Comparison of 3 axis, 4 axis, and 5 axis CNC engraving machines

Understanding the three-axis, four-axis, and five-axis configurations of CNC engraving machine kits

5-axis: XYZAB, XYZAC, XYZBC (the spindle can rotate approximately 180° to the left and right)

4-axis: XYZA, XYZB, XYZC (4-axis interpolation)

4th axis: YZA, XZA (4-axis interpolation)

3-axis: XYZ (3-axis interpolation)

The A, B, or C axes correspond to the X, Y, and Z rotation axes, respectively.

Three-axis CNC engraving machine

X-axis: Left to right

Y-axis: Front to back

Z-axis: Up and down

The three-axis CNC engraving machine moves all three axes simultaneously: the X-axis, Y-axis, and Z-axis. Cutting along the X-axis causes the engraving machine's drill bit to move from left to right, cutting along the Y-axis causes it to move from front to back, and cutting along the Z-axis causes it to move up and down. These machines are primarily used for cutting flat, 2D, and 2.5D components. Whether it's flat engraving or circular engraving, you can consider it flat engraving, as it is calculated based on pulses.

Four-axs CNC engraving machine

The workbench of a 4-axis CNC engraving machine can operate on both sides, while the workbench of a 3-axis CNC engraving machine cannot. A 4-axis CNC machine tool also has X, Y, and Z axes, which refer to XYZA, XYZB, and XYZC. The four axes are linked and can operate simultaneously.

Five-axis CNC engraving machine

These engraving machines are somewhat similar to 3- and 4-axis CNC machine kits, but they have two additional movable axes. Since these additional axes can cut five edges of the material simultaneously, project time can be reduced. However, due to the longer X-axis of these machines, stability and accuracy are lower—they may require more attention than 3- and 4-axis CNC engraving machine kits.

The 5-axis CNC machining center features high efficiency and precision, enabling the machining of five surfaces with a single setup of the workpiece. When equipped with a high-end 5-axis CNC system, it can also perform high-precision machining of complex spatial surfaces, making it particularly suitable for the production of modern molds such as automotive components and aircraft structural parts. The rotary axis of a 2-axis vertical machining center has five configurations. One type is the worktable rotary axis, where the worktable mounted on the bed can rotate around the X-axis, defined as the A-axis. The typical operating range of the A-axis is from +30 degrees to -120 degrees. There is also a rotary workbench in the center of the workbench, which rotates around the Z-axis at the position shown in the diagram, defined as the C-axis. The C-axis rotates 360 degrees. Thus, by combining the A-axis and C-axis, except for the bottom surface of the workpiece fixed on the workbench, the remaining five surfaces can be machined by the vertical spindle of the 5-axis machining center. The minimum division value for the A-axis and C-axis is generally 0.001 degrees, enabling arbitrary angle subdivision of the workpiece, such as machining inclined surfaces and inclined holes. If the A-axis and C-axis are linked with the X, Y, and Z linear axes, complex spatial curved surfaces can be machined. Of course, this requires support from high-end CNC systems, servo systems, and software. The advantage of this configuration is that the spindle structure is relatively simple, the spindle rigidity is excellent, and the manufacturing cost is relatively low. However, the worktable cannot be designed to be too large, and its load-bearing capacity is relatively small, especially when the A-axis rotation is greater than or equal to 90 degrees, as the workpiece generates significant load-bearing torque on the worktable during machining. Another method relies on the rotation of the vertical spindle head, with the spindle front end serving as a rotary head that can rotate 360° around the Z-axis to form the C-axis. The rotary head also includes an A-axis that can rotate around the X-axis, typically achieving ±90 degrees or more, thereby achieving the same functionality as described above. The advantage of this configuration is that the spindle offers high flexibility in machining, and the worktable can be designed to be very large. This allows for the machining of large aircraft fuselages and engine casings on such machining centers. Another significant advantage of this design is that when using a spherical milling cutter to machine curved surfaces, if the tool centerline is perpendicular to the machined surface, the linear speed at the tool tip is zero, resulting in poor surface quality at the tip. By adopting a spindle rotation design, the spindle rotates relative to the workpiece by a certain angle, allowing the spherical milling cutter to avoid cutting at the tip and ensuring a certain linear speed, thereby improving surface machining quality. This structure is highly popular for high-precision curved surface machining of molds, which is difficult to achieve with rotary table-type machining centers. To achieve high rotational precision, high-end rotating axes are equipped with circular encoder feedback, with positioning accuracy within a few seconds. Of course, the rotational structure of such spindles is relatively complex, and the manufacturing cost is also higher.

Which CNC engraving machine is best for you?

Although the functions of these engraving machines may seem somewhat basic, they are highly precise and advanced technologies. If you wish to design more creatively, we recommend investing in a four-axis or five-axis CNC engraving machine kit; however, three-axis or four-axis CNC engraving machine kits are typically more cost-effective.

Now that you understand how engraving machines work, you can better grasp the differences between various models.

Five-axis CNC machines have three additional axes compared to two-axis CNC machines. These milling machines can simultaneously cut five sides of a single material, thereby expanding the operator's capabilities and flexibility. Unlike three-axis machines, these machines are typically used for cutting large 3D parts. Additionally, five-axis CNC machines have taller gantries and longer X-axes, enabling them to cut larger parts; however, this comes at a significant cost; the taller the gantry and the longer the X-axis, the lower the machine's precision and stability. To ensure proper quality control, the height of the gantry (h8) and the length of the X-axis should be kept to a minimum whenever possible.

Although engraving machines may appear to be simple machines, they are highly complex technologies that require specialized knowledge to operate. Five-axis CNC machines are often more expensive than traditional three-axis types, but ultimately offer greater flexibility and enable users to be more creative in their designs.

How many axes do you need?

As is often the case in manufacturing, the answer to this question depends on your specific application. Consider the following example:

Turbine blades are free-form surfaces that can be quite complex. The most efficient way to finish these blades is to use five axes, allowing the tool to move in a spiral pattern along the blade's airfoil. If you index the blade to a specific position and then use three linear axes for surface machining, you can use a three-axis setup, but this is typically not the most efficient approach.

The part's geometry will determine whether you need a three-, four-, or five-axis configuration.

However, it is important to remember that the number of axes required is not solely determined by a single part. The part itself plays a significant role, but it also depends on the tasks the workshop aims to accomplish.

A customer might bring me a part, such as a titanium alloy aircraft bracket, and I might say, “This is the perfect part for a five-axis CNC milling machine,” but they might be planning to manufacture parts that work better on one of our other machines. That multi-functional machine may not be optimized like a five-axis CNC machine, but it might offer the customer the opportunity to perform lathe, axis, or chuck machining, which is part of their long-term plan.

Another consideration is the work envelope—what is the maximum part size you can load into the machine while still allowing for tool changes and part transfers? This is about understanding the capabilities of the CNC machine and what it can and cannot do.