Two machines with the same electric linear actuator can behave very differently: one stops cleanly at the end of travel, the other slams into a hard stop every cycle until the screw, gears or limit switch fail. The difference is how the stroke and limits are set. Stroke sets how far the actuator travels; limits set where and how it stops. Get both right and the motion stays repeatable.

1. Stroke, mounting distance and limits

Separate three terms first. Stroke is the straight-line travel from fully retracted to fully extended. Mounting distance is the centre-to-centre length when retracted. A limit is what stops the actuator before the end of travel. Choose stroke from the displacement the mechanism actually needs, then add a small margin. A margin that is too large lengthens the mounting distance and stresses the layout, so decide stroke first, then position the limits.

2. Built-in limits

Most electric linear actuators already contain mechanical limit switches, either microswitches or Hall sensors, that cut power at both ends of travel. They are set at the factory and usually need no adjustment. Built-in limits are simple to wire, compact and low cost, which suits stable loads and fixed end positions such as lift tables, gates and flap mechanisms. Remember that built-in limits protect the actuator itself; they are not a substitute for a machine stop. Forcing the internal switch to absorb impact every cycle shortens its life.

3. External limits

External limits are added by the machine builder: a hard stop, a travel switch or a proximity sensor. As the actuator moves, the mechanism trips the switch first, then the controller cuts power to the actuator. This suits strokes that must be adjusted on site, positions that need high accuracy, or several mechanisms that must move together. Models with an encoder or potentiometer can provide position feedback for a soft limit: the controller remembers the target position and stops there with no extra mechanical switch. External limits take more wiring and setup, but they protect the actuator far better.

4. Setting stroke and limits in the right order

Work in this order and do not reverse it. Size the stroke to the mechanism and leave a small margin at both ends. Push the mechanism by hand to each end and check for interference or dead points. Let the machine stop or sensor trip first, then let it stop the actuator. Cycle several times and confirm the stop position is repeatable. Finally check that the actuator still has stroke margin against its internal limits so it never stalls hard.

5. Common problems and protection

Three problems come up often. Stop position drifting usually means a loose stop or a shifted switch: refit and re-test. Current still flowing at the end of travel means the limit does not truly cut power, which heats the motor: check the wiring and control logic. Knocking after the mechanism has arrived means the limit order is reversed; the machine must stop before the actuator. For protection, also consider over-current and self-locking options. A self-locking unit holds position when power is removed, and stall protection stops the actuator when the mechanism jams, limiting damage.

6. Conclusion

Stroke and limits are two sides of one setting: stroke decides how far the mechanism goes, limits decide where it stops safely. Built-in limits are convenient and external limits are flexible; used together they are the most reliable. Let the machine stop first and the actuator stop second, and the unit will last far longer.