New on the Techdrives website (www.techdrives.co.uk) are high speed linear actuators drive by electric motors with output speeds up to 635mm/s. Electrical operation gives a more controllable alternative to hydraulics and pneumatics, without leakage problems, and easier to integrate into machine systems. Options are ac, dc and servo motors, and strokes are available in increments of 100mm from 100 to 800mm.
These high-speed actuators are manufactured by linear motion specialist Servomech. Construction is in a ‘U’ configuration where the motor is connected to a ballscrew by a timing belt and pulleys. The pitch of the ballscrew allows different rated speeds. Encoders for precise control of speed and position can easily be added either to the actuator housing or as part of the motor. The result is a compact design that is also efficient with running efficiencies around 70%.
There are five sizes in the UBA range of high speed actuators. The smallest model fitted with a dc motor has been used as a door actuator delivering a force of 85N at 635mm/s from a 4 amp 24 volt motor. The closed length for 100mm stroke is only 365mm. In the middle of the range a model UBA2 is used for diverting baggage on airport conveyors. A force of 1800N is produced at 110mm/s with a frequency of 1400 operations per hour. The largest model in the range, the UBA4, can achieve 3000N at 265mm/s powered by a 1.1kW ac motor.
As these UBA actuators are based on ballscrews, the duty cycle can be as high as 100%. Motors can be ac or dc, but for the highest performance and control servo motors are ideal. With the highly dynamic forces and reversible ballscrews, encoder feedback to a controller is normally necessary together with brakes on the motors. Optimum selection and installation requires consideration of factors such as buckling loads and critical speeds. Lenze Engineers at Techdrives have the necessary experience and expertise to advise on machine designs.