I. Definition and Classification of Robots: According to ISO 8373, a robot is defined as an industrial automation device whose position can be fixed or movable, capable of automatic control, reprogrammable, multifunctional, and whose end effector position is programmable in three or more degrees of freedom. Here, degrees of freedom refer to the axes that can move or rotate. Industrial robots are mainly classified according to their structural form and programming coordinate system into articulated robots, mobile robots, underwater robots, and Cartesian coordinate robots. They are also classified according to their main functional characteristics and applications into mobile robots, underwater robots, cleanroom robots, Cartesian coordinate robots, welding robots, surgical robots, and military robots. Cartesian coordinate robots, widely used in various industries, primarily use linear motion axes. Each motion axis typically corresponds to the X-axis, Y-axis, and Z-axis in a Cartesian coordinate system. Generally, the X and Y axes are horizontal motion axes, and the Z-axis is the vertical motion axis. In some applications, the Z-axis includes a rotational axis, or a swing axis and a rotational axis. In most cases, the angles between the linear motion axes of a Cartesian coordinate robot are right angles. 2. Main Components of a Cartesian Robot A typical 3D Cartesian robot consists of X-axis, Y-axis, Z-axis, and drive motors. In addition, a complete robot system also requires a control system and a gripper, which are described below: 2.1 Linear Motion Axis: Also called a linear motion unit, it is an independent motion axis, mainly composed of aluminum or steel profiles supporting the carrier, linear guides installed inside the profiles, a motion slider, and a synchronous belt that drives the slider to move at high speed. 2.2 Drive System of the Motion Axis The transmission of a Cartesian robot is mainly achieved by the rotation of the drive motor driving the synchronous belt, which in turn drives the slider on the linear guide. When the maximum speed of the drive axis is below 600 rpm, a stepper motor is usually selected; otherwise, an AC servo motor is used. 2.3 Control System of a Cartesian Robot The robot needs to complete specific tasks within a certain time, such as completing a handling operation every 10 seconds. While performing tasks such as gripping, acceleration, high-speed movement, deceleration, and workpiece release, it also needs to achieve timing coordination and synchronization with related equipment through communication or I/O ports. In addition, in adhesive application, each motion axis needs to complete linear and circular interpolation movements. Therefore, the number of control axes, I/O ports, and software functions of the CNC system must be selected according to the specific application requirements. Typically, a CNC system, PLC, industrial computer with motion control card and drive motor with axis card function and I/O ports is used as the control system. 2.4 End effector of Cartesian robots—the gripper system: Depending on the specific application, the gripper system may be a pneumatic suction cup, pneumatic gripper, electric gripper, electromagnetic suction gripper, welding gun, glue gun, special tools, and testing instruments, etc. In many cases, it can grasp multiple workpieces at once. The main structural forms and characteristics of 3D Cartesian robots: Typical 3D gantry Cartesian robots can be easily and quickly combined into various forms of Cartesian robots with different dimensions, strokes, and load capacities, such as wall-mounted, cantilevered, gantry, or inverted types. There are hundreds of successful application cases of structural forms, from simple two-dimensional robots to complex five-dimensional robots. In automated production lines across various industries, from motors to automobiles, numerous Cartesian robots and other equipment work in strict, synchronized coordination. It can be said that Cartesian robots can handle almost all industrial automation tasks. Here are their main features: 3.1 Arbitrary Combinations into Various Styles: Each linear motion axis is up to 6 meters long, with a load capacity ranging from 10 kg to 200 kg. Nearly a hundred different Cartesian robot structures exist in practical applications, and these structures can be arbitrarily combined into new configurations. 3.2 Ultra-Large Stroke: Because a single gantry-type linear motion unit is 6 meters long, and multiple units can be easily cascaded to create ultra-large strokes, their working space is virtually unlimited, ranging from small mobile phone dispensing machines to large cutting machines with an 18-meter stroke, milling machines with an 8-meter stroke, and inspection robots measuring 6m x 6m x 3m. For ultra-large strokes, linear guides and rack and pinion drives are used. 3.3 Strong Load Capacity: The load of a single linear motion unit is typically less than 200 kg. However, when using a rigid connection of dual or multiple sliders, the load capacity can increase by 5 to 10 times. When two or four linear motion units are connected side by side, the load capacity can increase by 2 to 4 times. When using a multi-slider structure, the load capacity can increase to several tons. 3.4 High dynamic characteristics: Under light loads, its maximum operating speed can reach 8 meters per second, and its acceleration can reach 4 meters per second. This gives it very high dynamic characteristics and very high work efficiency, typically completing a work cycle in a few seconds. 3.5 High precision: Depending on the transmission method and configuration, its repeatability throughout the entire stroke can reach 0.05mm to 0.01mm. 3.6 Strong expandability: The structure can be easily changed or programmed to suit new applications. 3.7 Simple and economical: Compared with articulated robots, Cartesian robots are not only more intuitive in appearance but also have lower construction costs. Programming is simple, similar to CNC milling machines, and it is easy to train employees and maintain them, making them very economical. 3.8 Capable of Complex Tasks: Employing a five-axis or higher CNC system with RTCP functionality, it can complete highly complex tasks such as spraying, shot peening, inspection, and machining. 3.9 Long Lifespan: Maintenance of Cartesian robots typically involves periodic lubrication, with a lifespan generally exceeding 10 years, and up to 20 years with proper maintenance. 3.10 Wide Application Range: It can easily assemble various types and sizes of grippers, capable of handling many common tasks such as welding, cutting, handling, loading and unloading, packaging, palletizing, depalletizing, inspection, flaw detection, sorting, assembly, labeling, coding, and spraying. IV. Selection and Maintenance of Cartesian Robots 4.1 Selection: First, the robot's external structure should be selected based on the load size, stroke, work cycle, and workspace limitations. After selecting the structural form, the form and model of each axis should be chosen based on the stroke and deformation. For heavy loads and high impact conditions, a composite motion axis consisting of two or four motion axes can be selected. The assembly between the various motion axes is also crucial. Not only must their perpendicularity be ensured, but sufficient resistance to impact and deformation in all directions must also be considered. Since the robot needs to complete a motion cycle within seconds, the selected drive motor must have sufficient driving force, typically 100% higher than the theoretical calculation value. When the ratio of the load's moment of inertia to the drive motor's moment of inertia is greater than 12, a precision planetary gearbox from Neukärcher (Germany) should be selected. For ultra-high dynamic and positioning accuracy requirements, linear motors can be used. However, linear motors are difficult to install and protect, generate a lot of heat, pose a high risk of impact, are difficult to control, and are expensive, so their use should be cautious. The difficulty in protecting them and the high heat generation remain global challenges in the machine tool industry. 4.2 Installation Robots generate strong impact forces during acceleration and deceleration, and typically operate 24 hours a day, so the robot must be securely mounted on a support. The robot's support must have sufficient impact resistance and feet to ensure no shaking under long-term high-speed, high-dynamic motion impacts. Furthermore, the parallelism, flatness, and perpendicularity between the motion axes must be ensured during installation. 4.3 Maintenance Typically, each motion axis of the robot requires periodic lubrication of the linear guide rail through the lubrication hole of the slider after a certain distance of movement. The lubrication cycle varies depending on the robot's operating environment and speed. In industries such as food and glass cutting, motion axes with dustproof belts should be selected, and the lubrication cycle should be shortened. In situations involving water spraying, the lubrication cycle should also be shortened. V. Applications and Prospects Cartesian robots, with their unique advantages, are widely used in Western countries to perform a range of tasks including welding, handling, loading and unloading, packaging, palletizing, depalletizing, inspection, flaw detection, sorting, assembly, labeling, coding, gluing, and cutting. They are highly praised by industries such as packaging machinery, printing machinery, automotive, food production, pharmaceutical production, electronics, machinery manufacturing, and cosmetics production. With increasing automation, environmental protection requirements, hygiene regulations, production efficiency, and labor costs, Cartesian robots will inevitably be widely adopted by various industries in China as well.