In today’s industrial automation field, robots handle difficult, dangerous, and repeated tasks. These jobs include the lifting of heavy objects, pick and placing of parts, assembly of components, or assisting manual labor in sorting products. Robots can be grouped into several categories depending on their movement, degrees of freedom, axes of rotation, and function.
Stationary robots are those that perform their task without changing positions. The term “stationary” is more associated with the base of the robot and not the whole robot. The robot moves above the base to perform the desired operation. These robots manipulate their environment by controlling the position and orientation of an end-effector. End-effectors could be a drilling, welding, or gripper device.
Stationary robots break down into different groups:
Cartesian, or gantry, robots (also known as rectilinear robots) have three linear joints that use the Cartesian coordinate system. They operate within the x-, y-, and z-axis by using linear guide rails. These guide rails help translate the end-effector into the correct position by moving the each linear guide rail in the corresponding axis. These robots are typically used for pick-and-place work, application of sealant, assembly operations, or handling machine tools and arc welding.
A cylindrical robot has at least one rotary joint at the base and at least one prismatic joint to connect the links. Along the joint axis, the rotary joint uses a rotational motion; along the prismatic joint, it moves in a linear motion. Their movements occur within a cylindrical-shaped work envelope. Cylindrical robots are used for assembly operations, handling of machine tools and die-cast machines, and spot welding.
These are also known as polar robots. The arm is connected to the base with a twisting joint, and has a combination of two rotary joints and one linear joint. The axes of the combined joints form a polar coordinate system and operate within a spherical-shaped work envelope. These robots are used for handling of machine tools, spot welding, die casting, fettling machines, and gas and arc welding.
SCARA robots are primarily used for assembly applications. The compliant arm, which is cylindrical in design, is comprised of two parallel joints that provide it with compliance in one selected plane. These robots are used for pick-and-place work, application of sealant, assembly operations, and handling of machine tools.
Robotic arms, or articulated robots, feature rotary joints that can range from a simple two-joint structure to a complicated structure with 10 or more joints. The arm is connected to a base that has a twisting joint. Rotary joints connect the links in the arm; each joint is a different axis and provides an additional degree of freedom. Industrial robotic arms have four or six axes. Such robots are primarily used for assembly operations, die-casting, fettling machines, gas and arc welding, and applying paint.
Parallel robots are also known as delta robots. They are built from jointed parallelograms connected to a common base. The parallelograms move a single end of arm tooling in a dome-shaped envelope. They are used primarily in the food, pharmaceutical, and electronic industries. The robot itself is capable of precise movement, making it ideal for pick-and-place operations.