Analyze the common functions of the four machining centers:
(1) Vertical machining center
The spindle of the vertical machining center is in a vertical position. It performs milling, boring, drilling, tapping and thread cutting. The vertical machining center is at least three-axis and two-linkage, and generally can realize three-axis three-linkage. Some can carry out five-axis and six-axis control, and the process personnel can determine the processing range of the machining center according to the number of axes that they control at the same time.
The height of the vertical machining center column is limited. When determining the range of motion of the Z axis, consider:
1 the height of the workpiece;
2 fixture height;
3 the length of the tool;
4 The space occupied by the robot to change the knife.
After considering the above four cases, the vertical machining center has to reduce the processing range of the box-type workpiece, which is the weakness of the vertical machining center. However, vertical machining centers have the following advantages:
1 The workpiece is easy to be clamped, and the workpiece can be clamped by universal clamps such as flat jaws, pressure plate, indexing head, rotary table, etc., and the workpiece is conveniently positioned and positioned;
2 The tool movement track is easy to observe, the debugging program is easy to check and measure, and the problem can be found in time, and the machine can be stopped or modified.
3 cooling conditions are easy to establish, the coolant can directly reach the tool and the processing surface;
The coordinate axes of the four coordinate systems X, Y and Z are consistent with the Cartesian coordinate system, and the sense is intuitive and consistent with the drawing angle;
5 chips are easy to remove and fall, avoiding swarf scratching the processed surface;
The structure of 6 is generally a single column type, which has a simple structure, a small floor space and a low price compared with the corresponding horizontal machining center.
The vertical machining center (Fig. 5-1) is most suitable for machining workpieces with relatively small dimensions in the Z-axis direction. In general, except for the bottom surface, the other five surfaces can be contoured and surface-finished with different tools.
(2) Horizontal machining center
The spindle of the horizontal machining center is horizontally set. The general horizontal machining center has three to five coordinate axes, often equipped with a rotary axis (or rotary workpiece table), the spindle speed is within 10 ~ 10000r / min, the minimum resolution is generally lμm, the positioning accuracy is 10μm - 20 μm. The horizontal machining center has a large magazine capacity, and some magazines can store hundreds of tools. The structure of the horizontal machining center is more complicated than the vertical machining center, and the volume and area are large, and the price is also high. Horizontal machining centers are more suitable for machining box parts. As long as the clamp is placed on the rotary table, the four faces of the case (except the top and bottom faces) can be milled, boring, drilling, tapping and the like. In particular, there are position tolerances for some holes and cavities on the box parts (such as the parallelism between the holes, the perpendicularity of the holes and the end faces, the perpendicularity of the end faces and the bottom surface, etc.), as well as the holes and cavities. With the strict dimensional accuracy requirements of the reference surface (bottom surface), it can be easily ensured by one-time clamping processing on the horizontal machining center, which is suitable for the processing of batch workpieces. When the horizontal machining center program is debugged, it is not as intuitive and easy to observe as the vertical machining center. It is inconvenient for the inspection and measurement of the workpiece, and the debugging time of the machining program for complex parts is several times that of normal machining, so the number of workpieces processed is more. The average time that each piece occupies the machine tool is less, so it is cost-effective to use a horizontal machining center for batch processing. However, it can achieve the precision and quality requirements that are difficult to achieve in common equipment. Therefore, some workpieces with high precision requirements and other equipment cannot meet their accuracy requirements, especially those with space surfaces and complex shapes, even for single-piece production. Processing on a horizontal machining center. It can be seen that the machining center is an efficient and high-quality automated production equipment, and it is also a device to overcome the technical problems.
The coordinate system of the horizontal machining center and the coordinate system of the vertical machining center, that is, the X, Y, and Z axes are spatially different. Moreover, the cooling conditions of the horizontal machining center are not as good as those of the vertical type, especially for the deep hole boring, milling, drilling, etc., the coolant is difficult to reach the depth of the cutting, therefore, the speed and feed rate of the machine tool must be reduced, and the production efficiency is reduced. . Compared with the vertical machining center, the horizontal machining center has many functions, and the workpieces that cannot be processed on the vertical machining center can be processed generally in the horizontal machining center. In addition, the rotary table of the horizontal machining center is numerically controlled, and some are indexed. The workpiece can be processed in multiple positions by one clamping. In general, horizontal machining centers have their advantages and disadvantages, and they are used to avoid them.
(3) Multi-table machining center
Multi-table machining centers are sometimes referred to as flexible machining units (FMC). The utility model has two or more replaceable worktables, and the processed workpiece can be removed from the processing part together with the worktable (tray) by the transport rail, and then the worktable (tray) containing the workpiece to be processed is sent to the processing part. Multiple exchangeable workbenches can be set up for multi-stage machining. The utility model has the advantages that the online clamping can be realized, that is, while the processing is being performed, the lower working table is loaded and unloaded, and the workpiece to be processed can be installed on other working tables, and after the machine is started, the work can be completed. The automatic machining of batch workpieces, the workpieces on the workbench can be the same or different. This can be handled by the program. Multi-table machining centers are available in both vertical and horizontal. Whether it is vertical or horizontal, its structure is more complicated, the tool magazine has a large capacity, the machine tool covers a large area, and the control system functions more comprehensively. The calculation speed is fast and the memory capacity is large. The most advanced CNC system is used, so it is expensive.
(4) Composite machining center
The composite machining center is also called the multi-face machining center, which refers to the equipment that can complete the machining of multiple faces after the workpiece is clamped once. The existing five-face machining center can complete the processing of five faces except the installation bottom surface after the workpiece is clamped once. This machining center combines the functions of a vertical and horizontal machining center to ensure the positional tolerance of the workpiece during machining. The common five-face machining center has two forms, one is the spindle or the corresponding angle rotation, which can be a vertical machining center or a horizontal machining center. The other is that the table rotates with the workpiece, and the spindle does not change direction to achieve five-sided machining. No matter which kind of five-face machining center, there are disadvantages of complicated structure and expensive construction.
The function of the five-face machining center is more than that of the multi-stage machining center. The control system is advanced, and its price is about twice that of the multi-station machining center with the same working table size.
