1.Introduction
CNC punching shear composite machine tool is widely used in sheet metal parts machining process because of its high accuracy, high efficiency and low comprehensive cost. At present, the blanking process of sheet metal parts is developing towards diversification. CNC punching shear composite machine tool is the representative of this trend. The use of CNC punching shear composite machine tool is different from other machine tools. It is necessary to constantly sum up experience and skills in the process of production and application. This paper will introduce the application of CNC punching shear compound machine in sheet metal processing from various angles.
2. TheApplication of CNC Punching and Shear Composite Machine Tool
Because the CNC punching shear composite machine tool is a kind of integrated CNC processing equipment, the complete process flow must be considered in the application, which should include the operation process of the punching machine, the shearing machine and the cooperative application of the two.
2.1Lofting
Sheet metal lofting is to draw a physical object or a three-dimensional drawing into a plan, so that it can be cut and processed. Lofting is generally divided into two types: manual lofting and Computer Lofting. Manual lofting mainly includes drawing method, calculation method, coefficient method and so on. These methods are widely used in practical engineering, and generally, the operators are required to master them. But the errors of manual lofting can be large, it is inefficient and the processing accuracy is quite low. Therefore, at present, many enterprises should adopt computer software for accurate lofting, and their work efficiency and processing quality have been greatly improved. There are many lofting software, such as AutoPOLforWindows, FastSHAPES, Jinlin sheet metal lofting software, etc.
2.2 Layout
The so-called layout is to find the optimal distribution of the processed parts on a piece of woolen material that is to be processed so that the material consumption can be minimized and the parts cannot overlap each other. CNC punching shear composite machine tools are equipped with feeding and unloading material subsystem, feeding and unloading materials are more convenient, but before processing, we must first layout according to the production plan. Because the general processing object of the CNC punching shear composite machine tool is mostly mass production, if there is no scientific and reasonable layout, the interests of the processing unit cannot be guaranteed. The principle of solving the layout problem of parts is to save plates and facilitate the processing of equipment. The layout of parts can be done manually or by computer programming, as shown in Figure 1. Computer layout is more efficient, so production enterprises usually use computer software to layout. How to further improve the utilization efficiency of sheet metal and introduce more advanced layout software is a subject that many scientific research institutes are studying. Many advanced control algorithms have been applied in the calculation of parts layout software, such as genetic algorithm, neural network, geometric optimization and so on. Thus, the layout of arbitrary shape parts can be solved, and the utilization ratio of plates can be improved.
2.3Programming
Before the CNC punching shear composite machine tool processing, first of all, the control personnel are required to write programs according to the requirements of the processing objects. The quality of processing programs is directly related to the quality of sheet metal parts. Therefore, a stable, reliable and streamlined control program is essential. The processing program can be automatically generated by computer software or manually written by the machine operators. In fact, automatically generated software is easy to operate because it does not require manual participation. However, automatic programming is rather rigid and inflexible, and the program code is chaotic, which brings difficulties to reading and modifying. Therefore, for the programming of complex parts, the programmers can modify the code of automatic programming, and add some instructions to optimize the program to make the generated software simple and reliable. For example, the M98 instruction. This instruction is a common subroutine call instruction for a CNC machine tool, which is suitable for the production and processing of massive workpieces. The general programmers will also consider using this instruction when the parts needed to be processed are small and complex. Next, take M98 as an example, briefly introduce the generation and the operation steps of the instruction.
The programming of CNC software is generally divided into two steps. One is CAD drawing, mainly drawing the processing objects; the other is CAM programming aided design, this process is to mainly complete the mold path and punching point, configure relevant information in software, and finally generate executable NC code program. After completing the automatic generation, the program can be manually modified. M98 instructions can be added to the program according to the situation.
M98 has a great advantage in simplifying the program. For example, it is often necessary to process many of the same slots or holes in processing sheet metal workpiece. In this way, we can first write a subprogram for punching shear slot or hole and then use the M98 to call the subprogram in the main program. Thus punching the same slots or holes in different locations. The main program is as follows:
In the process of punching and shearing compound control programming, M98 can be used to optimize programs and improve programming efficiency. Therefore, operators should be good at utilizing these similar instruction programs.
The processing procedure of sheet metal parts of CNC shear composite machine tool is different from the traditional process of sheet metal parts.
(1) Traditional processing technology. The traditional processing technology is divided into two steps. lofting first, processing second; punching and cutting. The first step is to use the shearing machine to loft the sheet according to the shape of the parts. In this process, the materials should be trimmed when lofting, and the perpendicularity of the four sides should be ensured, for example, 18 400mm * 400mm rectangular plates can be processed on a 1250 x 2500 sheet. The material utilization rate is less than 90%, which requires 2 workers to complete the process. The second step of processing is to mainly use the CNC punching machine to carry on operations such as punching with micro connection technology. In general, when the mold is cut off, there is a 5mm gap between every two parts that is the size of the long square mold. the material utilization rate is less than 94%, and the blanking of sheets requires 1 worker to complete. Due to the adoption of micro joining technology, the rigidity of sheet metal is reduced, and accidents like drawing and coiling may occur frequently. Therefore, the processing should not be carried out at high speed. In addition, the edge debris of the sheet metal parts that are micro- joined together with traditional processing should be removed by workers after the parts being taken down.
(2) Sheet metal working procedure of CNC punching shear composite machine tool. In the process of processing parts with CNC punching shear machine tools, the process of punching first and cutting later is generally adopted, that is, the right angle shear is used to cut and separate the parts from the whole plate. The whole process is completely different from the processing technique of the CNC punching machine. The processing of the whole sheet is done once through programming, and the material is saved through the cutting. The material utilization rate is 99%, and it takes less than 10 minutes to process the same sheet. Therefore, compared with the traditional technique, the sheet metal processing method of the CNC punching shear composite machine tool has a great advantage, which is also the reason for the wide application of the CNC punching shear composite machine tool in recent years.
3. Conclusion
According to the characteristics of every part of sheet metal processing, the methods and skills of punching shear composite processing technology are introduced in detail. Of course, in the production practice of the punching shear composite machine tool, these methods are not enough, it is believed that more and better operation skills are being applied in production.
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