Flexible linear electric actuators for harsh environments
09 May 2012
Festo has introduced a range of electric piston-rod cylinders with enhanced ingress protection up to IP65. The new enhanced IP versions of DNCE cylinders are available in 32, 40 and 63mm frame sizes and with standard stroke lengths from 100 to 800mm in 100mm steps, depending on size. All the cylinders employ a high performance ball screw drive and are capable of handling acceleration rates up to 6m/s/s.
Each model offers a choice of two spindle pitches, enabling users to select the optimum drive characteristics for their needs, and each actuator achieves high positional repetition accuracy of plus or minus 0.02mm.
Unlike pneumatic cylinders, where there is always a positive internal pressure to help protect against the ingress of moisture, standard electric cylinders are inherently more susceptible to corrosion when used in wet environments, due to the suction effect of their internal drive mechanism. This tends to limit their potential as alternatives to pneumatic cylinders. The enhanced IP versions of the DNCE cylinder overcome this disadvantage, widening their applications scope significantly.
The main improvement to the enhanced IP versions of the DNCE is a threaded breather port in the front face of the cylinder, which enables users to connect a length of standard pneumatic tubing for the remote supply of air and exhaust venting in an area outside the immediate environment. This prevents unwanted media being drawn into the drive, resulting in increased reliability and reduced need for routine maintenance.
An optional bellow kit further extends the level of protection, by guarding against damage or corrosion of the piston rod, cylinder seals and bearings by aggressive media such as dust, chippings, oil, grease or fuel. It also helps prevent water in washdown environments from entering the cylinder. The front of the bellow has a polymer ring with a breather port that accepts a push-in tube connector, enabling air to be ducted to and from a safe environment, in the same manner as the port on the cylinder’s body.
To accompany the bellow option, Festo has introduced a piston rod extension kit that provides the extra length needed to accommodate the bellow in its compressed state. Further enhancements, all designed to simplify cylinder installation and use, include various piston rod options such as threaded extension pieces, special threads, and a female thread instead of the standard male version.
Enhanced IP versions of the DNCE are suitable for use with a range of Festo stepper and servomotors, as well as third-party products, which can be mounted in-line or in parallel using a toothed belt coupler. Unlike many IP65 rated automation products on the market , which only achieve this level of protection by the use of sealant compounds, the DNCE features motor coupling housings with full IP-rated gasket sets. These retain their protective qualities throughout the life of the product. Users can disassemble the cylinder and motor to implement changes such as altering the drive ratio or to perform routine servicing, confident that the protection level will be retained on re-assembly.
DNCE cylinders use the same types of mounting adaptors as the company’s DNC pneumatic cylinders and to a large degree are mechanically interchangeable, enabling machine builders to switch to all-electric alternatives very easily. An extensive range of cylinder accessories includes foot, end flange, trunnion and swivel flange mounting components, as well as a wide variety of piston rod attachments such as clevis and ball-end couplings.
All DNCE cylinders are constructed from robust extruded aluminium, with a high alloy stainless steel piston rod and a steel spindle. The piston rod is non-rotating and its internal drive is equipped with a collar magnet for positional feedback purposes. The cylinder housing features full-length T-slots, enabling proximity sensors to fitted at any desired position and adjusted very easily.
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