AiVibeCNC Axis Nomenclature (X, Y, Z, A, B, C)
CNC axis nomenclature is the convention, defined in ISO 841, for naming machine motions: linear axes X, Y and Z in a right-handed coordinate system, and rotary axes A, B and C turning about X, Y and Z.
ISO 841 defines a right-handed Cartesian coordinate system for numerically controlled machines. The Z axis is parallel to the principal spindle, and its positive direction moves the tool away from the workpiece. The X axis is normally horizontal and parallel to the work-holding surface, and Y completes the right-handed system. Rotary axes A, B and C rotate about X, Y and Z, with positive direction given by the right-hand screw rule, and secondary linear axes U, V and W run parallel to X, Y and Z.
The convention lets programmers, CAM software and machine builders describe motion consistently. Machines are described by their axis count, such as 3-axis vertical mills, 4-axis machines with a rotary table, and 5-axis machines with two rotary axes. On a typical lathe, Z runs along the spindle centreline and X is radial, often programmed as a diameter.
Motion is defined as the tool moving relative to the workpiece, even when the machine actually moves the table, which can confuse new operators. Builders may add axes, such as sub-spindles or tailstocks, and name them according to their own documentation. The machine manual and the CAM machine definition must agree on axis names, directions and limits before programs are run.
Key points
- ISO 841 defines the right-handed coordinate system for NC machines
- Z is parallel to the main spindle and positive Z moves the tool away from the work
- A, B and C are rotary axes about X, Y and Z respectively
- Motion is described as the tool moving relative to the workpiece
Where AiVibe comes in
AiVibe designs and manufactures the AiAmbA AI Factory: edge devices plus AI agents that let people talk to CNC, PLC and robot controllers in plain language. Agents only propose changes, and a trained operator confirms each one.