Multi-axis linkage technologies, especially five-axis machining centers have become increasingly mature. Machining centers are more and more widely used in various fields of the machinery manufacturing industry, and many manufacturers have a demand for machining centers.

Three-Axis Machining Center

The three-axis machining center is the most widely used, including the X, Y, and Z axes, also known as three-axis simultaneous machining centers. The three-axis machining center can perform simple plane machining, but it can only machine one side at a time. It can effectively machine materials such as metal, aluminum, wood, etc.

Functions and Advantages of Three-Axis Machining Centers

The most effective machining surface of a vertical machining center (three-axis) is the top surface of the workpiece. A horizontal machining center, with the aid of a rotating table, can only complete the machining of the four sides of the workpiece. Currently, high-end machining centers are developing towards five-axis control, allowing the completion of five-sided machining in one setup. With the configuration of a high-end five-axis simultaneous CNC system, high-precision machining of complex spatial surfaces can also be achieved.

Four-Axis Machining Center

The four-axis machining center adds an additional rotation axis to the three-axis, usually the A-axis. The rotation of the A-axis allows the workpiece to rotate around the vertical axis on the horizontal plane, enabling multi-face machining. The four-axis machining center is suitable for situations where machining is required on different faces of the workpiece, such as inclined surfaces, oblique holes, etc.

Features of Four-Axis Simultaneous Machining

(1) Machining that cannot be achieved by three-axis simultaneous machining machines or requires overly complex fixturing.

(2) Improvement of the precision, quality, and efficiency of free-form surfaces.

(3) The difference between four-axis and three-axis is the addition of one rotation axis. The establishment of the four-axis coordinates and their code representation:

Determination of the Z-axis: The direction of the machine spindle axis or the vertical direction of the workpiece fixture is the Z-axis.

Determination of the X-axis: The horizontal plane parallel to the workpiece mounting surface or the direction perpendicular to the workpiece’s rotation axis within the horizontal plane is the X-axis, with the direction away from the spindle axis being the positive direction.

 

Five-Axis Machining Center

The five-axis machining center adds another rotation axis to the four-axis, usually the C-axis. The rotation of the C-axis allows the workpiece to rotate around an axis perpendicular to the table, enabling more complex multi-angle and surface machining. The five-axis machining center is suitable for complex shapes, multi-angle machining, including spatial surface machining, special-shaped machining, hollowing-out machining, drilling, oblique holes, oblique cutting, etc. It is a means to solve the machining of impellers, blades, ship propellers, heavy-duty generator rotors, steam turbine rotors, large diesel engine crankshafts, etc.

What are the 5 axis? in a five-axis machining center?

X-axis: The X-axis is the horizontal axis of the machining center, controlling the movement of the tool in the horizontal direction. The movement of the X-axis affects the lateral position of the workpiece, determining its position and shape on the horizontal plane.

Y-axis: The Y-axis is the longitudinal axis of the machining center, controlling the movement of the tool in the longitudinal direction. The movement of the Y-axis affects the longitudinal position of the workpiece, determining its position and shape on the longitudinal plane.

Z-axis: The Z-axis is the vertical axis of the machining center, controlling the movement of the tool in the vertical direction. The movement of the Z-axis affects the height position of the workpiece, determining its position and shape on the vertical plane.

A-axis: The A-axis is the rotation axis of the four-axis and five-axis machining centers, controlling the rotation of the workpiece on the horizontal plane. The rotation of the A-axis allows the workpiece to rotate around the vertical axis on the horizontal plane, enabling multi-face machining.

C-axis: The C-axis is the rotation axis of the five-axis machining center, controlling the rotation of the workpiece around an axis perpendicular to the table. The rotation of the C-axis allows the workpiece to rotate around the rotation axis on the vertical plane, enabling more complex multi-angle and surface machining.

Types of Five-Axis Machining Centers

Vertical Five-Axis Machining Center

This type of machining center has two methods for the rotation axis: one is the worktable rotation axis.

The worktable, which is set on the bed, can rotate around the X-axis, defined as the A-axis. The general working range of the A-axis is +30 degrees to -120 degrees. There is also a rotating table in the middle of the worktable, which rotates around the Z-axis at the position shown in the illustration, defined as the C-axis. The C-axis can rotate 360 degrees. With the combination of the A-axis and C-axis, the workpiece fixed on the worktable can be machined on all five sides except the bottom surface by the vertical spindle. The minimum indexing value for the A-axis and C-axis is usually 0.001 degrees, which allows the workpiece to be subdivided into any angle for machining inclined surfaces and oblique holes.

If the A-axis and C-axis are linked with the XYZ three linear axes, complex spatial surfaces can be machined. Of course, this requires the support of high-end CNC systems, servo systems, and software. The advantage of this setup is that the structure of the spindle is relatively simple, the spindle rigidity is very good, and the manufacturing cost is relatively low.

Spindle Rotation Vertical Five-Axis Machining Center

The vertical machining center’s spindle has gravity acting downward, and the radial force on the bearings during high-speed idle operation is equal, resulting in good rotation characteristics. Therefore, the speed can be increased, with a general high speed reaching over 12,000 rpm, and the practical maximum speed has reached 40,000 rpm. The spindle system is equipped with a circulating cooling device, where the circulating cooling oil carries away the heat generated by high-speed rotation, is cooled to an appropriate temperature through a chiller, and then flows back into the spindle system.

The X, Y, Z three linear axes can also use linear encoders for feedback, with bidirectional positioning accuracy within the micron level. Since the rapid feed reaches 40-60 m/min or more, the ball screws for the X, Y, Z axes mostly adopt central cooling. Similar to the spindle system, the heat is carried away by the circulating oil that flows through the center of the ball screws after being chilled.

 

Zusammenfassung

In the field of CNC machine tools, three-axis machining centers have relatively simple processing capabilities, four-axis machining centers can achieve multi-face machining, and five-axis machining centers have a higher level of multi-angle and surface machining capabilities. The main difference between three-axis, four-axis, and five-axis machining centers lies in the number of axes and processing capabilities. The choice of a suitable machining center should be determined based on specific processing requirements and complexity.