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6-Axis CNC Machining: Simply Explained

6-Axis CNC Machining: Simply Explained

6-Axis CNC Machining: Simply Explained

The number of axes on a CNC machine can greatly affect what projects you can machine on your CNC.

In a CNC, either the tool or the workpiece is moved along different axes to perform the desired machining operation.

3-axis CNC machines are the most basic CNCs and the most popular.

But you can find 4, 5, and even 6-axis CNC machines in various industrial applications.

6-axis CNC machines are relatively rare, but they do exist and are used for extremely precise machining operations.

In this article, I discuss 6-axis CNC machining in-depth.

At the end of the article, I've also discussed 3, 4, and 5-axis CNC machining to help you identify their significant differences from 6-axis machining.

6-Axis CNC Machining

6-axis CNC machining provides freedom to move the cutting tool along 6-axes: three linear axes (X,Y,Z) and three rotational axes (A,B,C). This provides the flexibility to access the workpiece from all 6 sides and perform complex machining operations with high accuracy and quick cycle time.

Axis system used for 6-axis CNC machining
Axis system used for 6-axis CNC machining

However, the development of 6-axis machines did not take place overnight and consisted of a series of sequential developments in the form of 3, 4, and 5-axis systems.

6-axis CNC Machining- How it's different

CNC machining is the process of using a computer-controlled machine to produce the desired cuts in a material.

Typical CNC machines have a 3-axis system in which the cutting tool moves along the X, Y, and Z axes to perform the required machining operation.

These machines are limited to accessing only one face of the workpiece at a time and are therefore ideal for machining flat surfaces.

However, a 3-axis CNC machine can also be used to produce complex shapes by changing the orientation of the workpiece to machine each face of the workpiece.

The introduction of 4-axis CNC machines enhanced the machining ability by providing freedom to move the tool or workpiece along an additional axis.

Therefore, apart from the three linear axes (XYZ), a 4-axis CNC can move either along A-axis (rotation along X-axis) or B-axis (rotation along Y-axis).

This rotary axis provides the ability to work on cylindrical workpieces like pens, shafts, etc., without the need to stop the process and change the orientation of the workpiece.

Furthermore, the introduction of 5-axis CNC machines added another additional axis to the system, thereby enabling the cutting tool to move around the XYZ plane and rotate about any two of these three axes.

As a result, these machines could access the workpiece from multiple sides and produce complex shapes with overhanging elements, without the need to stop and reorient the workpiece.

Although 5-axis machines can perform complex machining operations, the introduction of 6-axis CNC machines revolutionized the manufacturing industry by reducing the cycle time and increasing accuracy.

These magnificent machines provide the ability to traverse linearly in the XYZ plane and rotate along A, B, and C axes.

As a result, a 6-axis CNC machining further enhances the ability to produce highly complex shapes efficiently, quickly, and accurately for unmatched precision.

6-axis CNC machines can perform almost every machining operation without the need for stopping the process to reorient the workpiece.

For example, a 6-axis CNC lathe with a rotary tool can perform turning and milling operations on cylindrical workpieces, making them ideal for cutting gears from a cylindrical stock.

Industries like aerospace, automotive, and alternative energy leverage the advantage of 6-axis CNC machining in their production.

With so many variables at work, it is difficult to imagine the working of a 6-axis CNC machine.

Check out this video from Zimmermann that shows a 6-axis CNC machine in action and compares its machining time with that of a 5-axis CNC machine.

YouTube video
Working and advantage of a 6-axis CNC machine against 5-axis machine

Advantages of 6-axis CNC Machining

6-axis CNC machining process offers various advantages over 3, 4, and 5-axis processes.

Speed

6-axis CNC machines operate at blazing speeds and can manufacture parts with the highest level of precision in minimal time. You can reduce the manufacturing time up to 75% using 6-axis CNC machining.

It is because each X, Y, and Z-axis has its axis of rotation that lets you machine the different sides of a workpiece on a single fixture.

6-axis CNC manufacturing can be extremely expensive but can produce parts in less time, saving production costs.

Therefore, 6-axis CNC machining is generally advantageous for high-volume parts production, where high precision with quick cycle time is desirable.

Machining Operations

6-axis CNC machines are capable of rotating both, workbed and the cutting tool. It means you can perform drilling, milling, grinding, turning, grooving, and parting operations on a single machine.

Machining Complexity Geometry

With 6-axis CNC machines, you can manufacture parts that are large in shape and have highly complex geometry.

Whether you are manufacturing artificial bone, automotive, military weapons, or aircraft parts, 6-axis CNC machining provides extremely high accuracy with quick cycle time, even for complex geometries.

Productivity

6-axis CNC machining delivers fast cutting rates and the best surface finish in part manufacturing, thereby increasing the workflow, productivity, and efficiency.

The added degrees of freedom also provide smooth movement of the workbed and cutting tool, thereby facilitating high-quality machining of flexible curves, like S-curves.

Disadvantages of 6-axis CNC Machining

Although 6-axis CNC machines are ultimate all-rounders that can perform almost any machining operation, there are various limitations associated with these machines.

Cost

The addition of one more axis to a 5-axis system surely enhances its capabilities, but it also increases its cost drastically.

These costs are inculcated in the form of additional parts required for enhanced mobility and special control systems required for the additional axis.

Furthermore, these machines are not readily available on the market and are generally manufactured, based on an order, to meet special requirements, which further increases the overall cost of the machine.

Apart from the cost of the equipment, these machines require special CNC control software that can cost much higher than regular software used for typical 3-axis CNC machines.

As a result, these machines are limited to high-end industrial applications where accuracy and speed are of utmost value.

Need of Expertise

A 6-axis CNC machine can traverse along 3 linear axes and 3 rotary axes, which increases the complexity of the system.

This increased complexity is also reflected in the design phase of the machining process.

Preparing the design of a 6-axis CNC machining process requires an expert machinist to device the toolpaths of such a complex machine.

Furthermore, it is important to run each design through simulation software to avoid collision and prevent the risk of damaging an expensive machine.

Maintenance

With the increase in the complexity and parts of the machine, the maintenance also increases.

6-axis CNC machines consist of a complex structure that requires specialized tools and an expert machinist to perform routine maintenance operations.

Furthermore, certain part replacements or repairs of such complex machines can cost almost equal to the cost of a small-scale CNC machine.

Therefore it is important to perform preventive maintenance of 6-axis CNC machines to minimize the risk of breakdown.

Applications of 6-axis CNC Machining

6-axis CNC machines are all-rounder machines that can perform almost all the machining operations on a single setup.

These machines are ideal for complex machining operations with 3D contours that play a vital role in the performance of the part.

Generally, 6-axis machines are used in aerospace, medicine, and hydropower industries where the accuracy of part geometry plays a vital role.

These machines are used for producing crucial parts such as engine blocks, hydro-power turbines, cockpit, and wings of an airplane.

Popular 6-Axis CNC Machines

ZIMMERMANN FZ100

Zimmermann FZ100 6-axis CNC mill (Sorce: Zimmermann)
Zimmermann FZ100 6-axis CNC mill (Sorce: Zimmermann)

Zimmermann FZ100 is a 6-axis portal CNC mill manufactured by Zimmermann milling solutions. It is an industry-grade CNC machine designed for the complex manufacturing process.

This 6-axis CNC mill is suitable for making parts for alternative energy, automotive, aerospace, and shipbuilding industries.

It has a 156' x 33.3' footprint that provides a cutting area of 131.23' x 19 69' with a Z-axis travel of around 9.8 inches.

The machine table of FZ100 is firmly integrated with the machine's base and has longitudinal T-slots roughly 10 inches apart.

These T-slots are rigid enough to hold a wide variety and sizes of workpieces with a maximum weight of 11,023 lbs.

It has fixed sidewalls on both sides to support the gantry and overhead traveling portal. The gantry travels through rack and pinion drive powered by industry-grade servo motors.

The portal houses a dynamic M3ABC milling head, making the FZ100 the world's first 6-axis portal CNC mill.

M3ABC milling head (Source: Zimmermann)
M3ABC milling head (Source: Zimmermann)

M3ABC is a versatile 3-axis milling head that swivels in A, B, and C axes having ranges of ±100°, ±14°, and ±300°, respectively.

This vast swiveling range of milling heads provides good flexibility for complex CNC machining, such as milling conical parts for the aerospace industry.

Zimmermann offers two different spindle options for milling heads.

One spindle has an 80 hp of power rating and runs at a maximum speed of 22,000 RPM. Another is a 99hp spindle with a full speed of 30,000 RPM.

These spindles are designed for high-speed cutting of ferrous metals, like steel and cast iron.

Both spindles have an HSK-A63 tool holder with spring-based tool clamping.

BACCI Artist.TGV

BACCI Artist.TGV 6-axis CNC machine (Source: BACCI)
BACCI Artist.TGV 6-axis CNC machine (Source: BACCI)

Artist.TGV is a 6-axis CNC router manufactured by Bacci. It is designed to produce large-size products, like doors, windows, chairs, and many more.

Although BACCI is a Germany-based manufacturing company, they also have a branch in the USA for CNC machine sales and customer service.

This CNC machine provides a cutting area of around 102" (X) x 86" (Y) with verticle Z-axis travel of 32 inches.

With unlimited rotation around A-axis, it provides 400° rotation in C-axis.

It has two independent working tables of width around 35 inches. These are variable geometry tables (TGV) that let you machine curved furniture and long curved elements.

TGV tables are integrated with an automatic feed hopper system that simultaneously loads and unloads the workpieces for machining.

The magazines of the feed hopper slide on linear guides. It is helpful to park the hoopers outside the working area while operating the CNC machine in manual mode.

Each table is equipped with steel rails to provide rigidity during heavy-duty CNC machining.

The design of steel rails helps to keep vacuum suction inwards to hold the workpieces on the table with a curved surface. Additionally, it has M8 holes to fix the workpiece.

Another table has steel jigs that are equipped with adjustable height jig clamps. These jigs have pop-up reference stops to hold long curved templates.

You can choose a TGV table with a turning operation for additional lathe functionality, ideal for woodworking applications.

It allows performing indexing and continuous machining to carve intricate designs on round wooden stocks.

On a turning table, you can hold a round workpiece of a maximum length of 51 inches, having a diameter of around 8 inches.

Artist.TGV is equipped with a T2+2 type operating head. The T2+2 means it has two spindles, and each spindle can spin two cutting tools in opposite directions.

The milling head has 10 HP electric spindles with an ER32 collet for cutting tool holding, and independent electronic inverters control the speed of the spindles.

Case Study

Triumph Structures-Wichita is a company of Triumph Group, the global leader in manufacturing parts for the aviation industry.

Although Triumph Structures had more than 20 3-axis and 4-axis CNC machines for aluminum and hard-metal machining to make aircraft parts, they were still looking for a multipurpose CNC machine.

They approached Zimmerman for a CNC machine with two milling heads that could mill long parts, manage material expansion due to volumetric compensation, and deliver an extended duty cycle.

It took around 18 months to address the challenges, and Zimmermann customized one of their popular 6-axis CNC mills, the FZ100.

The results were impressive after the customizations, and they could manufacture aircraft wings up to 80 feet in length.

This customized, twin-head, 6-axis Zimmermann FZ100 improved the product cycle by 35% and helped them achieve improved machining accuracy.

3, 4, and 5-axis CNC Machining and their Limitations against 6-axis Machines

The significant difference between 3, 4, 5, and 6-axis CNC machining is the types of movements that a workpiece and the cutting tool can execute.

Although these CNC machines are powerful tools, they have significant limitations when compared to 6-axis CNC machines.

3-axis CNC Machining

It is a simple machining process where the workpiece remains fixed on a workbed, and a cutting tool traverses in the X, Y, and Z linear directions, left to right, back to front, and up and down, respectively.

For instance, let's look at Shapeoko 3, which is a 3-axis CNC router. It has a fixed workbed and a gantry that houses a cutting tool.

3-axis movement in Shapeoko 3 CNC router (Source: Carbide 3D)
3-axis movement in Shapeoko 3 CNC router (Source: Carbide 3D)

During CNC machining, the cutting tool can traverse X and Y axes with the help of gantry and Z-axis motion through a linear motion component attached to it.

Few CNC routers, like Avid PRO, provide the ability to use two different cutting tools, such as spindle and plasma cutter, at the same time.

This enables you to complete your job in one cycle without changing tools.

3-axis CNC machines are primarily used to manufacture parts that have flat, 2D, and 2.5D geometries.

Applications

3-axis CNC machines have a large user base, varying from hobbyists to full-service production industries.

They are used in various areas, such as woodworking, machining soft materials, non-ferrous and ferrous metal machining.

With 3-axis CNC machining, you can automate the machining process of threaded holes, drilling, slot milling, undercut, circular features (in X-Y plane only), and lining profiles.

Limitations

The 3-axis CNC machining process is capable of removing material from a workpiece in three directions only.

Hence, you can't use them for angular machining to create a feature(s) on an angle with respect to the X-Y-Z coordinate system.

Unlike 6-axis CNC, these machines cannot access all six sides of a workpiece without stopping the machining process and manually rotating the workpiece to access its other surface.

This repositioning increases the cycle time and risk of dimensional errors, thereby leading to reduced accuracy and quality loss in the manufactured part.

4-axis CNC Machining

4-axis CNC Machine
4-axis illustration

In addition to the movement in traditional X-Y-Z axes, 4-axis CNC machines involve one additional axis of machining, i.e., rotation around the X or Y-axis.

This new axis is called A-axis (for rotation around X-axis) or B-axis (for rotation around Y-axis).

CNC manufacturers provide a 4th-axis kit that you can fix parallel to the X or Y-axis for machining. Most of the 4th-axis kits let you perform vertical machining operations.

For example, let's consider the Avid PRO 4896 CNC router. It is a popular 3-axis CNC router that supports a 4th-axis upgrade.

4-axis movement in Avid Pro CNC router (Source: Avid CNC)
4-axis movement in Avid Pro CNC router (Source: Avid CNC)

Avid provides a 4th-axis kit that can be installed either along the X-axis or Y-axis of the CNC system.

This kit has a jaw chuck that holds the workpiece, and a tailstock to keep it in place.

The chuck rotates the workpiece, thereby providing access to four sides with a single setup of work holding.

Applications

4-axis CNC machining can be used to produce parts with intricate designs, that are often difficult to machine with a 3-axis system.

The additional axis of rotation allows you to make intermittent cuts on workpieces. You can drill and engrave around a curved surface, like a cylinder or sphere.

You can also do index machining to manufacture nuts, bolts, washers, pins, and continuous machining to produce helix geometry and complex profiles in Cam lobes.

The 4th-axis kit lets you make an angled feature, intricate cuts, and contours using a single fixture set up for the workpiece.

Unlike 6-axis CNC machines, these machines cannot access the workpiece from all sides and are therefore limited to performing the above-mentioned operations only along the single axis of rotation.

Performing these machining operations around a different axis of rotation requires reorientation of the workpiece and the 4th-axis kit.

5-axis CNC Machining

5 Axis CNC Machine
5 Axis CNC Machine

5-axis CNC machining utilizes traditional X-Y-Z axes and two of the three available rotational axes. These two axes of rotation are used to have a rotating workbed or for router/spindle movement.

Usually, CNC machines use either A and C-axes or B and C-axes for rotation.

Let's take an example of the world's smallest 5-axis desktop CNC mill, Pocket NC V2-10.

Besides movement in traditional X, Y, and Z axes, it has two rotary axes, namely, tilt and rotation.

5-axis movement in PocketNC V2 CNC router (Sorce: Pocket NC)
5-axis movement in PocketNC V2 CNC router (Sorce: Pocket NC)

Generally, 5-axis CNC machines are of two types: 3+2 CNC machines and fully continuous 5-axis CNC machines.

In 3+2 machines, the two rotational axes cannot operate simultaneously. It means you can fix the position of one rotational axis and utilize the other rotational axis, along with X-Y-Z axes, to perform the required operation.

Whereas in fully continuous 5-axis CNC machines, you can perform machining operations using both the rotational axes simultaneously with the cutting tool movement in the X, Y, and Z axes.

Applications

You can create parts with complex 3D geometries, such as helical rotors using both 3+2-axis and continuous 5-axis CNC machines.

Additionally, a 3+2-axis CNC machine can produce parts with angled features. If you want to make parts with compound angled features, you can use continuous 5-axis CNC machines.

The simultaneous operation of two rotational axes lets you perform the molding process. Hence, you can also produce 3D shapes with complex curved surfaces.

5-axis CNC machine can perform almost all the operations of a 6-axis CNC machine but with slightly lower accuracy and significantly longer cycle time.

However, for applications that involve machining of vertical slots on different sides of the workpiece, a 5-axis CNC machine can produce similar results to a 6-axis machine at a lower cost.

Final Thoughts

3-axis CNC machines have simple operations and are the primary form of CNC machining.

The addition of the axis of rotation around the X, Y, and Z axes increases manufacturing speeds and lets the CNC machine process various shapes for machining.

However, the addition of rotational axes also increases the complexity of the design and control of the machining operation.

Although 5-axis CNC machining is widely used to produce parts with complex shapes and angled features, 6-axis CNC machining is a boon to manufacturing industries as it provides blazing speed, productivity, accuracy, and efficiency.

6-axis CNC machining technology is continuously evolving and will be widely used in large-scale production industries in the near future.

Frequently Asked Questions (FAQ)

Can you suggest a low-cost CNC controller software for 6-axis CNC machining?

You can use UCCNC CNC controller software. It is easy to use and works smoothly with up to 6-axis CNC machining. This software will cost you around $60.

What are the limitations of 6-axis CNC machining?

6-axis CNC machining is a highly complex operation that requires an experienced and skillful machinist to operate. The design and control of a 6-axis machining process involve a number of variables which increases the overall complexity of the process. Furthermore, 6-axis CNC machines are comparatively expensive and therefore are limited to high-end industrial applications only.

What operations can a 6-axis CNC machine perform?

6-axis CNC machines are highly versatile and can perform almost every machining operation, provided the availability of appropriate cutting tools. Certain 6-axis CNC machines have the ability to rotate the cutting tool and the workpiece, making them a combination milling and lathe machines.

About John

Hey I'm John. I talk about CNCs and Lasers at Mellowpine. If you have any questions related to CNCs or Lasers, I'd be happy to answer them. Reach me at mail@mellowpine.com

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John

Hey I'm John. I talk about CNCs and Lasers at Mellowpine. If you have any questions related to CNCs or Lasers, I'd be happy to answer them. Reach me at mail@mellowpine.com

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