How linear actuators work

Linear actuator technology consists of a stepping motor in which the shaft is replaced by a screw. The centre part of the rotor is tapped to convert it to a 'nut' adjusted to that screw. By preventing the screw turning (anti-rotation), it can move axially, to give the linear motion required.
 
The increment, that is the linear progression corresponding to each step of the motor, is given by the screw pitch divided by the number of motor steps.
 
This is selected to suit the actuator characteristics required. The longer the pitch, the quicker the advance but the lower the power of the device. Conversely, a fine pitch limits the speed but increases the power available.

1 Screw 2 Bearing 3 Ball Bearing 4 Front bent plate 5 Casting 6 Nut 7 Rear bent plate 8 Mounting plate 9 Rotor 10 Coil 11 Coil