CNC flame cutting method of analysis reduced part deformation

CNC flame cutting method of analysis reduced part deformation

Because CNC flame cutting has the advantages of high cutting efficiency, low cost, good kerf quality, high dimensional accuracy of cut parts, and high material utilization rate, it is used more and more widely in machinery manufacturing enterprises and gradually replaced traditional manual cutting. And semi-automatic cutting, greatly improving production efficiency. Due to the high quality of the cutting seams of the CNC cutting, the tailor welding of the structural parts is relatively easy, and the appearance of the structural parts is also beautiful, and at the same time, the grinding workload is reduced and the production cost is reduced.
Flame cutting is a method in which oxygen and fuel gas are used to heat the steel plate to make it partially reach the melting point, and then use high-pressure oxygen jet cutting. It can be seen that the steel plate absorbs a lot of heat during cutting. Due to the uneven heating and cooling of the steel plate, the internal stress of the material will cause the workpiece to be cut to bend to different degrees, that is, the cutting thermal deformation; The temperature near the cut exceeds the temperature required for the elastic deformation limit of the metal, causing the plastic deformation of the steel plate to generate huge tension, causing the steel plate to shift, and causing the dimensional deviation of the part. Therefore, controlling the deviation of the part size caused by the tension generated in the cutting process and controlling the deformation of the part during cutting has become the key to cutting. Now we introduce several common typical cases with layout drawings to analyze various methods of controlling deformation for your reference and reference.

Small first and then big

When the steel plate is cut as a whole, the order of parts cutting is very important to prevent part deformation and base material displacement. Generally, small parts are cut first, and then larger parts. When discharging, it should be noted that larger parts should be placed at the back end, as shown in Figure 1.

Layout example from small to large

Figure 1 is a drawing of a 16mm thick steel plate. The cutting sequence should be from left to right, the small parts on the left are cut first because the tension generated when cutting small parts can not affect the subsequent base material and make it shift, and the large parts on the right leave some 20-30mm The long sections are not cut. One is to prevent the long parts from being bent and deformed due to uneven heating of thermal cutting, and the other is to make the parts and the base material into one body so that the tension formed during cutting cannot displace the base material. , So as not to cause part size deviation, or even unable to continue cutting.

First inside and then outside

Layout example from inside to outside

If there are small parts in the hollow of a larger part, cut the small parts inside first. Figure 2 is a drawing of a 20mm thick steel plate. The cutting sequence is the same as that shown in Figure 1, and from left to right. The principle is the same as that in Figure 1. When cutting hollow parts, you should follow the principle of first inside and then outside, that is, cut the small parts inside first, to prevent displacement after the hollow parts are cut, or even the hollow parts fall off the cutting platform, causing the small parts inside to be unable to continue cutting The phenomenon.

Leave a breakpoint

In the process of blanking with a CNC flame cutting machine, the blanking and cutting of long and wide parts with relatively large length and width are often encountered. Because flame cutting is thermal cutting, a large amount of heat is absorbed during the blanking process, and uneven heating can easily lead to vertical bending and deformation of the workpiece (known as the bullhorn shape), which may cause the workpiece to be scrapped in severe cases. For this reason, the production of the factory needs to adopt reasonable cutting methods and anti-deformation measures to reduce the cutting deformation of the workpiece during blanking.

Layout examplewiththree breakpoints

Figure 3 is a discharge drawing of a 20mm thick long material. All its straight edges are common, which reduces the amount of cutting and saves a lot of time and gas consumption. In addition, it can be seen from the figure that a 20-30mm long breakpoint must be left when the long strip parts are installed, which is equivalent to multiple strips tightly tied together. It can effectively control the plastic deformation and thermal cutting of the strip parts. The displacement caused by the time tension is also the most effective and practical method in practical production. The longer the part, the more breakpoints are left. This is because the longer the interval between the breakpoints, the greater the deformation allowance of the elongated part, which is still prone to vertical bending. Especially when cutting to the last few strips shown in Figure 3, since the attached base material is getting less and less, it is necessary to leave more breakpoints to make it difficult to produce vertical bends, otherwise, it will appear as shown in Figure 4 (Note: Figure 4 is a partially enlarged schematic diagram of deformation of the 14th strip in Figure 3 with only two breakpoints left in the middle of the 12th to 14th strips. The 14th strip is severely deformed, causing deviations in the size of the parts and even scrapping. If 3 breakpoints are left in the middle as shown in Figure 3 to reduce the breakpoint spacing, the vertical bending deformation of the last few strips can be greatly reduced, and the size deviation after cutting can be reduced. When cutting with a breakpoint, the number and position of the breakpoint should be reasonably determined according to the length and width of the long strip. Under normal circumstances, when the length is constant, the wider the width, the fewer breakpoints, and vice versa. Of course, the more breakpoints are not the better, because there are more breakpoints, the flame perforation will take more time; in addition, after the steel plate is cooled, the breakpoints need to be cut by hand, which will greatly affect the surface of the slitting quality.

Deformation under three breakpoints

The frame is fixed

Layout example with breakpoints of arc slab

For thinner plates, the deformation and displacement of the parts can be controlled by leaving breakpoints. However, if the steel plate is thicker, it is very difficult to perforate, which will take a lot of time and will greatly reduce the life of the cutting nozzle. Leaving breakpoints will greatly increase the number of perforations, resulting in low cutting efficiency and higher cutting costs. Figure 5 is a spliced arc plate of a large flange with a thickness of 60mm. To prevent deformation and displacement of the parts, many breakpoints must be left to control, otherwise, it will cause a change in the arc and make the assembled flange not reach Size requirements. The way to solve these problems without leaving breakpoints or deforming, according to the author's many years of experience, is to leave the arc plate in a closed frame (see Figure 6), leaving 20-30mm wide on each side of the frame The remaining material edge is equivalent to a breakpoint, which plays the role of binding the arc plate together, so that the arc cannot be deformed, and at the same time, it can prevent the huge tension generated during cutting, and avoid the arc plate caused by leaving a breakpoint. The defect of scarring on the surface of the slit.

Layout example for framework of fixed

This article introduces in detail the measures taken to prevent the displacement of several common parts from deformation and tension caused by CNC flame cutting, and analyzes it to provide reference and reference for everyone in actual work. The above is only a rough analysis of several methods. In practice, the selection of arc ignition point, cutting sequence, and cutting direction, etc., have a great relationship with effectively reducing the deformation and displacement of parts. Should be selected according to the specific situation.

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