What is the difference between three-axis, four-axis, and five-axis machining centers?

The function and advantages of the three-axis machining center:

The most effective machining surface of the vertical machining center (three-axis) is only the top surface of the workpiece, and the horizontal machining center can only complete the four-sided machining of the workpiece with the help of the rotary table. At present, high-end machining centers are developing in the direction of five-axis control, and the workpiece can be processed in one clamping. If equipped with a high-end CNC system with five-axis linkage, it can also perform high-precision machining on complex spatial surfaces.
What is four-axis simultaneous machining?
The so-called four-axis simultaneous machining generally adds a rotating axis, which is usually called the fourth axis. The general machine tool has only three axes, that is, the workpiece platform can move left and right (1 axis), front and rear (2 axis), and the spindle head (3 axis) is used for cutting workpieces. Rotating electric indexing head! In this way, bevel holes can be automatically indexed, and beveled edges can be milled, etc., without the loss of accuracy by secondary clamping.

Four-axis linkage machining features:
(1). The three-axis linkage machining machine cannot be processed or needs to be clamped too long
(2). Improve the accuracy, quality and efficiency of free-space surfaces
(3). The difference between four-axis and three-axis; four-axis difference and three-axis with one more rotation axis. The establishment of four-axis coordinates and the representation of the code:
Determination of Z-axis: the axis direction of the machine tool spindle or the vertical direction of the worktable for clamping the workpiece is the Z-axis. Determination of the X-axis: the horizontal plane parallel to the workpiece mounting surface or the direction perpendicular to the rotation axis of the workpiece in the horizontal plane is the X-axis. The direction away from the spindle axis is the positive direction.
The five-axis machining center is divided into a vertical five-axis machining center and a horizontal five-axis machining center. What are their characteristics?

Vertical five-axis machining center

There are two types of rotary axis of this type of machining center, one is the rotary axis of the table.

The worktable set on the bed can rotate around the X-axis, which is defined as the A-axis, and the A-axis generally has a working range of +30 degrees to -120 degrees. There is also a rotary table in the middle of the worktable, which rotates around the Z-axis at the position shown in the figure, which is defined as the C-axis, and the C-axis rotates 360 degrees. In this way, through the combination of the A axis and the C axis, the workpiece fixed on the table can be processed by the vertical spindle except the bottom surface, the other five surfaces. The minimum division value of A-axis and C-axis is generally 0.001 degrees, so that the workpiece can be subdivided into any angle, and inclined surfaces, inclined holes, etc. can be processed.

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

But in general, the worktable can not be designed too large, and the bearing capacity is also small, especially when the A-axis rotation is greater than or equal to 90 degrees, the workpiece cutting will bring a large load-bearing moment to the worktable.

The front end of the main shaft is a rotary head, which can revolve around the Z axis 360 degrees and become the C axis. The rotary head also has an A axis that can rotate around the X axis, generally more than ±90 degrees, to achieve the same function as above. The advantage of this setting method is that the spindle processing is very flexible, and the worktable can also be designed to be very large. The huge body of the passenger plane and the huge engine casing can be processed on this type of machining center.

Features of horizontal five-axis machining center

There are also two ways for the rotary axis of this type of machining center. One is that the horizontal spindle swings as a rotary axis, plus a rotary axis of the worktable to achieve five-axis linkage processing. This setting method is simple and flexible. If the spindle needs to be converted vertically and horizontally, the worktable can be simply configured as a three-axis machining center with vertical and horizontal conversion only by indexing and positioning. The vertical and horizontal conversion of the main shaft cooperates with the indexing of the worktable to realize the pentahedral processing of the workpiece, which reduces the manufacturing cost and is very practical. CNC axes can also be set on the worktable, with a minimum index value of 0.001 degrees, but without linkage, it becomes a four-axis machining center for vertical and horizontal conversion, adapting to different processing requirements, and the price is very competitive.
The other is the traditional rotary axis of the worktable. The A-axis of the worktable set on the bed generally has a working range of +20 degrees to -100 degrees. There is also a rotary table B-axis in the middle of the worktable, and the B-axis can rotate 360 ​​degrees in both directions. This horizontal five-axis machining center has better linkage characteristics than the first method, and is often used to process complex curved surfaces of large impellers. The rotary axis can also be equipped with circular grating feedback, and the indexing accuracy can reach several seconds. Of course, the structure of this rotary axis is more complicated and expensive.

Most of the machining centers can be designed to exchange double worktables. When one worktable runs in the processing area, the other worktable replaces the workpiece outside the processing area to prepare for the processing of the next workpiece. The time of the worktable exchange depends on the worktable. Size, from a few seconds to tens of seconds to complete.


Post time: Sep-24-2022