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MDA Technologies 5/2014

MDA Technologies 5/2014

Drive technologies the

Drive technologies the closer they can be positioned to the actuator. Here, Aventics is setting new standards with its AV valve generation: In contrast to conventional valves, the diagonal design halves the required space. The AV03 valves are as small as a credit card. At the same time, the use of high-performance plastics reduces the weight by around 50 %. The compact design also has an effect on the pilot valve technology. Compact pneumatic valve systems have special electropneumatic pilot valves that convert the output signals from electric controls into pneumatic control signals for the main valves. Miniaturization in industrial pneumatics creates new challenges for pilot valve technology to provide the same switching times and performance in a considerably smaller space. Other actuator principles are inefficient During the development of the new valve generation, engineers at Aventics quickly decided to exploit the potential of conventional electromagnetic converters even further. After thorough testing, they discarded the idea of developing new actuator principles. The main reason: Alternative technologies, such as Piezo valves with boosters, increase manufacturing costs to a level that the market cannot support. The six basic requirements for flow rate, dynamics, efficiency, size, service life, and New valve generations by Aventics Aventics shows the potential for further development of conventional electromagnetic converters in the new AV series valve generation in the sizes AV03 with a nominal flow of 300 Nl/ min and AV05 with a nominal flow of 700 Nl/min. Here, the electromagnetic converter has been reduced to a few cubic millimeters while maintaining high flow rates of 300 and 700 Nl/min. costs had top priority when drawing up the specifications for the AV series and downsizing the electromagnetic converters to just a few cubic millimeters. To stick with the credit card comparison, the aim was to achieve dimensions for the AV03 that would be just above the size of a chip on a credit card. Ball with hard seal In the new AV series valve generation, Aventics uses a pilot valve cartridge with electromagnetic actuator in a U-bracket design. The pneumatic control unit has a cartridge design and is easy to integrate in a main valve. The pneumatic control unit of the valve cartridge has a dramatically different design compared to other common market solutions. Whereas conventional pilot valves use elastomer discs to softly seal against ring-shaped seats, the Aventics valve cartridge has a hard seat. The control element is a metal ball that seals in an injection-molded, cone-shaped plastic seat. The valve cartridge consists of less than 15 individual components. The separate miniature components, such as the seal seat for the air supply or the pressure piece for force transmission are made of plastic and have a size of only around 10 mm³. This also places high demands on the component tolerances and precision in the production process. In order to achieve fast switching times, it is not enough to simply reduce the size and mass. In fact, tribological factors come into play to reduce friction as well. Aventics can fall back on decades of experience in the use of optimized slide bearing systems in pneumatics that are based on both highperformance plastics and metals. During the production of the valve cartridges, various laser welding processes are used for metals and plastics, as well as thermal processes. Flow rate improved by 40 % Thanks to its special shape, the pilot valve can be easily integrated in the main valve and enables an optimized design for the pneumatic channel guiding. Engineers reduced energy-guzzling swirling by improving geometries and providing flatter angles for the supply and exhaust channels. In comparison with common valves, this increases the flow rate by around 40 %. The practical result: the valve system operates at a working pressure that is 15 % lower than before thanks to a smaller pressure drop. Current reduction during the holding phase The reduction in size also has an effect on the actuator. Reducing the available winding space in the solenoid leads to a corresponding decrease in magnetomotive force. This lowers the force potential, which results in a less efficient ratio of friction to useful force. As a result, engineers have to draw up a more sophisticated design during configuration. Besides a reduction in force potential at a specified performance level, a reduction in size also leads to a less-favorable thermal situation due to smaller surfaces for heat transfer. Aventics is counteracting these issues with an intelligent control strategy. As the electromagnetic actuator only has a high need for current during the pull-in phase, the current can be greatly reduced during the holding phase. This enables considerably lower solenoid power dissipation, particularly for long duty cycles, and improves the thermal situation. Since it makes sense to use the described control strategy directly on each valve, only minimalist electronic circuits are possible, due to space and cost restraints. However, the power dissipation in the electronics themselves is the decisive assessment criterion, as this portion reduces the useful output and has a negative influence on the thermal balance. Here, the new AV series valve generation offers an intelligent solution that also takes the energetic aspects of market demands into account. Conclusion Miniaturization of conventional pilot valve technology fulfils the demands of modern pneumatics: it efficiently provides the required output and long service life at market-driven prices. This will ensure that pneumatics still has an important role to play in industrial applications of the future. Photographs: Aventics GmbH About Company name: Aventics established: 2014 (formerly Bosch Rexroth Pneumatics) Turnover: € 400 m Employees: : 2,100 globally Products: industrial pneumatics, marine industry, tooth chains, commercial vehicles 42 MDA Technologies 5/2014

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