What are 3-axis, 4-axis and 5-axis machining in CNC, and how do they differ?
3-axis CNC Machining
3-axis CNC milling remains one of the most prevalent and widely employed machining processes. During 3-axis machining, the workpiece remains stationary while a rotating tool cuts along the X, Y, and Z axes. This constitutes a relatively straightforward form of CNC machining, suitable for producing items with simple structures. It is unsuitable for machining complex geometries or products featuring intricate components.
4-axis CNC Machining
In 4-axis CNC milling, a fourth axis is incorporated into the cutting tool's motion, permitting rotation about the X-axis. There are now four axes: X, Y, Z, and A (rotation about the X-axis). Most four-axis CNC machines also permit workpiece rotation, known as the B-axis, enabling the machine to function both as a milling machine and a lathe.
When drilling holes on the side of a part or on the curved surface of a cylinder, 4-axis CNC machining is the optimal solution. It significantly accelerates the machining process while delivering high machining precision.
5-axis CNC Machining
5-axis CNC milling incorporates an additional rotational axis compared to four-axis CNC. The fifth axis rotates around the Y-axis, also termed the B-axis. On certain machines, the workpiece may also rotate, a function sometimes designated as the B-axis or C-axis.
Owing to its high versatility, 5-axis CNC machining is employed for manufacturing complex precision components. Examples include medical prosthetics or skeletal components, aerospace parts, titanium components, oil and gas machinery parts, and military products.
Comparison: 3-Axis vs. 4-Axis vs. 5-Axis CNC Machining
| Axis Type | 3-Axis | 4-Axis | 5-Axis |
| Machinable Surfaces | 1–2 primary faces | Multiple side faces | Nearly all faces in a single setup |
| Ability to Machine Angled/Curved Surfaces | Angled features require multiple setups; curved surfaces limited | Capable of machining angled surfaces in one rotational direction | Ideal for complex freeform surfaces and multi-angle features |
| Precision | Medium | High | Very High |
| Cost Level | Low | Medium | High |
| Suitable Part Types | Standard components, brackets, plates, simple cavities | Parts with circumferential holes, side features, housings | Aerospace parts, impellers, medical implants, complex geometry components |
3-axis machine tools offer low cost and high versatility, making them suitable for basic machining operations.
4-axis machine tools excel in multi-surface machining and the initial processing of complex surfaces.
5-axis machine tools represent the pinnacle of high-end manufacturing capabilities, being ideal for the machining of high-precision, complex curved components. Selection should be based on a comprehensive assessment of part complexity, precision requirements, and budgetary constraints.