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Programming Difference between Three-axis and Five-axis Machining Centers

Source:Shenzhen Xinya Precision Hardware Products Co., Ltd. Published date:2018-01-20 21:18:44

Five-axis machining center workpiece can be clamped once to complete the pentahedron processing, but also to complex space surface for high-precision processing. The most effective processing surface of vertical machining center (three axes) is only the top surface of the workpiece. Horizontal machining center can only complete the four-sided processing of the workpiece with the help of rotary table.


  I. Vertical Five-Axis Machining Center


 Ⅰ. Workbench Rotary Shaft

The worktable set on the bed can revolve around the X axis, which is defined as the A axis. The A axis generally has a working range of + 30 degrees to - 120 degrees. There is also a turntable in the middle of the worktable, which revolves around the Z axis in the position shown. It is defined as the C axis, and the C axis is 360 degrees revolving. In this way, through the combination of A axis and C axis, the workpiece fixed on the worktable can be processed by the vertical spindle except the bottom. The minimum indexing value of axes A and C is generally 0.001 degrees, so that the workpiece can be subdivided into arbitrary angles and the inclined surface and hole can be machined. If Axis A and C are linked with XYZ three linear axes, complex space surface can be machined. Of course, this requires the support of high-grade CNC system, servo system and software. The advantages of this method 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 the general worktable can not be designed too large, and the load-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 great bearing moment to the worktable.


2. Relying on the Rotation of Vertical Spindle Head

The front end of the spindle is a revolving head, which can revolve 360 degrees around the Z axis and become the C axis. The revolving head is also equipped with an A axis which can revolve around the X axis. Generally, the revolving head can reach more than 90 degrees, which achieves the same function mentioned above. The advantage of this method is that the spindle processing is very flexible, the worktable can also be designed very large, the huge airplane body, the huge engine shell can be processed in such processing centers. This design also has one big advantage: when we use spherical milling cutter to process surface, when the center line of the cutter is perpendicular to the machining surface, because the vertex linear velocity of the spherical milling cutter is zero, the surface quality of the workpiece cut by the vertex will be very poor. The design of spindle rotation makes the spindle rotate an angle relative to the workpiece, so that the spherical milling cutter avoids the vertex cutting and ensures a certain linear speed. It can improve the quality of surface processing. This kind of structure is very popular in high precision surface processing of dies and dies, which is difficult for rotary machining centers of worktables. In order to achieve high accuracy of rotation, the high-grade rotary shaft is equipped with grating ruler feedback, and the accuracy of indexing is within a few seconds. Of course, the rotation structure of this kind of spindle is more complex and the manufacturing cost is higher.

The spindle gravity of the vertical five-axis machining center with spindle rotation is downward, the radial force of the bearing is equal in high-speed air operation, and the rotation characteristic is very good. Therefore, the rotational speed can be increased. Generally, the high speed can reach more than 1,2000 r/min, and the practical maximum speed has reached 4,000 rotational speed. The spindle system is equipped with a circulating cooling device. The circulating cooling oil takes away the heat generated by high-speed rotation, drops to the appropriate temperature through the cooler, and then flows back to the spindle system. X, Y and Z three linear axes can also be fed back by linear grating ruler, and the two-way positioning accuracy is within the micron level. Because of the fast feeding up to 40-60 m/min, X, Y and Z axis ball screw mostly adopts central cooling. Like the spindle system, the refrigerated circulating oil flows through the center of the ball screw and takes away heat.
Ⅱ. Horizontal Five-Axis Machining Center
1. Horizontal spindle swing action as a rotary axis, coupled with 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 transformed from vertical to horizontal, the worktable can be simply configured as a three-axis machining center with vertical and horizontal transformations only by indexing and positioning. With the main shaft vertical and horizontal conversion and the worktable indexing, pentahedron processing is realized for the workpiece, which reduces the manufacturing cost and is very practical. NC axis can also be set on the worktable, the minimum indexing value is 0.001 degrees, but without linkage, to become a vertical and horizontal conversion of the four-axis processing center, to meet different processing requirements, the price is very competitive.
2. The traditional rotary axis of the worktable. The working range of the A-axis of the worktable set on the bed is from + 20 degrees to - 100 degrees.
The center of the worktable is also provided with a rotary table B axis, which can rotate 360 degrees in both directions. The linkage characteristic of this horizontal five-axis machining center is better than that of the first one. It is often used to process complex surface of large impeller. Rotary axis can also be equipped with circular grating ruler feedback, the accuracy of indexing can reach several seconds, of course, the structure of the rotary axis is more complex, and the price is expensive.

The spindle speed of horizontal machining center is generally over 10,000 rpm. Because of the self-gravity of the horizontal spindle in the radial direction, the radial force of bearings is uneven in high-speed air running. In addition, the larger BT50 tool holder is used, which can generally reach up to 20,000 rpm. Horizontal Machining Center has a fast feed rate of 30-60 m/min, a spindle motor power of 22-40 KW or more, and a tool library capacity of 160 can be increased from 40 to 160 as required. Its processing capacity is far beyond that of general vertical Machining Center. It is the first choice for heavy machinery processing.

    【Article Tags】:Rotary Machining Center General
    【Responsible editor】:Shenzhen Xinya Precision Hardware Products Co., Ltd.Copyright:Reprinted please indicate the source