Influence of half cone angle on thinning and deep

2022-08-19
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Influence of half cone angle on thinning and deep drawing in numerical simulation of motor shell

with the continuous development of processing industry and the development of processed products towards high precision, high quality and high difficulty, multiple forming and special forming methods of sheet metal are being more and more widely used. Motor shell is a part with high surface quality and precision requirements, and its inner and outer walls need to be thinned and drawn. However, thinning and deep drawing often encounter such problems in actual production: when the thinning amount is certain, due to the unreasonable selection of die parameters, it is easy to crack or break the cylinder wall during deep drawing; Or we need to add another thinning and drawing process, resulting in the increase of die cost. Practice has proved that the half cone angle is a key factor when other conditions such as material, friction and thinning are certain. (see Figure 1)

Figure 1 die half cone angle a

as for the selection of half cone angle, there is no accurate formula, curve or table at present. Some professional books and relevant manuals only provide that the half cone angle tightening force is applied through a hydraulic piston with a diameter of 32mm, and the tightening continues until the pressure reaches the approximate range of 17.2mpa, which is inconsistent. For example, some literatures give a half cone angle of 10-30 degrees, while others give a half cone angle of 12-25 degrees. If the cone angle is too small, the thinning forming tends to be close to extrusion thinning, which increases the friction resistance; Excessive cone angle makes it more difficult to thin and draw, and increases the total forming force. Therefore, how to deduce the optimal half cone angle under certain conditions? Some people have used the work balance method to deduce the display expression of the optimal half cone angle under considerable assumptions and simplified conditions, but they have not done detailed and in-depth research and discussion

through the application of computer numerical simulation technology, this paper studies the influence of half cone angle on the close relationship between talent and innovation of total forming force, so as to select the appropriate half cone angle in the thinning deep drawing of motor shell, ensure the rationality of deep drawing, and provide the basis for die design at the same time

1. Product analysis

the plane dimension drawing and part drawing of the motor housing are shown in figures 2 and 3:

Figure 2 the size of the motor housing Figure 3 the finished part of the motor housing

it can be seen from figure 1 that the forming of the motor housing is complex, and the main process is the forward drawing of the inner circle and the reverse drawing of the outer circle. The inner and outer shells and the bottom wall thickness of the parts are different, so it needs to be thinned and deep drawn. In addition, the thinning amount of the side wall is large, and the bottom fillet is small, which requires good surface quality, high precision, and no deformation, scratches, wrinkles and other defects. Its structure is an axisymmetric cylindrical part, so it can be treated by the deep drawing method of cylindrical parts. This paper mainly studies the thinning and deep drawing process of the outer wall. The material used for the motor shell is 37 steel (dqsk), and the material thickness is t=1.6mm

2. Pro/e three-dimensional modeling and numerical simulation

2.1 three-dimensional modeling

as shown in Figure 4 is the schematic diagram of thinning and deep drawing die for semi-finished motor shell:

Figure 4 thinning and deep drawing forming schematic diagram

in the figure, the half cone angle of the die is generally in the form of guide angle rather than fillet, and the use of fillet to increase the forming friction will cause great loss to the die and is not conducive to thinning and forming

2.2 DYNAFORM deep drawing numerical simulation and result analysis

DYNAFORM simulation software is used to analyze the thinning forming process. LS-DYNA is used as the solver. Based on the finite element theory of incremental method, the analysis results are accurate and reliable. All default parameter settings of the software are applied to stamping analysis. Before using DYNAFORM for analysis, it is first necessary to convert the file generated by pro/e into the IGS format recognized by the software, and then import the file. If the imported file information is defective, it can be repaired with the function of DYNAFORM software itself to meet the requirements of simulation

1) determine the simulation parameters

<2. Some interfaces are the same p> drawing type: inverted draw

contact type: forming_ One_ Way_ Surface_ To_ Surface ;

blank: material type 37 (a 3-parameter ideal model in sheet metal forming simulation, plane stress state, anisotropic material), attribute: beytschko_ Tsay shell, thickness direction integral point nip:5

punch: rigid body, static friction coefficient: 0.125, dynamic friction coefficient: 0.1, moving speed: 8000mm/sec; NIP:3;

female die: rigid body, static friction coefficient: 0.125, dynamic friction coefficient: 0.1; NIP:3;

blank holder: rigid body, static friction coefficient: 0.125, dynamic friction coefficient: 0.1; NIP:3;

2) simulation results of thinning and deep drawing

by controlling parameters such as blank shape, blank holder and die half cone angle, the simulation results are close to the actual situation as much as possible, so as to obtain qualified products with high quality. In addition, there are influences of die half cone angle and primary thinning rate in the process of thinning and deep drawing. The half cone angle is generally between degrees. In this paper, 15 degrees is selected. If the thinning rate exceeds the critical thinning rate of the material, the workpiece will crack, and it must be thinned and drawn several times. Generally, the critical thinning rate is 0 Between 30. The thinning rate of the shell (T-T ')/t= (1..45)/1.6=0.09 is far less than the critical value, so one-time deep drawing will not produce cracks. The following simulation results also illustrate its correctness

figure 5

3 The influence of half cone angle on the total forming force

in thinning and deep drawing, the half cone angle has little effect on the final forming quality of the outer circular wall, but has a great influence on the total forming force of the die. Therefore, choosing the best half cone angle structure is conducive to reducing the total forming force and the requirements of products for equipment

set the die half cone angle a as 5, 10, 15, 20, 25 and 30 respectively. When modeling the die, you can use the part family command of pro/e to only change the cone angle, which can save a lot of repeated modeling process. Under the condition of constant thinning thickness, the influence of different cone angles on the total forming force is studied by simulation, and the half cone angle in motor thinning forming is found. The value of the total forming force at different cone angles obtained by numerical simulation is shown in Table 1: Table 1 the influence of the half cone angle of the female die on the total forming force

half cone angle

5

10

15

20

25

30

total forming force (KN)

38.0

38.4

38.5

39.0

41.3

41.8

it can be seen from the table that, on the whole, the total forming force does not change much in the range of 50 ~ 300, However, there are still small differences. See Figure 6 for details:

Figure 6 half cone angle and total forming diagram

from the figure, the total forming force of the half cone angle shows an upward trend between 50 and 300, but the change of the total forming force is very small between 5 and 15. Considering that a small angle will increase the friction between the die and the material, 15 is finally selected as the half cone angle in the thinning and deep drawing of the motor shell

4. Conclusion

this paper analyzes the thinning and deep drawing process of motor shell, and studies the influence of half cone angle on the total forming force. The forming process is analyzed by finite element numerical simulation. According to the analysis results, the optimization of the half cone angle of the female die can significantly reduce the total forming force, reduce the requirements of production equipment, and the products also meet the requirements of actual production. In addition, the use of numerical simulation technology can shorten the mold development cycle and improve the economic benefits of products

references

Tu Guangqi Stamping die technology, mechanical industry press

Xu Zhengkun, stamping dies and equipment, mechanical industry press 2005

ZHENG Jiaxian, stamping process, therefore, for testing the tensile properties of flexible packaging materials, it is necessary to equip with a larger stroke tensile machine and practical technology of die design, mechanical industry press 2005

JIANG Kuihua, stamping process and die design, Mechanical Industry Press 2002

Wang Xiaopei's stamping manual (Second Edition) [m] China Machine Press, 1988

Zhao Haiou LS_ DYNA dynamic analysis guide [m] Ordnance Industry Press, 2003

about the author:

Yan Jianjun, male, from Huainan, Anhui Province, master's degree, mainly engaged in cad/cae/cam research, address: Fengde technology company, room 1707, jinwantong building, No. 394 Meiling Avenue, Hefei, zip code: 230022,: (0551), E_ mail:calens@(end)

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