How Does a Hard Drive Actuator Arm Work?

By Tiesha Whatley

The makeup of the items inside a hard drive is similar to the old record player. The hard drive is used to read and write data that is accessed by the computer. The actuator arm works hand in hand with the other moving parts of the hard drive to carry out its functions quickly and without failure. This is why the actuator arm is an essential part of the hard drive.

Makeup of the Hard Drive

The hard drive is made up of magnetic disks, spindles, heads, controllers, a motor and an actuator arm all encased in metal casing. The magnetic disks house the data used by computer programs. The heads and spindles are connected to the magnetic disks and spin the disks similar to spinning a record to retrieve the information (music). The actuator arm is connected to the motor. The controller controls all of the processes and collects the data as the actuator arm and the magnetic disks work together.

Makeup of the Actuator Arm

The actuator arm is part of the actuator assembly. To make up the whole head actuator, there are sliders, axles, coils, heads, the motor and two to three arms. The sliders are connected to the arms and attach them to the other parts of the actuator. On the tips of the actuator arms are the heads; they are used to pull off the data and write new data on the magnetic disk.

In the past, the actuator was connected to a stepping motor. The problem with stepping motors is that it needed the components to be in a parked position to read and write data. If there was a miscalculation in the timing of the movements, then the data would be corrupted. Also, stepping motors had a tendency to get very hot and cause mistakes in the registry of the data location. These days, linear motors are replacing the stepping motors. The linear motors are made up of voice coils that improve the integrity and accuracy of the actuator arm.

How It Works

To properly understand what the actuator arm does in the process of reading and writing data, you must understand how all of the parts of a hard drive work together to complete a common goal. When a request is made by the computer (to either read or write data), the controller receives this request and starts to check the registry. The controller looks for the data's location (to read data) or for an empty space on the magnetic disks (to write new data). Once the controller has located what it is looking for, the controller positions the magnetic disks in place for the actuator arm to do its job. The motor speeds up so that the actuator arm can move over the magnetic disk as they spin. The actuator arm is the component that actually pulls the data off the magnetic disks or writes new data to them.