The most effective processing surface of the machining center (three axes) is the top surface of the workpiece. With the help of the rotary table, the horizontal machining center can only process the workpiece on four sides. The current machining center is developing in the direction of five-axis control. The pentahedron can be processed in one clamping. If a high-end CNC system with five-axis linkage is configured, high-precision machining of complex space surfaces can also be completed.
Schematic drawing of mold engraving of five-axis machining center
1. Vertical five-axis machining center
There are two ways for the rotary axis of this type of machining center. One is the rotary axis of the table, which is good at subdividing the workpiece into any angle and processing inclined surfaces and inclined holes. With the support of high-end CNC system, servo system and software, complex space surfaces can be processed. The advantage is that the structure of the main shaft is relatively simple, the rigidity is also very good, and the manufacturing cost is low. But the workbench can’t be designed too big, and the load is relatively small.
The other is to rely on the rotation of the vertical spindle head.The front end of the spindle is a rotary head.The advantage of this setting method is that the spindle processing is very flexible, and the worktable can also be designed very large.The huge engine and the huge body of the shell passenger aircraft Etc. can be processed on this type of processing center.
This type of design also has a big advantage: when using a spherical milling cutter to process a curved surface, when the center line of the tool is perpendicular to the machining surface, because the linear velocity of the vertex of the spherical milling cutter is zero, the quality of the workpiece surface cut by the vertex will be very Poor, the spindle is rotated, the spindle is rotated through an angle relative to the workpiece, so that the spherical milling cutter avoids the apex cutting, and a certain linear speed is guaranteed, which can improve the surface processing quality. This structure is very popular with high-precision surface machining of molds, which is difficult to achieve with the rotary machining center of the worktable. In order to achieve high-precision rotation, the high-end rotary shaft is also equipped with circular scale feedback, and the indexing accuracy is within a few seconds. Of course, the rotary structure of this type of spindle is more complicated and the manufacturing cost is higher.
The spindle of the vertical machining center has downward gravity, and the radial force of the bearing is idling at high speed.The rotation characteristics are very good, so the speed can be increased.Generally, the high speed can reach more than 1,2000r / min, and the practical maximum speed has been reached. 4,0000 rpm. The main shaft system is equipped with a circulating cooling device. The circulating cooling oil takes away the heat generated by the high-speed rotation, drops to the appropriate temperature through the refrigerator, and then flows back to the main shaft system.
2. Horizontal five-axis machining center
The rotary axis of this type of machining center is also divided into two forms, one is the horizontal spindle swing action is a rotary axis, plus a rotary axis of the table, to achieve five-axis linkage processing. This method is flexible and simple. The table only needs to be indexed and positioned, and it can be easily configured as a vertical and horizontal three-axis machining center to realize pentahedron machining of the workpiece. The manufacturing cost is low and it is very practical. You can also set a CNC axis on the worktable, the minimum index value is 0.001 degrees, but without linkage, it becomes a four-axis machining center for vertical and horizontal conversion, adapting to different processing requirements for conversion, and the price is very competitive.
The other is the traditional rotary table of the worktable, its linkage characteristics are better than the first method, and it is widely used in the processing of complex curved surfaces of large impellers. The rotary axis can also be configured with feedback from a circular grating ruler, and the indexing accuracy can reach several seconds. The rotary axis structure is relatively complicated and the price is relatively high.
At present, the table of horizontal machining center can be larger than 1.25m2, which has no effect on the first five-axis setting method. But the second five-axis setting method is more difficult. The spindle speed of the horizontal machining center generally reaches more than 10,000rpm.Because the spindle set in the horizontal type has self-gravity in the radial direction, the radial force is uneven during high-speed idling of the bearing.In addition, a larger BT50 tool holder is required, the highest Up to 20,000rpm. The rapid feed of the horizontal machining center reaches more than 30 ~ 60m / min, the spindle motor power is more than 22-40KW, the tool magazine capacity can be increased from 40 to 160 as needed, and the processing capacity is far more than the general vertical machining center, which is heavy First choice for machining.
Most of the machining centers can be designed as double-table exchange, one worktable runs in the processing area, and the other worktable is used to replace the workpiece outside the processing area to prepare for the next workpiece. The exchange time is based on the size of the worktable. It can be completed in seconds to tens of seconds.
The future development of machining centers is limitless. In the past, five-axis machining centers were mostly made in Germany, Italy, the United States, and Japan. However, domestically-produced five-axis machining centers are also widely used today. This indicates that China’s CNC machine tool industry has reached an advanced level. Now the processing center has gradually become the most important equipment in the mechanical processing industry. It has a wide processing range and a large amount of use.
In recent years, great progress has also been made in terms of variety, performance, and functions. A new type of vertical and horizontal five-axis machining center can be used for aerospace and aerospace parts processing; a high-performance machining center dedicated to mold processing, integrated 3D CAD / CAM for super-precision machining of complex curved surfaces of molds; also suitable for motorcycles, The high-speed machining center for processing large quantities of automotive parts has high production efficiency and flexibility. The current equipment will exchange information with the outside world through the network to obtain the latest technological achievements, and human wisdom will be fully demonstrated in the high-tech product processing center.