People have been trying to establish a good method for linear motion for millennia, ever since they started using tree trunks as a rolling element, but common applications in precision machinery only happened about 100 years ago. It's very difficult to move a large static object with friction force because of its weight and inertia. Thus ancient engineers developed the idea of putting large blocks of stone, for instance, onto a constantly moving sequence of rolling logs. Linear guides are part of the modern mechanism for doing this. They work by creating a kind of perpetual stroke motion using steel ball bearings, which theoretically enable an unending stroke action. They are used for machine tools such as lathes, robotic processes and high precision manufacturing such as semiconductors.
In an electric linear guide system, an electric motor is used to provide the initial momentum and maintain the drive process at a predetermined speed, via a screw thread assembly. The amount of torque and thrust required for the load determines the power output of the motor. The linear guide moves by means of the steel balls rolling in a grove along a rail in the assembly, topped by a ball slide. When these balls reach the end cap, they are forced by a return guide to change direction. This guide sends the balls into a circulating hole inside the ball slide, where they continue their journey back to the other end of the circuit.