The straight story on linear actuators
Linear actuators can be powered by pneumatics, hydraulics, or electric motors. Which is best for your job? Let's find out.
Belt drives
Belt drives are another method for converting rotary to linear motion. They offer many of the benefits of ballscrews, but have fewer moving parts and no critical speed limitations, for higher travel speeds with minimal component wear. Belt-drive designs, however, have lower repeatability and accuracy and often require a gearbox-fitted motor, to overcome the inertias of the load and actuator. Thrust capability is also less than that of a screw drive, because of belt tensile strength limitations.
Still, belt-driven linear actuator maintenance is generally low. Some product designs allow tensioning at the carriage. Others allow tensioning at the idler end cap of the actuator, because it eliminates the need to remove any load while tensioning the belt.
For more information, visit parker. com, or go to motionsystemdesign.com and click on Linear Motion Drives under the scrolling Component Zones bar.
Little of this, thatMany industrial machines benefit from integrating several technologies. Consider an inspection machine. The machine might use dual belt-driven actuators connected with a mechanical linkshaft for the X-axis base, for high speed and high throughput — linking the X and X' axes — and maintaining a perpendicular path for the Y axis. This also facilitates the use of electromechanical positioning for multiple points and indexing home at high speeds; it is also more cost effective than linear motors or dual screw-driven units coupled by right-angle gearboxes. The Y axes might be best controlled by slotless, linear motor-driven stages for high speed and high throughput, and high precision in the Y direction, because linear motors have no belt stretch or backlash. In this case, linear motors wouldn't have the critical speed issues of screw-driven designs. The Z axis might benefit from a screw-driven product for optical adjustment. A ballscrew plus a motor/brake unit can prevent backdrive (or free fall) in a power outage situation and can make short strokes. Linear motors are rarely used in vertical applications, because there is no easy brake solution for a power outage situation, which could cause free-falling load. Pneumatic grippers are well suited and easy to install for rotating and moving parts from one Y-axis working envelope to another. And grippers, which only need simple open and close action, are ideal candidates for pneumatic operation. Similarly, rotating axes can benefit from pneumatic rotary actuators, the most cost effective solution for pickup and drop-off rotational positions. |
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