The number of axes, or degrees of freedom (DOF), determines a robot's flexibility and dexterity. Each axis is a joint that provides an additional degree of freedom.

Major Axes (Axes 1-3)

These are the first three joints, starting from the base. Their primary function is to position the robot's wrist assembly within the work envelope. They are the main determinants of the robot's reach and overall workspace shape. For example, a 3-axis Cartesian robot can position its end-effector anywhere within its rectangular workspace, but it cannot change the tool's orientation.

Minor Axes (Axes 4-6)

These are the wrist joints. Their function is to orient the end-effector. To achieve any arbitrary orientation in 3D space (e.g., pitch, yaw, and roll), a three-axis wrist is required. A 6-axis robot (3 major + 3 minor axes) is the standard for general-purpose applications because its 6 DOF perfectly match the 6 DOF of an unconstrained rigid body in space (3 for position, 3 for orientation). This allows it to place its end-effector in any position and orientation within its dexterous workspace, which is essential for complex tasks like welding a curved seam or assembling parts at odd angles.

Redundant Axes (Axes 7+)

A robot with more than six axes is considered redundant. This extra flexibility does not increase the robot's ability to reach a point with a given orientation, but it provides multiple arm configurations to achieve the same end-effector pose. This is extremely useful for maneuvering around obstacles in a cluttered environment or avoiding singular configurations (positions where the robot loses one or more degrees of freedom and its dexterity is compromised).