Abstract: With the take-off of my country's economy and the rise of the whole machine equipment manufacturing industry, my country has become one of the largest manufacturing countries. As important cutting equipment, CNC flame cutting machine, CNC plasma cutting machine and CNC optical fiber cutting machine are widely used in the construction machinery industry. However, in the actual application process, cutting quality problems are often accompanied by CNC flame cutting. This paper combines the reasons for the quality problems that often occur in the processing process of our factory, and reduces the quality problems in the cutting process by adjusting the cutting process and cutting method. The cutting quality of the material.

1 Introduction

CNC flame cutting machine is currently a general steel plate integral processing equipment, widely used in various industries. The metal is partially melted, and at the same time, the molten metal is blown away by high-speed air flow to form a narrow slit to realize blanking. During the processing, the NC program controls the walking path. Because of the high degree of automation, large cutting thickness and low cutting cost of CNC equipment, most of the important equipment for steel plate blanking in manufacturing enterprises use CNC flame cutting machines. However, in the process of flame cutting, cutting defects often occur, resulting in poor quality of the cutting surface and affecting the quality of the product as a whole. In particular, due to the large heat input affected area of flame cutting, the workpiece is deformed due to heat input during the cutting process. Such problems directly affect the welding of structural parts. Based on the problems encountered in the actual processing process of our factory, this paper analyzes the methods to improve the cutting quality and control the thermal deformation of cutting.

2. Analysis of cutting surface defects and causes of CNC flame cutting during processing

2.1 Cut surface defects and cause analysis

Flame cutting in our factory is mainly used for steel plates with a thickness of 24mm-120mm. The following defects often occur during the cutting process:

2.1.1 Collapsing edge: The reason for the defect is that the cutting oxygen pressure is too high and the cutting speed is too slow during the cutting process.

2.1.2 The concave defects in the cutting surface are mostly caused by the high cutting oxygen pressure, the excessive distance between the cutting nozzle and the steel plate, the blockage of the cutting nozzle causing the air line to be incorrect, and the oxygen purity is low.

2.1.3 Defects caused by the inclination of the cutting surface are mostly due to the fact that the cutting nozzle is not perpendicular to the steel plate and the wind line is inclined.

2.2 Control method of quality defect of cutting surface:

From the above reasons, it can be seen that there are many factors that affect the quality of the cutting surface. During normal processing and production, the corresponding cutting speed, cutting oxygen pressure, and combustible gas output pressure should be selected according to different plate thicknesses. The purity of cutting oxygen is also very important in the cutting process. When the remaining parameters are selected properly, liquid compressed oxygen with a purity of ≥99.5% is used for cutting. It can be seen that the quality of the cutting surface has a relatively obvious improvement in visibility, which effectively alleviates the problems in the cutting surface. concave problem. At the same time, the cutting nozzle should be used correctly and cleaned up in time. The quality of the cutting nozzle also has a great influence on the processing quality of the cutting surface.

3. Deformation causes and trends of parts with large length and width in CNC flame cutting machine

Taking the main blade of the bucket in our factory as an example, its length and width are relatively large, and there are many slender parts. When using CNC cutting machine, CNC plasma cutting machine and CNC optical fiber cutting machine to cut parts on the steel plate base material, due to the uneven heating of the steel plate. , the plate is partially expanded under the influence of high temperature heat input, and the surrounding base metal that is not affected by heat input will limit its expansion, and the steel plate will deform at this time. When the CNC cutting machine is processing, the displacement path of the cutting nozzle is controlled by the CNC program, which does not change with the deformation of the steel plate. Therefore, the actual blanking and forming parts are formed by the cutting path specified by the program. The theoretical size of the workpiece will have a big difference due to the deformation of the steel plate, which is what we call thermal deformation and size tolerance.

During the processing of the main blade of our factory, due to the uneven heating of the two long sides, the longitudinal bending of the slat, the width of the two ends are inconsistent, and the width and size are out of tolerance.

4. Control method of cutting deformation of parts with large length and width ratio

4.1 Determination of cutting direction

When determining the cutting direction, the last edge should be connected with most of the remaining material of the base metal. If the workpiece and most of the remaining material of the base metal are cut and separated first, the workpiece will be cut due to thermal deformation stress during processing. During the process of displacement, the workpiece size is out of tolerance and deformation occurs.

4.2 Application of "Retention and Cut"

In the cutting nesting program, set one or several parts of 5-20mm on the cutting edge not to cut, it is the workpiece and the base metal to understand through these uncut parts, and the base metal is expected to hold the workpiece to avoid cutting. The workpiece is displaced due to the thermal deformation stress during the cutting process, reducing the shrinkage of the workpiece after cooling, which some companies call "bridge" cutting. However, these reserved parts also need to be cut after the entire base metal steel plate is processed, which increases the number of perforations and preheating time, and the "reserved cuts" will produce large bulges, which need to be polished, which is time-consuming and laborious. It has a great impact on the overall production efficiency.

4.3 "Punching long strip" processing

When processing the main blade, adjust the size between the air lines of each cutting gun to ensure that it is consistent with the width of the main blade. The length direction of the base metal runs in a straight line to ensure the width of the main cutter plate. The length of the running is consistent with the length of the main cutter plate, and it runs in the opposite direction parallel to the width of the base metal. Assuming that 6 main cutting boards are processed at the same time, a total of 7 cutting torches are required. The seven cutting torches are regarded as a whole, and their walking path is A→B→C→D, as shown in Figure 3, the circle in the figure is the cutting torch. . After cutting and blanking, the size of the workpiece can be effectively controlled, and the problems such as workpiece deformation and oversize can be reduced. This method cannot directly measure the distance between the wind lines, so the adjustment of the wind line distance of the cutting nozzle will have a large difference due to different operators, and the process is relatively unstable.

5 Conclusion

To sum up, to improve the cutting quality of CNC flame cutting machine, there are many factors to consider. CNC flame cutting has strict requirements on the purity and pressure of the gas used; the selection of reasonable process parameters also has a great impact on the cutting quality; and the method of nesting, cutting sequence, cutting direction, etc. should be continuously practiced. Technicians, programmers and field operators have high requirements. Similarly, for the operation of CNC plasma cutting machine and CNC optical fiber cutting machine, we should also pay attention to these aspects.