A Cartesian coordinate robot (also called linear robot) is an industrial robot whose three principal axes of control are linear (i.e. they move in a straight line rather than rotate) and are at

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s to each other. The three sliding joints correspond to moving the wrist up-down, in-out, back-forth. Among other advantages, this mechanical arrangement simplifies the robot control arm solution. It has high reliability and precision when operating in three-dimensional space. As a robot coordinate system, it is also effective for horizontal travel and for stacking bins.

Configurations

Robots have mechanisms consisting of rigid links connected together by joints with either linear (prismatic ''P'') or rotary (revolute ''R'') motion, or combinations of the two. Active prismatic ''P'' and active revolute ''R'' joints are driven by motors under programmable control to manipulate objects to perform complex automated tasks. The linear motion of active prismatic ''P'' joints may be driven by rotary motors through gears or pulleys. Cartesian coordinate robots are controlled by mutually perpendicular active prismatic ''P'' joints that are aligned with the ''X, Y, Z'' axes of a

Cartesian coordinate system A Cartesian coordinate system (, ) in a plane is a coordinate system that specifies each point uniquely by a pair of numerical coordinates, which are the signed distances to the point from two fixed perpendicular oriented lines, measured in t ...

. Although not strictly ‘robots’, other types of manipulators, such as computer

numerically controlled Numerical control (also computer numerical control, and commonly called CNC) is the automated control of machining tools (such as drills, lathes, mills, grinders, routers and 3D printers) by means of a computer. A CNC machine processes a piec ...

(CNC) machines,

3D printers 3D printing or additive manufacturing is the construction of a three-dimensional object from a CAD model or a digital 3D model. It can be done in a variety of processes in which material is deposited, joined or solidified under computer co ...

or pen plotters, also have the same mechanical arrangement of mutually perpendicular active prismatic ''P'' joints.

Joint topology

A single chain of links and joints connects a moving object to a base of serial manipulators. Multiple chains (limbs) connect the moving object to the base of

parallel manipulator A parallel manipulator is a mechanical system that uses several computer-controlled serial chains to support a single platform, or end-effector. Perhaps, the best known parallel manipulator is formed from six linear actuators that support a mova ...

s. Most Cartesian coordinate robots are fully serial or a combination of serial and parallel connected linkages. However, there are some Cartesian coordinate robots that are fully parallel-connected.

Degrees of freedom

Since they are driven by linear active prismatic ''P'' joints, Cartesian coordinate robots typically manipulate objects with only linear translation ''T''

degrees of freedom Degrees of freedom (often abbreviated df or DOF) refers to the number of independent variables or parameters of a thermodynamic system. In various scientific fields, the word "freedom" is used to describe the limits to which physical movement or ...

. However, some Cartesian coordinate robots also have rotational ''R'' degrees of freedom.

Construction

Each axis of a Cartesian coordinate robot typically is a linear stage consisting of a linear

actuator An actuator is a component of a machine that is responsible for moving and controlling a mechanism or system, for example by opening a valve. In simple terms, it is a "mover". An actuator requires a control device (controlled by control signal) a ...

geometrically parallel with linear bearings. The linear actuator is typically between two linear bearings spaced apart from each other to support

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loads. Two perpendicular linear stages stacked on top of each other form an XY table. Examples of XY tables include the XY axes of milling machines or precision positioning stages. At least one of the linear stages of cantilevered Cartesian coordinate robots is supported at only one end. Cantilevered construction provides accessibility to parts for pick-and-place applications such as laboratory automation for example. Cartesian coordinate robots with the horizontal member supported at both ends are sometimes called gantry robots; mechanically, they resemble gantry cranes, although the latter are not generally robots. Gantry robots are often quite large and may support heavy loads.

Applications

Popular applications for Cartesian coordinate robots are computer numerical control machine ( CNC machine) and

3D printing 3D printing or additive manufacturing is the Manufacturing, construction of a three-dimensional object from a computer-aided design, CAD model or a digital 3D modeling, 3D model. It can be done in a variety of processes in which material is ...

. The simplest application is used in milling machines and

plotter A plotter is a machine that produces vector graphics drawings. Plotters draw lines on paper using a pen, or in some applications, use a knife to cut a material like vinyl or leather. In the latter case, they are sometimes known as a cutting pl ...

s where a tool such as a router or pen translates across an ''X-Y'' plane and is raised and lowered onto a surface to create a precise design. Pick and place machines are another application for Cartesian coordinate robots. For example, overhead gantry Cartesian robots ar
applied
for continuous parts loading and unloading on CNC lathes production lines, performing 3-axis ''(X, Y, Z)'' pick and place operations of heavy loads with high speed performance and high positioning accuracy. In general, overhead gantry Cartesian robots are suitable for many automation systems.

References