High-DOF vs Low-DOF Robots
The most common robot configuration is one with six degrees of freedom (DOF), otherwise known as a six-axis robot. Industrial robots with six degrees of freedom have a full range of motion allowing them to automate most manufacturing applications. As the scope of robotics continues to expand so does the variability of robot degrees of freedom. Not every application benefits from having six degrees of freedom. Some may require more or less with either a high-DOF or low-DOF robot. Below is a look at the main differences between high-DOF and low-DOF robots.
AxesHigh-DOF robots are those with more than six axes. High-DOF robots can range from seven axes up to fifteen. Since high-DOF robots have more axes they have an enhanced range of motion. Seven-axis articulated robots are starting to gain traction in the robotic industry. These articulated robots feature an extra axis in their robotic manipulator arm which allows for better EOAT positioning. The extra axis also allows the robot to maneuver its arm around objects without affecting the end-effector, eliminating the need for a positioner. Other high-DOF robots include dual arm robots and robot transfer units or RTUs. Dual arm robots will be configured with a higher number of axes since they feature two robotic manipulators. RTUs are configured with a six-axis robot mounted to a track, making the track the additional axis.
Low-DOF robots are those with less than six axes. In manufacturing three-axis, four-axis, and five-axis robots are typically used for applications requiring less range of motion. Low-DOF robots may consist of articulated, delta, SCARA, or gantry robot types. Three-axis robots are able to rotate from the robot base, move the lower arm forward and backward, and lower and raise the upper arm. They are unable to control the movement of any EOAT device. Four-axis robots are capable of the same movements as three-axis robots with the ability to rotate the EOAT. Five-axis robots feature all of the above mentioned movements with the addition of pitch and yaw movements of the EOAT.
ApplicationsSince high-DOF robots feature an enhanced range of motion they are ideal for automating more complex applications. Most high-DOF robots are used for material handling processes such as automated assembly, packaging, part transfer, and machine tending. Seven-axis robots are now being used for welding automation. The Motoman VA1400 is a seven-axis welding robot. The additional axis allows for better torch positioning for incredibly accurate welding. Dual arm robots can complete different tasks simultaneously or use both of their arms to perform the same task for hyper productivity.
Low-DOF robots are best for simple, highly repetitive applications with straightforward movements due to their limited range of motion. Four-axis robots make some of the best palletizing robots. Most palletizing applications only require up and down motions which four-axis robots are capable of. The limited range of motion of four-axis robots provides the stability needed for heavy lifting applications. The FANUC M-410ic/185 is a four-axis palletizing robot.