CNC milling operates by having a computer program, typically derived from a CAD design, direct the motion of cutting tools along several axes, generally three or more. This enables the attainment of the intended shape and dimensions. The cutting tools employed can be end mills, drills, and other specialized implements, which subtractively remove material. As a result, the workpiece is incrementally shaped into the desired configuration.
CNC milling provides a high degree of precision, reproducibility, and adaptability. It is thus appropriate for manufacturing components featuring complex geometries, strict tolerances, and excellent surface finishes. This technology is extensively utilized in various industries like manufacturing, aerospace, automotive, electronics, and others. Its applications span from prototypes and single-piece parts to large-scale production batches.

For parts with basic designs intended for general applications, extremely precise measurements or an ultrasmooth surface finish may not be crucial. Nevertheless, when dealing with intricate designs, more accurate milling operations are typically required. Milling machines are classified based on the number of axes they possess, commonly available in 3-axis, 4-axis, or 5-axis configurations.
Three-axis milling machines are widely used. They are capable of performing cutting operations along the vertical (Z-axis) and horizontal (X and Y axes) directions. Despite their versatility, these machines face limitations when it comes to creating specific geometries, such as undercuts, which often necessitate a more specialized type of milling equipment.
Five-axis milling machines offer the highest level of functionality, incorporating rotational movements along both the X and Y axes. These machines are the most comprehensive in the milling machine family and are predominantly employed for manufacturing highly complex components. Applications include the production of medical devices and implants in the medical field, as well as impellers and aerospace structures, where intricate geometries and tight tolerances are of utmost importance.