Robot Range of Motion

FANUC R2000ib 125L R30ia Motoman MA1400 FANUC M710ic 50 Motoman HP6 NX100 FANUC Arcmate 120ic
An industrial robot’s range of motion determines the movements it is capable of. Range of motion for a robot depends upon the degrees of freedom (DOF) it has. Each degree of freedom is represented by an axis. Each axis contains a motor that is responsible for producing a specific motion.

Most industrial robots have between three to six axes. Robots with fewer than six axes are considered to be low-DOF robots and therefore will have less range of motion than a six-axis robot. There are also articulated robots with greater than six axes and these are considered high-DOF robots. However, six-axis robots remain the most popular as they provide a full range of motion which allows them to access a unit of space from any angle. The range of motion of six-axis robots is most similar to that of the human arm, which is why they are able to automate a variety of manufacturing processes. The range of motion of six-axis robots allows them to operate on the x, y, and z planes as well as shift and rotate. The range of motion of each axis is defined as the following:

  • • Axis 1 - Axis one allows the robotic manipulator arm to move 180 degrees from its center from left to right and vice versa for linear movements.

  • • Axis 2 - Axis two controls forward and backwards motions of the robotic arm on the x and y planes. The FANUC R-2000ic is able to lift objects up and down because of the second axis.

  • • Axis 3 - Axis three allows for the raising and lowering of the robotic arm, similar to axis 2, but on all three (x, y, and Z) planes.

  • • Axis 4 - Axis four allows for the rotation of the robot wrist and EOAT.

  • • Axis 5 - Axis five controls the pitch and yaw movements of the end-effector. With axis five robots can move their EOAT up and down or left and right.

  • • Axis 6 - Axis six provides robots with the ability to change a part’s orientation a full 360 degrees. The sixth axis provides complete rotation of the robot’s wrist.

A robot’s range of motion is important as it determines the types and complexity of applications it can automate. More complex applications will require a greater range of motion. If parts need to be repositioned, a six-axis robot will be needed. The full range of motion of six-axis robots is one of the main reasons they are popular for robotic automation, as they can perform most applications.

Not every application will benefit or need a full range of motion. Those automating simpler processes can use a robot with less range of motion. Robots with fewer axes can be more affordable, easier to operate, and in some cases faster. A simple pick and place application that does not require part orientations to be changed can be automated by a three-axis robot. Automated palletizing applications are actually best for four or five-axis robots. Having a more limited range of motion provides greater stability for lifting heavy loads and part repositioning is often not required. The Motoman MPL160 is a four-axis robot designed specifically for palletizing. When selecting an industrial robot, it is important to consider the number of axes as this will determine the robot’s range of motion.

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