What is 4-axis CNC Machining

The reference to axes is used to describe CNC machines that operate along multiple axis points. CNC machining is the process of removing material from a workpiece until the desired shape is configured. These machines have at least 3 axes and operate along an XYZ plane: An x axis (vertical), a Y-axis (horizontal), and a Z-axis (depth). The 4th axis denotes the inclusion of an A axis (rotation around the X axis), and the 5th axis denotes the B axis (rotation around the Y axis).

Based on the limitations of the 3-axis, 4-axis, and 5-axis CNC machining became more popular. The 4-axis CNC machining process encompasses the same mechanism of action. However, from its name, there is an additional axis included.

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4-axis CNC machines generally have more power and higher accuracy than 2-axis or 3-axis machines. The increased accuracy can be attributed to the movements of the fourth axis which rotates around the vertical axis, which gives it a 360-degree range of motion.

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What is 4-Axis CNC Machining?

Also referred to as a 4-axis CNC mill or 4-axis CNC router, it is a computer numerical control machine that can move its tooling in four directions: up and down, left and right, and forward and backward. This allows it to create three-dimensional objects by cutting away material from a block of material. This can also help to develop four-sided objects from flat material.

The dimensions of a 4-axis CNC machine are typically around 3-4 feet wide, 5-6 feet deep, and 7-8 feet tall. They are much larger than 3-axis machines, which usually have a footprint of only 6-8 feet by 3-4 feet.

4-axis machining implies that a workpiece is processed in the same way it would be with a 3-axis machine, but has an additional rotary movement around the X-axis, which is named the A axis. This rotation allows the workpiece to be cut around the B axis. This method is beneficial when holes or cuts need to be made on the sides of a workpiece. The addition of a fourth axis (A axis) allows a workpiece to be automatically flipped over, so the machine can remove material from both sides. 4-axis machining is multifunctional and can be used for:

  • Continuous cutting
  • Intermittent cutting
  • Engraving curved surfaces

Types of 4-axis CNC Machining

There are many types of 4-axis CNC machining, but the indexing and continuous are the most two popular.

Essentially, indexing means holding your part stationary while the tool rotates along the fourth axis. The process of indexing allows you to reach areas that would otherwise be difficult or impossible to access with a traditional setup.

Continuous machining simply means that there is no downtime, which means a single piece of stock can be cut over and over again while the machine is running. The device can cut material simultaneously with the A-axis rotation.

And there are hybrid types of 4-axis CNC, which combines the benefits of both 2- and 3-axis machining. In these cases, the parts will be cut on one axis and then moved to a second axis to mill and drill.

The Types of Projects Best Suited for 4-Axis CNC Machining

There are kinds of projects that are best suited for 4-axis CNC machining. One combined project is fabricating custom parts or components for machinery. This could involve creating replacement pieces to improve efficiency or performance. This could also involve creating parts that are required to complete the manufacturing of an appliance. Other common projects like 3D modeling and printing, making prototype or concept models, and the production of custom carvings.

One more application of 4-axis CNC machining is fabricating custom tools or dies. This could involve creating a custom tool or die for a specific application or manufacturing process. For example, it may be necessary to create an eccentric tool or die to precisely finish a surface, such as the bottom of a gear. In this example, a 4-axis CNC machining center could be programmed to machine one side of the part, then rotate the part 90 degrees and machine the other side using the same setup.

Aerospace is also a field that uses 4-axis CNC machining. Typical aerospace machining involves turning, milling, drilling, and other processes. This high precision of this type of machining is particularly desirable for machining the many tiny gears used in aircraft and spacecraft.

Choosing Between 4-axis and 3-axis CNC Machining

A few factors to consider when you choose between 4-axis and 3-axis CNC machining:

  • The complexity of the part: Complex parts are better suited for 4-axis machining because it allows more movement that can create more complex shapes.
  • Size of the part: Parts that are larger in size are better suited for 4-axis machining because they can accommodate the size of the part and produce a more accurate result.
  • Parts precision and accuracy: 4-axis machines are typically more accurate than 3-axis machines. Because it is easier to stabilize all three axes on a 4-axis machine.
  • Tooling: 3-axis machines are better suited for softer tooling like sanding belts, spindles, and drill jigs. Because these types of tooling have more flex in them which can make the tooling more susceptible to fractures and bending.
  • Durability: 3-axis machines are better suited for light-duty, higher-speed machining works. Because it allows for a smaller cutter head and fewer vibrations that can occur during machining.

What is the difference between 4 and 5 axis CNC?

The core distinction between 4-axis and 5-axis CNC machining lies in the additional axes that the latter possesses, leading to more subtle differences between the two.

Difference in Axes
4-axis CNC machining has an extra axis, the A-axis, while 5-axis CNC machining has two extra, which can be A-axis, B-axis, or C-axis depending on the configuration.

Through the utilization of 4-axis CNC machining, rotation on the A-axis is made ture. With 5-axis machining, however, rotation is allowed on two of the three axes – the A-axis, B-axis, and C-axis.

CNC Machining Flexibility
Compared to 4-axis CNC machining, 5-axis CNC machining has the added benefit of an additional axis that is not restricted to the X-axis. The capability to rotate on two of the XYZ axes grants 5-axis CNC machining a higher degree of flexibility, thus allowing it to have an edge over its 4-axis CNC machining.

CNC Machining Cost
By comparison, 5-axis CNC machining offers more advanced functions and features, such as the ability to maneuver the cutting tools from multiple angles and in different directions. This ultimately provides more complex machining operations, as well as greater precision, eliminating the need for multiple setups, thus increasing its cost in comparison to 4-axis CNC machining.


The addition of a 4 axis allows for greater flexibility and control of the cutting process, resulting in increased accuracy and precision. 4-axis CNC machining includes indexing, continuous machining, and hybrid types. 4-axis CNC machining is suitable for the manufacture of custom parts or components for machinery, as well as for the manufacture of parts needed to complete electrical manufacturing.

The addition of a 4 axis allows for greater flexibility and control of the cutting process, resulting in increased accuracy and precision. 4-axis CNC machining includes indexing, continuous machining, and hybrid types. 4-axis CNC machining is suitable for the manufacture of custom parts or components for machinery, as well as for the manufacture of parts needed to complete electrical manufacturing.

What are the advantages of 4-axis CNC machining?

4-axis CNC machining offers several advantages, including increased flexibility, accuracy, and efficiency. With the ability to machine on multiple sides or angles, 4-axis CNC machines can reduce the number of setups required, saving time and reducing the potential for errors. Additionally, the rotary axis enables more complex geometries to be machined, increasing design options and capabilities.

What materials can be machined with 4-axis CNC machining?

4-axis CNC machining can be used to machine a wide variety of materials, including metals, plastics, composites, and wood. The specific material and its properties will determine the appropriate cutting tools, speeds, and feeds for the machining process.

What industries use 4-axis CNC machining?

4-axis CNC machining is used in many industries, including aerospace, automotive, medical, and manufacturing. It is commonly used for producing complex parts, such as turbine blades, medical implants, and molds. Its versatility and flexibility make it a valuable tool for any industry that requires precision manufacturing.

What are the limitations of 4-axis CNC machining?

One limitation of 4-axis CNC machining is that it may not be suitable for certain geometries or materials that require more complex machining operations. Additionally, the rotary axis can add complexity to the programming and setup of the machine, which may require more specialized training or expertise. Finally, 4-axis machines may be more expensive than traditional 3-axis machines, which can impact the cost-effectiveness of the machining process for some applications.

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