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Actuator travel is a quantitative term used to express the full range of working motion that any actuator is capable of. This operating variable is a critical consideration when choosing actuators or designing systems based on existing drives. Actuators are capable of fixed travel values or can be adjusted to produce suitable ranges of motion for the particular application. Stroke values for linear and rotary actuators are determined and expressed in different ways, with the linear types generally being easier to measure. Some multi-turn rotary actuators do not have stroke values as such, but are defined by the number of full revolutions they produce.
The full extent of an actuator’s work motion output is known as the stroke. A thorough understanding of the ideal, minimum, and maximum actuator travel values for any application is critical to the safe and efficient operation of the actuator and the mechanism to which it is connected. If an incorrectly rated actuator is used, a loss of efficiency is usually the best case scenario. At the other end of the scale, destruction of the actuator, the driven mechanism, or serious injury to the operator is a distinct possibility if the actuator stroke is not suitable for the specific application.
Fixed-stroke actuators produce a finite, predefined range of motion. These devices are used when an exact match between the actuator output and the actuation requirements of the secondary device is possible. Other types of actuators have integral tuning controls that allow the output of the device to be configured according to the requirements of the application. In some cases, the actuator power supply can also be routed through travel limits that stop the actuator when it reaches the optimum travel length.
Measuring the travel of an actuator can be tricky, especially for rotary devices. Fixed output linear actuators are the easiest examples to measure. To do this, the actuator is disconnected from the secondary device and its mechanism is placed in the neutral or null position. The overall length of the actuator is then measured from its back surface to the center of the actuator arm connecting pin. The device is then activated to produce its full movement and is measured again, the difference between the two measurements being the value of the actuator stroke.
The actuator travel of a rotary actuator is a bit more difficult to set. Devices that develop less than one full turn of the output motion have travel values expressed in degrees. There are several ways to set this value if it is unknown, one of which is to use a specially designed protractor template. For obvious reasons, multi-turn rotary actuators are not classified according to stroke length. Their performance is expressed by the number of complete revolutions they produce.