Is zero-based indexing impossible?

What is an Indexing rotary actuator (pneumatic)?

• I need to rotate a table at 90 degree intervals (with significant time between intervals). I saw indexing rotary actuators and thought they fit the bill. The system I have now (still in design phase) is a standard 90 degree actuator with a ratcheting system so that when the actuator returns to the non-rotated position it won't turn the table back. How can I replace this? Is an Indexing Rotary Actuator what I need, or is there something else? Other information: Not a high speed requirement No water/oil/corrosive substances Source is 120psi, high flow

• Answer:

  I can't understand what is wrong with the one you have at the moment. It seems to fulfill your requirements. Could you not arrange it so that the next time it operates, it will turn the table another 90 degrees? Maybe you could use a link, similar to a con-rod in a car, connected to another link which is fixed to the table centre shaft. What about an electric motor??