Each actuator usually causes rotary or linear motion along an axis. The number of axes is normally the same as the number of degrees of freedom of the robot. Motions of actuators in the end effector, such as closing grippers or the motion of a drill, do not constitute additional degrees of freedom. Depending on the robot's geometry, motion of one or more axes may be required for the robot to move to a new location in space. There are usually three axes used to move the robot's wrist-end effector interface to a position in space.
Additional axes provide for rotation at that point to permit flexibility in orientation.
One, two, or three rotating axes at the wrist may be used, depending on the needs of the application or the robotic system sophistication. Six degrees of freedom are commonly available with articulated arm and gantry robots. Seven or more axes are used for some special applications. An example is an articulated arm-welding robot required to work on the far side of an auto body.