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How spindles (lead screws) work in an electric linear actuator

Curious about the most important features of a spindle in an electric actuator? Learn how this essential component is directly related to the efficiency of modern linear lead screw actuators, and how spindle quality, spindle pitch, and stroke length affect the performance and service life.

Find out how the spindle (also called a ‘lead screw’) pitch is connected to an actuator’s efficiency and self-locking ability, and why an actuator will always provide the same efficiency output, regardless of the load applied. Our man Hunter Stephenson explains the essentials in this video.

A high-quality spindle is the essence of achieving an optimal actuator performance. The iron bars used for LINAK spindles are carefully selected before rolling the spindle threads.

Which spindle type and spindle nut to select depends on the load and performance requirements of the actuator. For example, a long spindle nut is better for lifting heavier loads. To obtain a long and reliable service life for actuators with high spindle pitches, more tracks are added to efficiently distribute the forces from the industrial application to the spindle and the nut.

The core diameter of the actuator spindle (not including the tracks) determines the strength of the spindle, thus the actuator.

A spindle pitch is the linear distance a nut travels, rotating once (360 degrees) around a spindle. A high spindle pitch entails a higher actuator efficiency as there is less friction between the nut and the spindle. But, a high spindle pitch also means a lower self-locking ability. Self-locking means that the actuator does not backdrive while stopped at a target position. Linear spindle actuators that are not self-locking require a brake in order to keep them in a fixed position.

Because of the spindle and its shape, an electric actuator will always provide the same efficiency output, regardless of the load applied. Also, regardless of the load, speed will not vary between push and pull movement. When selecting an actuator, a rule of thumb is to multiply the load by the speed to calculate the power needed for the right movement solution.

When considering actuators with long stroke lengths in push, the maximum load specification is typically reduced to decrease the strain on the actuator.

Finally, actuators operating machinery with high safety requirements often have a safety nut added. This ensures that the actuator travels slowly inwards in case the spindle nut is worn down.

If you have questions about spindles for industrial electric linear actuators, please feel free to contact your local LINAK office.


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