Composite machining, as one of the development directions of machining, is also a major direction for the development of CNC equipment. In a variety of composite processing areas, turn-milling machining is currently one of the most developed areas. At various exhibitions at home and abroad, we can see that many machine tool manufacturers have launched such devices as the display content of high-end equipment.
The price of turning and milling compound processing equipment is often rather expensive. Many companies often look at such equipment as special machine tools when selecting equipment. However, they do not give equipment more scope of use. They are often based on the technology of a part. Demand to formulate equipment procurement plans. Before selecting equipment types, first consider whether the increase in single item costs due to equipment depreciation is within the allowable range, so as to decide whether to purchase such equipment. Many of the milling and milling complex processing equipment are In this situation was introduced. The reason for this phenomenon is that people do not know enough about the application of such equipment. Besides worrying about the cost of routine maintenance, the preparation of the processing program is confusing, so people are more willing to choose to purchase a 5-axis machining system. Center and a CNC car. In addition, in theory, turning and milling combined machining can effectively improve product quality and production efficiency, but in practical applications, it can not be satisfactory. The main factor is the preparation of machining programs.
Here we explore how to compile the machining program for turning-milling machining centers from two perspectives of how to increase the efficiency of equipment use and expand the application field.
First of all, let's take a look at how to improve the efficiency of the use of the double-turret turning and milling center. In the process of machining, multiple parts processing can be completed by synchronous operation of double tool holders. Because there are many kinds of processing procedures for the same workpiece, the use of computer-aided processing software to complete the part programming, can optimize the process, under the premise of processing conditions allow, try to make the two tool holders at the same time at work, no doubt can be effective Reduce processing time. Here are three examples. Through these three examples we can see the effect of processing.
The clearance can be removed more quickly by the simultaneous setting of the upper and lower blade holders. At the same time, the rough shape of the inner hole can be completed.
Through the simultaneous setting of the upper and lower tool holders, a series of holes can be processed, which not only improves the machining efficiency, but also reduces the influence of the workpiece deformation through the mutual cancellation of the axial forces of the drilling holes.
Two-stage machining can be completed at one time through the synchronized setting of the upper and lower blade holders.
The two-turret device has a dual-channel control system. The upper and lower tool holders can be individually controlled. Synchronization processing can be achieved through synchronization statements in the code. For example, in the following code, M10 and M15 are synchronization statements. The syntax of the synchronization statement is determined according to the requirements of the controller. The number of synchronization statements is determined based on the contents of the synchronization process. The content between the synchronization statements is the content of synchronous processing.
The optimization of the processing program can undoubtedly increase the production efficiency, especially for the high-volume parts processing. Imagine that if the processing time of each part can save 1 second, then it can be saved from tens of thousands of parts. The time and resources will be unthinkable.
Let's look at the application of turning and milling compound processing equipment. In addition to their application in high-volume processing of certain products, milling and milling machines are also very useful for small batches or single-piece production. Because it has the control ability of at least one rotation axis, to expand its application range, it can even replace the work of the multi-axis linkage machining center.
The following is the application of turning and milling equipment in the processing of impeller blades. As a typical part type for five-axis machining, blade machining has a huge market demand. In fact, most of these parts can be completed in the milling and milling center. For some milling and milling machines with B-axis linkage, the types of parts that can be machined will be more extensive. This kind of equipment not only has the turning function, but also can complete the milling work of three to five coordinate linkages. With the development of the machine hardware, the rigidity of the machine tool can be significantly improved, and the rough finish machining can be completed at one time, and from the craft point of view, Turning and milling compound equipment has the advantages of simple positioning of parts, various rough machining methods, and convenient chip removal. At the same time, the milling and milling equipment is closer in price to the multi-axis milling and machining center of the same grade. Therefore, it is becoming a reality that the machining of the impeller blades is completed on the turning and milling composite machine.
For ordinary C&Y turning and milling equipment, the machining of the blades can be accomplished through a C-axis linkage. This type of control system is actually a three-axis control system. Through the XZC three-axis linkage to complete the processing of the surface, without having to make more investment in the machine, you only need to select a CAM software that can provide this function. As shown in Figure 1:
figure 1
figure 2
image 3
For high-end turning and milling machines with B-axis capabilities, better surface quality can be achieved with B-axis angling or XYZBC five-axis machining (Fig. 2). At the same time, this type of equipment can also perform more complex impeller blade machining (Figure 3).
Most of the turning and milling machines have their own programming functions. For example, the Mazak matrix series and the HEIDENHAIN CNC PILOT 3190 series control systems all have interactive programming functions for human-machine dialogue. They can not only complete two-axis turning, but also complete C&Y auxiliary power. Head of conventional milling machining programming, but for some complex parts of the surface processing can not do anything. In this case, only CAM software can be used to achieve this. Therefore, for the turning and milling complex, especially the high-end turning and milling machining equipment with double turrets, it is necessary to play its due performance, and it is inseparable from the support of CAM software. However, in the application of CAM software, the formulation of post-processing is particularly important.
Due to the existence of the rotation angle coordinate, when programming in the CAM software, people are accustomed to use the absolute coordinate programming mode of the tool tip point. When the generated NC code runs on the machine tool, the control system needs to have the function of three-dimensional tool length compensation ( As shown in FIG. 4 , the control system automatically implements tool length compensation in three-dimensional space based on the actually used tool length L2. (Note: In fact, the control system calculates the compensation based on the value of L1+L2, and the value of L1 can be directly set in the machine system parameters after the machine is commissioned). If the control system does not have a three-dimensional tool length compensation function, it is necessary to measure the length of the tool on the tool setting tool in advance, and then specify the tool length parameter in the CAM software environment before generating the machining program. Actually generate the coordinate points in the NC code. It is the coordinates of the center of rotation. During the application of this kind of program, the tool with the specified length must be used. (At the end of the last century, when the control system did not have the three-dimensional tool length compensation function, this method was used to complete the preparation of the five-axis coordinate program. To facilitate the use of the tool, a retractable sleeve was usually added to the machine tool spindle. Parts to adjust the tool length to the programmed tool length).
Figure 4
Figure 5
Regardless of whether it is absolute coordinate programming or rotary center coordinate programming, for the turning and milling center, the B axis has a special processing mode as a linkage axis, ie, the B axis coordinate following function. We take the absolute coordinate programming of the tool nose point as an example to see if there are differences in the program of the B axis coordinate following function (the B axis coordinate following function can also use the rotation center coordinate program, which is not discussed here). The difference between B axis coordinate follow function and tool nose point absolute coordinate programming is the rotation of coordinate system (as shown in Fig. 5). If B axis coordinate follow function is used, Z axis always follows the current position of the tool, but it always points to the spindle. The axis direction, so that in the calculation of three-dimensional tool compensation, the amount of control system hardware to reduce the amount of correspondingly more, more calculations completed in the CAM software. Therefore, this model is beneficial to save the control system resources to meet the high requirements of the control system when machining complex parts and high-speed machining. The following is a comparison of a program that uses the B axis coordinate following function and a program that does not use this function:
It can be seen here that in the two modes, the rotation coordinates in the program are the same, but the linear coordinates are different, that is, the position of the tool tip point changes with respect to the value of the current coordinate system. The B-axis coordinate following function is normally switched by a pair of G-code instructions.
Viewpoints on improving the efficiency of turning and milling compound machining and the multi-axis linkage application of turning and milling are not discussed in more detail because of space restrictions. More and more practices in the field of turning and milling machining will give us more possibilities. The subject of thinking, but we found that in turning and milling complex machining, many milling and milling functions need CAM software environment to support, so for a high-end milling and milling equipment, CAM software is one of the essential tools.
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