How many applications for Rotary Actuators can you name?
Most engineers can name a few of them like diverter conveyors, turn over tables, or actuation for a ball valve. These are some of the simple ones. Many machine automation specialists are now using them for clamping, pick and place, or indexing too.
Have you ever heard of an indexing rotary actuator?
Indexing is a unique application that I thought I would discuss a little more because it is unique and not well known. Many applications that need indexing engineers might use a stepper or servo drive motor to stop at a discrete angle in a process. If those positions are fixed and are never variable then an indexing rotary actuator maybe what you need. These nifty devices are just a specialized rotary actuator with a one-way clutch a cam and a clutch.
I found this illustration below on the Rotomation website (https://www.rotomation.com/index.php/literature/tech-guides/indexer-operation).
The drawings on the left show how the clutch, ratchet, and gear work together to ensure one-way rotary indexing.
Indexing rotary actuators can be built for virtually any indexing angle, but 45, 90 and 180 are the most popular, but they can be designed for any angle from 12 to 360 degrees. The indexing actuators are easy to use with a standard 4 way pneumatic valve to drive the piston in one direction and reset the actuator in the reverse. With standard air pressure of up to 150 psi you can be sure that the torque they deliver keeps the actuator in place because the air pressure driving the piston locks against the gear and with less than 0.2 degrees of backlash we can assure a positive position with the accuracy of a low-cost servo motor.
So now that you know how indexing actuators work you may think more about using them in applications like walking beam or indexing conveyors, index tables or star wheels. Sizing them is basically the same as a standard rotary actuator. You just need the total torque that is needed to produce your motion and then consider the bearing load that the shaft will take axially and finally determine the maximum impact energy of the load in motion.
I hope that this pneumatic indexing 101 blog was valuable to you and you might be more tempted to use a cost-effective indexing rotary actuator next time you need simple movements of a rotary device.