Difference Between CNC Machine Axes

CNC machines use a variety of different axis counts. But having more axes on a device is not necessarily better. Understanding the different axes of CNC machines and their applications will make it easier to select the best machine for your purposes.

What Is CNC Machining?

CNC machining, short for computer numerical control machining, uses a computer program to direct cutting tools in manufacturing. This method encompasses various techniques that can be controlled by a computer program. It’s important to differentiate between the CNC machine and the software used to control it, commonly known as computer-aided machining (CAM) or computer-aided manufacturing. While the CAM software translates images into a language that the CNC machine can understand, the CNC system instructs the machine on what actions to take based on the code from the CAM design.

Screw machining, milling and turning are some of the applications of CNC machining. Once the part is programmed, the CNC machine moves the cutting tools along multiple axes to achieve precise cuts. Automating the process helps minimize concerns related to human error. However, it still requires a skilled professional to select the appropriate tools and make decisions to obtain the desired finish. A proficient controller must consider numerous factors, including the type of end mills, materials used and the number of axes involved. These considerations highlight the expertise needed to operate a CNC machine effectively and optimize its performance.

Different CNC Machine Axis Counts

CNC axis counts can range from three to five. More does not necessarily make for a better project, though. Choosing the right number of axes to balance cost and finish is an integral part of machining. All machines start with three axes. The three axes model performs essential functions and, in the hands of an experienced machinist, can be used for more advanced creations. Four axes on a CNC machine add an extra cutting direction, which increases precision. The fifth axis further improves the accuracy of the machine, but the cost of the five-axis CNC machine makes it too expensive for most businesses. Additionally, the extra cost is unnecessary for most applications aside from the most intricate parts used in highly specialized industries.

When selecting the type of machining needed, three-axis machining suffices for most. For specific projects, though, you may need a rare use of a four- or five-axis CNC machine. Generally, the part’s geometry will help determine how many cutting axes you need. For instance, deeper or more intricate parts require four or five axes in most cases. But even something as delicate as a turbine blade can be produced with three axes with the right operator who knows how to properly index the edge.

Remember, too, that the more axes a CNC machine has, the more preparation time the project will require. Consider this when choosing the number of axes you want to use for your project.

What Is Three-Axis CNC Machining?

Three-axis machining cuts along an XYZ plane: X axis (vertical), Y axis (horizontal) and Z axis (depth). Think of the x-axis as “left to right,” the y-axis as “forward to backward” and the z-axis as “up and down.” These traditional machines have a simpler setup compared to four- and five-axis machines. But three-axis machines also require the operator to have more knowledge in achieving the desired result and how to position or reposition the material.

Unlike other means of crafting parts, three-axis CNC machines only need one workstation to complete the task. By reducing the movement of the part throughout a workshop, the part’s creation time drops and precision increases, since a single machine does everything by a carefully controlled computer.

The ideal situation in which to use three-axis CNC machining is when cutting into a shallow piece of material. But there are uses beyond that when in the hands of a well-trained, experienced user. Some standard applications for three-axis machining include milling slots, drilling and creating edges:

• Milling slots: Three-axis machines excel at cutting slots into various materials. This capability is particularly useful in applications such as furniture manufacturing, where interlocking pieces need to fit precisely together. With the ability to cut well-defined slots, three-axis machines ensure the accurate alignment and secure assembly of parts.
• Drilling: By precisely positioning the cutting tool, these machines make creating holes for screws or other fasteners easier. The ability to drill accurately and consistently enhances the efficiency of assembly processes and ensures the structural integrity of the final product.
• Cutting sharp edges: Three-axis machines are adept at edging materials, allowing for the creation of angled surfaces and sharp corners. Whether chamfering, beveling or creating intricate edge profiles, these machines offer the precision necessary to achieve clean and defined edges quickly and efficiently.
• Creating customized parts: Three-axis machines are simple and easy to use, making them accessible even to those with limited machining expertise.

There will be some situations where three-axis machines may not suffice. Though rare, some cases will require the use of four- or five-axis machines. As these machines are harder to find and cost much more, they should only be used for highly technical work that requires additional axes.

What Is Four-Axis CNC Machining?

Four-axis machines employ another means of cutting by moving the cutter around the vertical axis. The advantage of this additional cutting direction is increased intricacy in the finished product. Because these machines have an extra cutting direction, they cost more to purchase. In many instances, this additional cost gets passed on to the customers of CNC machine operators. Like three-axis machines, the four-axis design has specific uses, but the four-axis style requires more programming at the beginning to get the system set up to create the cuts.

Four-axis CNC machines may cut along all four axes at the same time or along the x, y and z axes simultaneously and around the vertical axis separately. These two designs for four-axis machines could affect production time. The more axes cut at once, the faster production goes. This more rapid workflow is one way three-axis CNC machines have an advantage over some four-axis CNC devices.

Due to the creation of five-axis machines, four-axis designs have fallen by the wayside. Additionally, many skilled machinists can create what they need with three-axis devices, which cost less, rather than purchasing the more expensive and complicated four-axis machines. Consider these applications when deciding:

• Industrial parts: Complex industrial parts often demand intricate details and specific cutting requirements. These parts are frequently proprietary to the companies using them, necessitating custom creation to meet their unique specifications and functional needs.
• Prototypes: Four-axis CNC machines fabricate prototypes, allowing stakeholders to visualize and evaluate smaller-scale models of their envisioned products in three dimensions. This iterative process aids in refining designs and identifying potential improvements before committing significant resources to full-scale production.
• Education: Four-axis CNC machines offer educators a tool to teach the fundamentals of CNC machining without the expense of training on a more complex five-axis unit. These machines can also create customized teaching supplies and demonstration models, which are often unavailable for purchase from standard suppliers.
• Medical equipment: Four- and five-axis CNC machines are sought-after for companies producing specialized medical equipment. The intricate designs and tight tolerances required for medical devices are well-suited to the capabilities of these advanced machines, ensuring the highest levels of accuracy, reliability and quality in the final products.

What Is Five-Axis CNC Machining?

Adding a fifth axis to a four-axis machine further increases the potential applications of the machine. These machines have better precision and require less movement of the original material. Since the material only needs positioning once, lead times get shorter. However, depending on the machine’s configuration, the overall time could be the same or longer than with simpler devices.

Five-axis machines may have one of three common configurations. The “four plus one” style has four axes that run at once, and the fifth has a separate control. “Three plus two” designs have three axes that move simultaneously, while the other two can be controlled separately. True five-axis machines operate all five axes at once. The last model is much more expensive, but it works faster. Compared to three- and four-axis machines, five-axis designs can use shorter tools, which gives these machines their precision.

Thanks to the extra axis of rotation, five-axis machining is used for creating designs that rely on extreme precision. These products are typically used in highly specialized industries where accuracy can mean the difference between life and death. Medicine, military, aerospace, petrochemical and other fields often use five-axis machining to create their custom parts:

• Medical components: Any flaws in cuts or edges can render medical supplies unusable and compromise patient safety. Five-axis machining is the preferred method for creating customized medical tools and components, creating the level of accuracy and reliability required for critical applications in the health care industry.
• Automotive design: Modern vehicles rely on mechanical and electronic systems, necessitating precise fitting of mechanical parts and intricate electrical housings. Five-axis machines ensure the proper fit and alignment of mechanical components while also facilitating the machining of complex electrical parts that may require the capabilities offered by higher-axis CNC machines.
• Architectural components: Architectural designs involve puzzle-like structures where every component must fit perfectly with one another. Even a minor error in a cut can significantly compromise the overall design and jeopardize compliance with building regulations. Five-axis machining is often employed to create architectural components, such as door frames, which require precise cutting and intricate detailing to maintain the integrity of the design.
• Military-grade products: The military industry prioritizes consistency and precision in their vehicles, weapons and other products. Quality control and reliability are critical in military applications. Five-axis machining ensures the highest level of accuracy and adherence to strict specifications, enabling the production of military-grade products that meet the rigorous standards required for defense and security purposes.
• Petrochemical industry parts: The petrochemical industry relies on customized components for oil rigs, refineries and other facilities. These parts often have specialized requirements that demand advanced machining capabilities. Five-axis machining creates petrochemical industry parts, providing the necessary precision and complexity to manufacture components not readily available in stores.
• Aerospace Components: The aerospace industry operates under rigorous standards to ensure the safety and reliability of airplanes, rockets, satellites and other spacecraft. The precision required in aerospace manufacturing is paramount, as even the slightest imperfection can have severe consequences.

While five-axis CNC machines are useful for the above applications, some of them may be achieved using a three-axis machine with the right operator who is skilled in positioning the material and moving it to create cuts on different axes. Opting for a trained expert using a three-axis machine offers several advantages whenever you need custom parts created.

Benefits and Limitations

With CNC machining, the number of axes plays a significant role in determining the capabilities and limitations of the machine. Three-, four- and five-axis CNC machines possess unique attributes that impact the shapes and geometries they can machine, the precision levels achievable and the complexity of programming and setup.

Benefits of Three-Axis CNC Machining

Benefits and Limitations of Three-Axis CNC Machining

Here are some of the benefits of three-axis CNC machining:

• Simplicity: Three-axis machines are easier to program and set up due to their straightforward configuration.
• Versatility: They can effectively produce a wide range of flat and prismatic parts, making them suitable for many applications.
• Cost-effectiveness: By lowering the time requirements for creating custom parts, three-axis machines cut project costs considerably versus using multiple workstations to make a single component.
• Increasing efficiency: Settings allow for the cutters to only move through the parts of the material yet to be cut. This design prevents the cutters from going past the material and into the air, which wastes time and reduces efficiency.

While three-axis CNC machines have their merits in terms of simplicity, versatility and cost-effectiveness, it is important to acknowledge their limitations. These limitations primarily revolve around the restricted range of motion and its effect on the achievable complexity of shapes and precision levels.

• Restricted geometries: Due to the limited range of motion, three-axis machines are better suited for machining simpler shapes and geometries, such as flat surfaces and box-like structures. Three-axis machines struggle to machine undercuts and overhangs effectively.
• Limited precision: Due to the restricted degrees of freedom, achieving intricate details and high precision may be challenging with three-axis machines.

Benefits and Limitations of Four-Axis CNC Machining

Four-axis CNC machining adds an additional rotational axis, which imparts enhanced flexibility and machining capabilities. Here are some of the benefits of a four-axis machine:

• Increased complexity: With the addition of a rotational axis, four-axis machines can produce more complex shapes and geometries, including cylindrical and contoured parts.
• Increased machining access: The rotational axis in four-axis machines provides improved access to complex features and surfaces of a workpiece. It enables the machine to reach difficult-to-access areas, producing more comprehensive machining capabilities.
• Reduced setup time: The ability to rotate the workpiece allows for machining from multiple angles, minimizing the need for repositioning and reducing setup time.
• Enhanced efficiency for indexed machining: With the addition of a rotational axis, four-axis machines excel at indexed machining. This capability allows for efficient machining of multiple sides of a workpiece without repositioning, reducing overall production time.

Four-axis CNC machines offer increased versatility and the ability to produce more complex shapes and geometries than their three-axis counterparts. However, the level of precision achieved may not be on par with three-axis machines, creating some limitations.

• Programming complexity: Including a rotational axis adds complexity to the programming process, requiring more sophisticated tool paths and positioning calculations.
• Moderate precision: While four-axis machines offer more versatility, achieving the same level of precision as three-axis machines can be more challenging due to the increased complexity.
• Reduced stability: A rotational axis can introduce additional vibrations and instability during machining, especially when working with longer tools or heavy workpieces.

Benefits and Limitations of Five-Axis CNC Machining

Five-axis CNC machining takes versatility to new heights by introducing two additional rotary axes, typically labeled A and B. This configuration enables machining from multiple angles with exceptional precision.

• Unmatched versatility: Five-axis machines excel in producing complex, free-form shapes and intricate geometries. They allow for simultaneous machining from various angles, enhancing productivity and reducing production time.
• Reduced setup time: With their ability to machine from multiple angles, five-axis machines minimize the need for repositioning or multiple setups. This reduction in setup time translates to increased productivity and shorter lead times.
• Eliminating specialized fixtures: More axes allow for machining parts from more orientations, eliminating the need for complex or specialized fixtures. This flexibility reduces tooling costs and setup complexity.
• Superior precision: The multi-axis capability empowers these machines to achieve exceptional accuracy and surface finish, making them ideal for high-precision applications.

Five-axis CNC machines still come with a few limitations.

• Higher Complexity: Programming and setup for five-axis machines are significantly more intricate and time-consuming. Advanced knowledge of multi-axis machining strategies and software is required, which can result in longer setup times and increased programming complexity.
• Cost: Five-axis machines are generally more expensive than their lower-axis counterparts. The advanced design and additional axes contribute to higher upfront costs and potential maintenance and repair expenses.

Find the Right Axis Type for Your Needs

You don’t have to be alone in your CNC machining projects. At American Micro Industries, we have the computer systems and equipment needed to machine your parts accurately and as quickly as possible. Our machining professionals will do everything we can to fulfill your custom part designs. Contact us at AMI for a quote for all your CNC machining needs. We’ll take the pressure off you as we do our best to complete your project to the best of our abilities. Let us know how we can help you by filling out a quote request today.