From 3 Axes to 12 Axes: A Comparative Analysis of CNC Milling Machine Capabilities

Numerical Control by Computer (CNC) machining seamlessly integrates the effectiveness of computer programming with the adaptability of subtractive manufacturing. The CNC controller collaborates with mechanical elements like axes, motors, and drive components to automatize the production process while upholding quality and repeatability.

In 2024, a variety of CNC machines are available in the market. Contemporary CNC Milling Machines with multiple axes offer a diverse array of features that enhance their value and functionality. Nevertheless, these features prove beneficial only when the machine can navigate smoothly along its axes. Additionally, the accuracy in shaping the feed is predominantly upheld by these axes. Essentially, they serve as the vital components ensuring the precision of any milling machine.

This article will examine and contrast the functionalities and capabilities of different multi-axis CNC milling machines.

3-Axis CNC Machining

Derived from rotary filing (imagine a dental drill 😬), 3-axis CNC machining involves keeping the workpiece stationary while the cutting tool traverses along the X-, Y-, and Z-axes. The X-axis (vertical) moves from left to right across the lathe table, the Y-axis (horizontal) extends from the front to the back of the table, and the Z-axis (depth) is marked by the spindle dropping from the top. In a typical 3-axis CNC milling machine, the table facilitates movement along one or two planes, while the tool handles the remaining planes of motion.

3-axis machines are well-suited for uncomplicated tasks that do not demand intricate detailing or depth. Consequently, it stands out as one of the most favored methods for fabricating mechanical parts utilized in automation. Moreover, it is effective for operations like cutting sharp edges, boring, milling slots, tapping, and drilling holes.

Limitations: However, 3-axis machining is accompanied by the following constraints:

Reduced precision in feature accuracy Diminished capability for intricate machining Decreased potential for complex machined surfaces due to restricted tool access to the part (limited freedom of movement)

4-Axis CNC Machining

Similar to its 3-axis counterpart, a 4-axis CNC machine operates with the workpiece in a stationary position while the cutting tool removes material to shape the desired part.

However, in 4-axis machining, an additional axis of rotation is introduced to the standard X, Y, and Z planar movements. This supplementary movement occurs along the X-axis, creating a fourth plane known as the A-axis. The rotation can be achieved by moving either the tool or the workpiece, and the axis of rotation may be parallel or perpendicular to the tool surface. The orientation of the rotation axis determines the ease of machining certain features, such as undercuts, on a given machine.

4-axis milling proves valuable for tasks such as cutting holes, following arcs, carving cutouts—particularly on the sides or around a cylinder—and executing high-quality, precision engravings, milling, and drilling.

Limitations: The primary limitation of the 4-axis milling machine lies in its Geneva Mechanism. Although this mechanism is appreciated for its simplicity, reliability, and precision, it restricts the 4th axis in practice. These machines cannot support continuous machining due to a fixed set of stops, rendering them suitable only as pure indexers.

Additional drawbacks include:

  • Rapid wear and tear of the worm gear mechanism, especially under high-intensity usage.
  • The issue of backlash, which can impact accuracy and machine durability.

5-Axis CNC Machining

Witness the precision of a 5-axis CNC machine in action. The 5-axis CNC milling machine represents the epitome of innovation in 21st-century machining. It stands as a precise, high-speed, and precision machining powerhouse.

In this configuration, the X, Y, and Z-axes mimic the layout of a 3-axis machine. The table then undergoes rotation along the A-axis, similar to the 4-axis. However, the 5-axis machine introduces a pivotal action at the table joint, followed by rotation along the C-axis, defining the fifth movement. This operates along the following motion paths:

X-axis translation Y-axis translation Z-axis translation A-axis rotation C-axis rotation

5-axis machining empowers the operator to simultaneously address five different sides (or more!) of a part, contingent on the design complexities. Consequently, the tool is adept at crafting highly precise products and components. Hence, it is no surprise that it finds widespread applications in medical technology, research and development, architecture, aerospace, military, automotive, and even creative arts. It is also employed for drilling holes at compound angles.

Limitations: While the 5-axis CNC machine excels in terms of speed and accuracy, it is not without its challenges:

The CAD/CAM programming for 5-axis machines can be exceedingly complex, particularly when visualizing the spatial trajectory. Due to the relative rarity of 5-axis milling machines, acquiring and maintaining one constitutes a substantial investment, with equally expensive tooling solutions. Operating a 5-axis machine demands an exceptionally skilled CNC machine operator.

7-Axis CNC Machining

7-axis CNC milling machines have the capability to manufacture long, slender, and intricately detailed parts. The seven axes involved encompass the typical right-left, top-down, and back-front movements, along with the axes defined by the spinning of the tool, rotation of the part, rotation of the tool head, and movement for clamping, reclamping, or removing the part. These motions can be categorized as follows:

X-axis translationHorizontal movement from left to right
Y-axis translationVertical movement from bottom to top
Z-axis translationForward and backward movement along the depth
A-axis rotationRotation around the horizontal X-axis
B-axis rotationRotation around the vertical Y-axis
C-axis rotationRotation around the longitudinal Z-axis
E-axis rotationTwisting of the arm itself

This extensive range of movement contributes to enhanced precision in the final product without the necessity for additional post-fabrication processes. The 7-axis CNC machine’s capability to mill while simultaneously turning the part within the frame enables the production of exceptionally complex shapes and features. Such machines find particular utility in the aerospace and military industries.

9-Axis CNC Machining

The 9-axis CNC machining system integrates a 4-axis lathe with a 5-axis milling machine. Typically, this configuration incorporates a 5-axis CNC milling machine for surface machining and a 4-axis lathe for internal machining. This configuration endows 9-axis machines with all the rotations and translational movements, along with rotations around two additional axes referred to as the U and W axes.

Consequently, components can undergo turning and milling across various planes in a single setup with remarkable precision. One of the primary advantages of a 9-axis CNC system is the elimination of secondary fixtures and manual loading. The 9-axis CNC is so highly capable that it can produce a fully-finished product in a single fixturing. Common applications for 9-axis machines include implantable medical devices, intricate aerospace components, surgical tools, and dental implants.

12-Axis CNC Machining

If 9-axis CNC machining is the whole package, then its 12-axis counterpart is an absolute beast! The 12-axis CNC machines typically contain two heads that allow movement along the X, Y, Z, A, B, and C-axes. This configuration doubles productivity and accuracy while cutting down manufacturing time by half!

Final Thoughts on Types of CNC Machine Axes

CNC machining continues to stay relevant and effective to this day. It serves various manufacturing-intensive sectors and maintains product quality, precision, and standardization. As machines acquire more axes of movement, they are only bound to get better with each iteration. So while they may be a significant investment, they also promise long-lasting service in return!

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