Low Degree of Freedom Robots
The degrees of freedom (DOF) of an industrial robot determine the movements a robot is capable of. Each degree of freedom is represented by a robotic axis. A six-axis robot is considered the standard for robotic automation as it has six degrees of freedom for a full range of motion that is most similar to the range of motion of the human arm. This is why six-axis robots like the FANUC Arcmate 120ic or Motoman HP20D are so common in manufacturing. Not every manufacturing application requires or benefits from a six-axis robot. There are some in which an articulated robot with fewer degrees of freedom is best, this is where low-DOF robots come in.
Low-DOF robots are those with fewer than six degrees of freedom, meaning they have less than six axes. For industrial manufacturing low-DOF robots typically include three-axis, four-axis, and five-axis configurations.
Three-axis robots are some of the simplest to operate. Gantry, delta, and SCARA robot structures may be configured with three axes. These robots are able to move along three planes, the x, y, and z planes. They are able to rotate from the robotic base, extend the lower arm both forwards and backwards, and lower and raise the upper portion of the robotic arm. Since three-axis robots feature a limited range of motion they are best for automating simple applications that are highly repetitive. Robotic pick and place applications are the most common for three-axis robot automation. The three-axis FANUC M-2ia is ideal for simple pick and place applications. Those looking to automate uncomplicated manufacturing processes could benefit from a three-axis robot as they are easy to maintain and typically less than the cost of a six-axis robot.
Four-axis robots are able to complete the same movements as three-axis robots with the additional ability to rotate the robot end-effector due to the fourth axis in the robot wrist. Four-axis robots have a little bit more range of motion with the ability to change the orientation of workpieces. SCARA, delta, and articulated robot types can be configured with four degrees of freedom. Four-axis robots may automate assembly, machine tending, and light palletizing applications if consisting of either SCARA or delta structures. Four-axis articulated robots are common for palletizing automation. The limited range of motion provides the extra stability needed for the heavy lifting often required by palletizing applications. Palletizing typically only requires straightforward up and down movements which is ideal for the four-axis FANUC M-410ic/185.
Five-axis robots have one less degree of freedom than six-axis robots, putting them in the low-DOF category. Five-axis robots are capable of additional tooling movements than four-axis robots with a fifth axis located in the upper arm. These robots can move their tooling in pitch motions (moving the front or back of the EOAT upward) and yaw motions (moving the EOAT side to side). Five-axis robots are common for palletizing applications. The FANUC M-710ic/50H is a five-axis palletizing robot. Since these robots have more range of motion than other low-DOF robots they can also automate material handling and pick and place processes.
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