Curious about the Composition, Structure, and Functions of a 5-Axis CNC Machining Center?

The Functions of a 5-Axis Machining Center

A 5-axis CNC machine tool is a high-tech and high-precision equipment designed specifically for processing complex surfaces. This type of machine tool system plays a crucial role in industries such as aerospace, military, scientific research, precision instruments, and high-precision medical equipment within a country.

Nowadays, it is widely acknowledged that the 5-axis CNC machine tool system is the sole means to address the processing of components like impellers, blades, ship propellers, heavy-duty generator rotors, turbine rotors, large diesel engine crankshafts, and more.

The 5-axis machining center is not only applied in civilian industries such as wood mold manufacturing, bathroom trimming, automotive interior part processing, foam mold processing, European-style home furnishings, solid wood chairs, etc., but it is also extensively utilized in aerospace, military, scientific research, precision instruments, high-precision medical equipment, and other industries.

The 5-axis machining center is a high-tech tool that transforms the impossible into the possible, allowing the machining of any spatial surface and irregular shapes. It not only accomplishes the mechanized processing of complex workpieces but also rapidly enhances processing efficiency and shortens the processing workflow.

The Structure of a 5-Axis CNC Machining Center

Most 5-axis machining centers adopt a 3+2 structure, meaning they consist of three linear motion axes (X, Y, Z) and two rotational axes (A, B, or A, C), with rotations around the X, Y, or Z axes. Broadly classified, there are three main configurations: X, Y, Z, A, B; X, Y, Z, A, C; and X, Y, Z, B, C. Further categorizing based on the combination of two rotational axes, there are generally three forms: dual rotary table, rotary table with swing head, and dual swing head.

1. Five-axis CNC Machine With Dual Rotary Tables

These three structural forms, due to physical constraints, determine the size specifications of the machine tool and the range of objects it can process. Among them, the dual rotary table structure of the 5-axis machining center is suitable for processing small parts, such as small integral turbines, impellers, and small precision molds. Since the structure is simpler, it is relatively more affordable. In terms of application, this type represents the most common category of 5-axis CNC machine tools.

2. Five-Axis CNC Machine With a Rotary Table and Swing Head Structure

A 5-axis machining center with a rotary table and swing head structure can have various combinations as the rotary table can be along the A, B, or C axis, and similarly, the swing head can be along the A, B, or C axis. This flexibility allows the machine to adapt to different processing needs.

For example, when machining the blades of a steam turbine generator, the A and B axes are required, with the A axis supported by a tailstock tip to hold the workpiece. If the workpiece is long and slender, it needs to be clamped at both ends and stretched during processing. Strict synchronization of the two rotary tables is necessary.

Another example is shown in Figure 2, where the C axis is combined with the B axis for machining. Since the workpiece only rotates on the C axis, it can be of varying sizes, ranging from small to large with diameters ranging from tens of millimeters to several thousand millimeters. The diameter of the C-axis rotary table can also vary from 100-200 mm to 2-3 m. The specifications and quality of the machine range from a few tons to tens of tons.

This type of 5-axis CNC machine tool is widely used, with a moderate price point. The price varies significantly depending on the machine's specifications, size, accuracy, and performance. The structure of a 5-axis machining center with dual swing heads, as shown in Figure 3, is inherently larger due to the presence of a spindle with a retractable knife structure in the middle of the swing head. Generally, the size of the dual swing heads is not easily reduced and is typically in the range of 400-500 mm.

3. Five-Axis CNC Machine With Dual Swing Heads

In the early stages, dual swing heads typically adopted adjustable-gap worm gear structures or backlash-eliminating gear structures. The machine's performance (rigidity and precision) was often determined by the rigidity of the dual swing head transmission chain.

Specifically, the clearance of the transmission gears was designed to be negative, and the gears operated within a certain elastic deformation state, the magnitude of which depended on the preloading force in that transmission segment. Figure 3(a) illustrates a Spanish-style dual swing milling head employing gear transmission and a mouse tooth disc positioning structure. Its rigidity surpasses that of typical dual swing milling heads, making it particularly suitable for efficient machining of five-sided surfaces.

In more recent 5-axis machining centers, the structure of the rotary axis commonly incorporates torque motors utilizing the so-called "zero drive" technology, such as renowned brands like Mikron from Switzerland and DMG Mori from Germany. The application of zero-drive technology in the rotary axis is perhaps the most ideal technological solution for addressing the rigidity and precision of its transmission chain.

With the development of technology, the manufacturing cost of torque motors has significantly decreased, leading to a decline in market prices. This trend is expected to propel the manufacturing technology of 5-axis machining centers to a higher level.