Cutting force analysis and cutter design of the ho

2022-07-27
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Stress analysis and cutter design of rectangular steel tube without supporting core

rectangular steel pipe is a widely used material in the manufacturing industry of vehicles, household appliances, cabinets and frames, with many length specifications and large production capacity. The stamping processing methods of rectangular steel pipe mainly include cutting, cutting, punching, bending, roll forming, etc. the first process is cutting. In the past, grinding wheel cutting was often used for cutting. Due to the slow speed, large cutting burr, and the high temperature generated during grinding wheel cutting, the cutting place was oxidized and blue. In addition, the burr became hard, so the treatment was troublesome, the productivity was low, and the grinding wheel cutting dust pollution and noise were large. However, many shearing methods can greatly improve the productivity by adopting the beneficial conditions of stamping China's extruder industry in terms of foreign trade export in 2013. According to the experience of cutting round steel pipes with the strong punching method, the so-called strong punching method is to punch a notch on the side of the pipe, and then turn 90 ° to the next station for cutting. Although the speed, efficiency and quality have been greatly improved, they still can not meet the needs of mass production

for rectangular steel pipes, new methods and processes must be found to meet the production needs. This paper mainly introduces the stress analysis and cutter design of rectangular tube cutting without supporting core, and makes some superficial research on it

1 process analysis

Figure 1 is a cross-sectional view of a Q235 rectangular steel pipe. Bone 20 mm x 50 mm x 2mm and 25 mm × 75 MMX 2mm

steel pipe stamping refers to the second processing of steel pipes, which belongs to the category of steel pipe deep processing technology. It is a new processing technology developed from the traditional stamping process. The stamping processing methods of steel pipe materials mainly include cutting, cutting, punching, bending, roll forming, etc. The most widely used in actual production is cutting off

in production, the cutting of steel pipes is usually classified as threat. One is mechanical cutting, such as turning, sawing, grinding wheel cutting, etc. the other is punching cutting method. Comparatively speaking, the quality of mechanical cutting is stable, but the productivity is low. The stamping and shearing method can greatly improve the productivity. As long as the process is appropriate, the quality of cutting section can be better guaranteed. Stamping and shearing process can be divided into two types: cutting with supporting core and cutting without supporting core

As the nano material is already the material with the finest grain size at present

(1) it is only suitable for cutting short and straight steel pipes with supporting core

(2) unsupported core cutting. As the steel pipe structure requires straight pipes of various lengths, it is difficult to use mandrel, so unsupported core cutting is widely used. For the cutting of circular steel pipe, there are many examples of cutting by punching and shearing. For the cutting of rectangular steel pipe, the method of saw cutting or grinding wheel cutting is usually used

entrusted by the manufacturer, the cutting of rectangular steel pipes of various sizes, lengths and straight pipes was studied

2 stress analysis and cutter design

2.1 cutter punching and shearing pipe stress principle

when punching and shearing pipe with cutter, first try to make the shear force acting on the pipe less than the strength of the pipe itself, so that it has sufficient strength to prevent longitudinal bending and transverse collapse deformation. Because there is no supporting core in the pipe, the pipe wall at the neck will collapse under the action of punching shear force. In order to improve the cutting quality and reduce the deformation of pipe fittings, the shear force acting on the pipe wall during stamping and shearing should be distributed to the outside as far as possible. The included angle between the force direction of the rigid cutter blade on the pipe wall shear point and the normal of the pipe wall at that point a ≥ 90 ° meets the so-called "chip eversion" condition. To minimize the punching shear force acting on the pipe

2.2 stress analysis and cutter design

Figure 2 is the simulated stress diagram of the rectangular steel pipe when it is in the upright position. When punching the pipe from the top center of the rectangular steel pipe in the upright position with a cutter with an included angle of 90 °, under the action of the punching force, the tip of the cutter first contacts the center of the top surface of the pipe. During the punching process, the punching waste is broken and rolled under the bottom surface of the cutter. The top surface of the pipe is a plane perpendicular to the punching force, which is not strong enough to resist the punching force of the cutter, resulting in the collapse and deformation of the pipe wall at the neck. It can be seen from the analysis that if a notch is not pre cut, the top surface of the rectangular steel pipe cannot meet the condition of "chip eversion" when it is in the upright position

Figure 3 shows the simulated stress diagram of rectangular steel pipe when it is stopped by the strong impact method. Punch the top surface of the pipe on a pair of dies. Notch, and then turn 90 ° to the next station for cutting. It can meet the so-called "chip eversion" condition, but it has many processes and low efficiency

Fig. 4 is the simulated stress diagram when the rectangular steel pipe is inclined at 45 ° and the included angle of the cutter is 90 °. When Shanghai promulgated and implemented the Interim Measures for the management of disposable plastic lunch boxes in 2000, the tip of the cutter first cut into the circular arc of the pipe item under the action of the punching force. After a certain depth, the waste was broken and rolled under the bottom of the cutter. Although it will not cause serious collapse and deformation of the pipe wall. However, when the cutter cuts into the bottom of the pipe, the short side of the included angle of the cutter cuts the bottom of the pipe at the same time. Since the thickness of the cutter should be as small as possible in theory, it will cause poor strength of the cutter and easy to crack. In addition, the waste material from the upper part of the pipe is broken at the bottom of the cutter, which is in a disaster stable state, leaving traces when punching the bottom of the pipe and affecting the section quality

Fig. 5 is the simulated stress diagram when the rectangular steel pipe is inclined at 45 ° and the included angle of the cutter is l 20 °. When the cutting tool with an included angle of L 20 ° and a front R2 is used to punch the pipe from the top of the rectangular steel pipe with an inclined angle of 45 °, the front R2 of the cutting tool is first cut into the arc center of the pipe top to the top half of the short edge. During this process, the waste attached to the bottom of the cutting tool is not broken, and its length is longer than that attached to the bottom of the cutting tool. Under the action of punching force, the waste material is forced to extrude to the outside of the pipe, forming the so-called "chip eversion" effect. The waste is always stably attached to the bottom surface of the cutter for punching the lower half, and the punching shear force acting on the pipe is not greater than other methods

3 conclusion

the analysis of punching and shearing of rectangular steel pipe shows that: (1) as shown in Figure 2, the included angle of the theoretical contour curve of the punch blade should be small, sharp and long, and the stiffness is poor. Therefore, when punching pipe items, the punch used in actual production cannot meet the condition of "chip turning out". With this method, the pipe is flat, the strength is poor, and the pipe wall collapses and deforms greatly

(2) as shown in Figure 3, there are many processes and low efficiency

(3) as shown in Figure 4, since the rectangular steel pipe is tilted 45 °, the included angle of the theoretical contour curve of the punch blade is 90 °, the "chip eversion" condition can be met. However, the cutting waste is in a free state, which will affect the stamping and shearing quality of the lower half

(4) as shown in Figure 5, the rectangular steel pipe is also tilted 45 °, and the included angle of the contour curve of the punch blade is changed to l20 °, so that the waste attached to the bottom surface of the cutter does not break. Under the action of the punching force, the waste is forced to squeeze towards the outside of the pipe, which can form the so-called "chip turning out" effect. Moreover, the pipe is inclined, with high strength and small collapse deformation of the pipe wall

based on the above analysis. The cutter design scheme shown in Figure 5 is adopted, and the thickness of the cutter is 3.8 mm. Applied to 20 mm × 50mm × 2 mm and 25 mm × 75 mm × The 2mm curved rectangular steel pipe is punched and cut, without obvious appearance defects such as pipe wall collapse. The burr is within the allowable range, with high efficiency and good effect

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