In a clear statement that pneumatics technology is not the only field in which it excels, Festo has released an electrical drive that allows positioning axes cycle times of 10 ms and working strokes exceeding 5 m.
The new DGE-RF toothed belt drive seems set to become the flagship electrical drive from Festo on the back of its performance and specifications, as well as its resistance to external ambient influences. Gentle and barely audible, the drive is smooth running and quiet thanks to the roller guide technology. The device is capable of rapid positioning at any desired point and can run 10 000 km between lube services, thanks to easily refillable oil reserves that do not require opening of the housing.
Festo is confident that the DGE-RF will strengthen its reputation as a supplier of electrical boom, spindle and toothed belt axes - including multi-axis solutions - as well as gear units, servo-motors and stepper motors with regulators and positioning controllers.
Electrical drives extend the motion control options offered by Festo. The choice between pneumatic, servo-pneumatic and the various electrical drive types depends upon several operating criteria. For example, pneumatic drives are capable of withstanding high duty-cycles, great loads and even overloading. They are available in a wide variety of sizes and variants. Equipped with appropriate sensors and valve technology, pneumatic components match some of the characteristics provided by controlled drive technology through being freely positionable. Where a rapid build-up of force is required (servo-motors, etc) electric drives can be advantageous, enhancing accuracy, controllability and load rigidity.
Different Festo solutions for different applications
Due to the conversion of energy to produce compressed air, the effective energy cost of pneumatics is increased. However, pneumatic components and their control loops are always less expensive to procure than electrical drives and controllers. The ruggedness, simplicity and reliability demonstrated by pneumatics reduce maintenance and troubleshooting expenses. In addition, pneumatic drives provide additional functions, such as guides, adaptation options and sensing.
As an alternative to standard pneumatic and electrical drives, servo-pneumatics allow for speed and position controlled motion, as well as accurate, dynamic positioning. Such a solution normally comprises a pneumatic cylinder with integrated displacement encoder, one proportional valve and a positioning controller, such as Festo's SPC200.
When filling yoghurt, ice cream, mustard, spinach and other viscous food products, the strengths of servo-pneumatics truly come to bear. Food products are metered and filled in a single work step - namely, volumetric filling. Servo-pneumatics are flexible to this end - they allow for variable programming of required volumes, and the filling speed can also be matched to the product and everything can be controlled via a fieldbus.
The containers are filled with precisely the right volume of product, without splashing. The food product is drawn into a measuring cylinder from a reservoir. The length of the stroke during reverse travel determines the volume. The product is then pressed into the container during the forward stroke. The user programs the desired parameters (volume, measuring and filling speed) in his controller and loads them directly to the positioning controller, or selects them from predefined parameter lists. Volume control is made variable, flexible, remote controllable and fully automatic with servo-pneumatics.
Servo-pneumatics feature accuracies of 0,2 mm with typical strokes of 100 to 2000 m, thus exceeding typical filling requirements. Accuracies of 0,1 mm can be achieved with electrical toothed belt drives, which is only minimally influenced by the length of the drive. Electrical spindle drives offer the highest levels of accuracy, but wherever accuracy is not of utmost importance, where dynamic performance (acceleration of up to 30 m/s2) and large loads (2 to 300 kg) are required, when the machine's design offers very limited space, where difficult ambient conditions prevail and where price is important, servo-pneumatics are a good alternative.
Festo offers users a choice of pneumatic, servo-pneumatic and electrical drives, but selection is based upon the respective application.
For more information contact Richard Teagle, managing director, Festo, 011 971 5500, richard_teagle@festo.com, www.festo.com
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