What Are 3-axis, 4-axis and 5-axis Machining Centers?
The term “axis count” refers to the number of motion degrees of freedom a machine tool has.
The most common type is the 3-axis machining center, which features X, Y and Z linear axes. It can only machine one plane at a time. A multi-head precision engraving machine, for example, is mainly used to process simple flat surfaces.
However, when you see a machine with 3-axis motion, you should distinguish between a machining center and a CNC milling machine—many people confuse the two. In fact, machining centers are a type of CNC milling machine, but not all CNC milling machines are machining centers. The key difference lies in whether the machine is equipped with an automatic tool changer (ATC).
That’s why the world’s first CNC milling machine, developed by the Massachusetts Institute of Technology (MIT) in 1952, was not a machining center. It was not until 1958 that America’s Kearney & Trecker Corporation developed the first machining center capable of performing all processes including drilling, milling, boring, reaming and tapping.
Driven by market demands and technological advances, 4-axis machining centers emerged. They add one rotary axis to the 3-axis setup: an A-axis if it rotates around the X-axis, or a B-axis if it rotates around the Y-axis. Horizontal machining centers are typical examples. When purchasing, make sure to confirm whether the machine has 4-axis simultaneous machining capability, rather than just “having a 4th axis”.
Next comes the high-end category: 5-axis machining centers. Equipped with two rotary axes, they can machine any surface of a workpiece in a single setup. Besides vertical bottom-face machining, they can handle side and angled side machining.
Their working principle relies on the control system to coordinate the movement of all 5 axes, enabling high-precision and high-efficiency machining. As high-tech, high-precision equipment, 5-axis machining centers can perform operations like hollowing, drilling, angled drilling and bevel cutting on complex curved surfaces, spatial surfaces and special-shaped parts—all with a single suitable tool holder.
Now, here’s the question: A workpiece has 6 faces, so why aren’t there 6-axis simultaneous machining centers?
