off tracks—in almost all relevant markets, from South America to Asia.
According to the foreign trade experts at Germany Trade and Invest (GTI)—the German federal agency that promotes foreign trade and investment—Brazil’s production in Heavy Goods Vehicles rose by over 12% during the first half of 2011 compared to the same period the previous year. (A Heavy Goods Vehicle [HGV] is a freight vehicle with a gross combined vehicle weight greater than 3500 kg.) In China, the production of HGVs tripled in 2009/2010. The railway construction industry of some countries also holds great promise of considerable growth. For instance, the GTI estimates that Russia will be investing over €85 billion in its railway system before the country will hold the 2018 FIFA World Cup soccer championship.
What do these branches of manufacturing have in common when viewed in the context of heavy-duty machining requirements? Whether we are talking planetary gear carriers for wind turbines, brake disks for commercial vehicles, or railway wheels, the demands made on the different production planners are very similar. Component quality must pass the severest tests, as all these parts will be exposed to extreme stresses 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 and weather conditions for 20 years or more. But its production must be highly flexible, despite relatively small numbers; and the production tools used ought to be adaptable for the machining of other components, without involving complex conversion work.
Machining Workpieces of up to 1.5 t
Meeting the requirements of heavy-duty machining with the help of a compact production system concept is no matter of course. Many companies use complex, interlinked, multistage 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 achieve this, the production center is equipped with an automatic turning tool receptor, milling spindle and toolchanger. The single setup ensures a high degree of dimensional accuracy and a constantly maintained, excellent surface finish.
At the top of the range of heavy-duty machining centers is the VLC 1200, presently the world’s largest pick-up machine. It handles workpieces of up to 1200-mm diameter and 1500 kg. “Despite having to handle these enormous components, the production center displays the same qualities as all the vertical pick-up machines from EMAG,” said Markus Woitsch, business unit manager, Application Engineering.
To be able to explain the success the VLC machines are enjoying in 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 unhindered into a conveyor located below, from where they are transported out of the machining area. This prevents the hot chips from heating up the workpieces and contaminating the spindle.
“This is a great advantage, especially in a lightly-manned, fully automated, heavy-duty machining environment,” said Woitsch.
Another benefit derived from this kind of heavy-duty machining is the quality control. The raw materials used for this type of workpiece represent a heavy investment. Mistakes made during the production process result in high, avoidable costs. The VLC series’ designers came up with a very sophisticated response to this challenge: a probe with an accuracy of 2 μm measures and checks the workpieces between machining operations.
Some of the advantages of the VLC as used in various areas of manufacturing can be seen in these two applications:
- One manufacturer uses a VLC 500 to produce 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 already show the flexibility of the machine. Without time-consuming modifications, the VLC 500 is capable of machining a number of totally different constituent components,” said Woitsch. “Furthermore, the wind turbine specification calls for a particularly high degree of component quality, which we can guarantee with the VLC.”
- A VLC 1200 that complete-machines railway wheels and brake disks has to carry a weight of 3 t—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 workspindle and a maximum torque of 13,000 N•m make for short throughput times. “This enormous amount of power, the integral pick-up automation and the intelligent combination of diverse machining applications in a single setup have enabled us to reduce throughput times by up to 80%, compared to previously used processes,” said Woitsch.
Setting Effort and Process Control
The advantages of a multifunction concept also have a positive effect on the production of components for construction machinery, HGVs and agricultural machines. Compared to the classical shop floor production of such components on three or four machines, the work load is greatly reduced when one has only the VLC to set up. “It makes a great difference whether I have to set up three or four machines for the production of 10 components, or just one,” explained Woitsch.
Another telling feature of the VLC series is their modular design. Every machine is configured to suit the user’s particular production requirements. The possibilities are many: one or two turrets, the integration of grinding and hard-machining processes and the different workpiece capacities of the VLC 500, VLC 800 and VLC 1200.
This article was first published in the 2013 edition of the Energy Manufacturing Yearbook.
Published Date : 12/6/2013