How does a linear actuator work?

Nearly every single electric motor transforms electrical energy into rotational motion, allowing them to spin connected objects. But turning this motion into a linear one requires extra parts that all assemble into a single unit referred to as a linear actuator. As the name implies, this device can push or pull in a single axis whenever a charge is applied and reverse direction when the polarity of the charge is reversed. YouTuber Michael Rechtin wanted to build one for much cheaper than could otherwise be found online and with readily available off-the-shelf parts.

Rechtin started his project by first disassembling a purchased linear actuator and seeing how it works internally. The base of the housing contains a brushed DC motor, which is attached to a series of reduction gears that take the high-speed, low-torque rotation from the motor and transform it into low-speed, high-torque rotation. The final gear is connected to a linear rod that moves a threaded insert up or down depending on its direction. And finally, a pair of switches cut power to the motor when a limit has been reached.

Designing a custom one

With this knowledge in mind, he set to work designing an initial version of his own linear actuator. In keeping with the original, Rechtin chose a single 24V brushed DC motor that turns a pair of reduction gears. To further save on costs, he opted to use a bolt paired with a hex nut rather than the more expensive ball screw configuration. Finally, everything was encased in a custom housing that could be easily 3D-printed and assembled.

The next revisions

Although the first version worked, it did lack a few key features. Namely, there was no point in the rear for a pivot point, and the absence of any limit switches meant that the actuator’s shaft would either fall out the end or get jammed based on its direction. To solve these problems, Rechtin added a pair of limit switches along with a single diode that spans the terminals of both and only let current pass through when the correct one is closed and the other is open. He also modified the enclosure to hide the ugly wires below and swapped out the weaker FDM gears for more durable, resin-based cogs.

Test results

After completing the project, Rechtin wanted to know just how strong his design was compared to the original store-bought device. Much to his delight, it successfully crushed a soda can and was then able to apply over 100kg of force to a load cell. For more information about how Rechtin created this DIY linear actuator, you can watch his video here on YouTube.