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Actuator stroke 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. The actuators are capable of fixed stroke values or can be adjusted to produce ranges of motion suitable for the particular application. Stroke values for linear and rotary actuators are determined and expressed in different ways, with 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 working motion output is known as its stroke. A thorough understanding of the ideal, minimum and maximum actuator stroke values for any application is critical for 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, actuated 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 where exact matches are possible between the actuator output and the secondary device actuation requirements. Other types of actuators feature integral tuning controls that allow the device output to be set according to application requirements. In some cases, the actuator power supply may also be routed through travel limits that stop the actuator when it reaches the optimal stroke length.
Measuring the stroke of an actuator can be tricky, especially in the case of rotating devices. Fixed output linear actuators are the easiest examples to measure. For this, the actuator is disconnected from the secondary device and its mechanism is placed in the neutral or null position. The entire length of the actuator is then measured from its rear surface to the center of the actuator arm link pin. The device is then triggered to produce its full motion and measured again, the difference between the two measurements being the actuator stroke value.
The actuator stroke of a rotary actuator is a little more difficult to establish. Devices that develop less than one full turn of the output movement have travel values expressed in degrees. There are several ways to establish 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 output is expressed according to the number of complete revolutions they produce.