Technology and tooling of the hottest machining ce

Process and tooling of machining center

machining center is a CNC machining machine with a wide range of processes, which can carry out milling, boring, drilling, thread processing and other work. The machining center is especially suitable for machining box parts and hole systems. The range of processing technology is shown in figure 1-figure 4

Figure 4 boring processing

1 Technological analysis

generally, the following aspects are mainly considered: (1) select the processing content

machining centers are most suitable for machining parts with complex shapes, many processes and high requirements, which require the use of various types of general-purpose machine tools, cutters and fixtures, which can only be completed after multiple clamping and adjustment. (2) Check the part drawing

the part drawing should be correctly expressed and marked. At the same time, special attention should be paid to the unified design basis as far as possible in the drawing, so as to simplify programming and ensure the accuracy requirements of parts

for example, the part drawing shown in Figure 5. In Figure 5a, both sides a and B have been processed in the previous process, and only all holes are processed on the machining center. When positioning on both sides a and B, there is no unified design basis for the height direction, ф 48h7 hole and two above ф The size of hole 25h7 and side B is indirectly guaranteed. To ensure the size of 32.5 0.1 and 52.5 0.04, the size tolerance of 105 0.1 must be compressed in the previous process. If it is changed to the marked size shown in Figure 5b, the position and size of each hole are based on plane a, the datum is unified, and the process datum coincides with the design datum, so it is easy to ensure the passenger car speed increase and the standard modification inch of the spring of the railway system. (3) Analyze the technical requirements of parts

analyze whether the geometric accuracy and technical requirements are reasonable according to the functions of parts in the product; Consider whether the accuracy and technical requirements can be guaranteed when processing in the machining center; Which machining center is the most reasonable choice. (4) Check whether the structural manufacturability of the manipulation should be paid attention to when the parts are clamped and loaded.

analyze whether the structural rigidity of the parts is sufficient, and whether the structural manufacturability of each processing part is reasonable, etc

2. Process design

in process design, accuracy and efficiency are mainly considered. Generally, the principle of "first surface then hole", "first benchmark then others", and "first coarse then fine" is followed. The machining center shall finish all the machining of the surface that can be machined as far as possible in one clamping. For the hole system processing with high position accuracy requirements, special attention should be paid to arranging the processing sequence of holes. Improper arrangement may bring in the reverse clearance of the transmission pair and directly affect the position accuracy. For example, when arranging the hole series processing sequence of the customer's photographic parts of the product during the zero period shown in Figure 6a, if the processing is carried out according to the route shown in Figure 6B, due to 5 The positioning direction of hole 6 is opposite to that of hole 1.2.3.4 in the Y direction, and the reverse clearance in the Y direction will increase the error, thus affecting the position accuracy of hole 5.6 and other holes. According to the route shown in Figure 6C, the introduction of reverse clearance can be avoided

Figure 6 training line for professional talents in boring processing road

in the processing process, in order to reduce the number of tool changes, a centralized tool process can be adopted, that is, use the same tool to process the corresponding parts on the part, and then change the second tool to continue processing. However, for the hole system with high accuracy requirements, if the parts are determined by the rotation of the workbench, this method cannot be adopted because of repeated positioning errors. 3. Clamping of parts

(1) selection of positioning datum

when machining in the machining center, the positioning of parts should still follow the six point positioning principle. At the same time, special attention should also be paid to the following points:

1) when carrying out multi station processing, the selection of positioning reference should consider the positioning method that can complete as many processing contents as possible, even if all surfaces can be processed. For example, for box parts, the combined positioning method of one side and two pins should be adopted as far as possible

2) when the positioning datum and design datum of a part are difficult to coincide, the assembly drawing should be carefully analyzed to clarify the design function of the design datum of the part. Through the calculation of the dimension chain, the dimensional position accuracy requirements between the positioning datum and design datum should be strictly stipulated to ensure the machining accuracy

3) the programming origin and the part positioning datum may not coincide, but there must be a definite geometric relationship between them. The selection of programming origin mainly considers the convenience of programming and measurement. For example, the part in Figure 7 processes 80h7 holes and 4- 25h7 holes on the machining center, of which 4- ф 25h7 all in ф 80h7 hole is the benchmark, and the programming origin should be selected at ф Center line of 80h7 hole. When the positioning datum of the part is on both sides a and B, the positioning datum does not coincide with the programmed origin, but it can also ensure the machining accuracy

Figure 7 Programming origin and positioning reference

(2) clamping of parts

when considering the clamping scheme, it is necessary to ensure reliable clamping and minimize clamping deformation. (3) Selection of fixture

on the machining center, the task of the fixture is not only to clamp the parts, but also to determine the machining origin of the parts with the positioning datum as the reference datum. Therefore, the positioning datum should be accurate and reliable

4. Selection of cutting tools

the basic requirements of machining centers for cutting tools are:

1) good cutting performance: it can withstand high-speed cutting and strong cutting and has stable performance

2) higher accuracy: the accuracy of the tool refers to the shape accuracy of the tool and the position accuracy of the tool and the clamping device

3) equipped with perfect tool system: meet the requirements of Multi Tool continuous processing

the cutter head part of the cutter used in the machining center is basically the same as that used in the NC milling machine. About the selection of NC milling cutter. The tool handle part of the tool used in the machining center is different from that of the general NC milling machine. The tool handle used in the machining center has a clamping groove for the manipulator to clamp