Lightweight body requires a large number of high-strength sheet materials for body stamping parts, and improving the manufacturing technology of high-strength plate parts has a good development prospect. TRIZ is a knowledge-based, human-oriented, systematic approach to solving problems. This project takes the left/right front longitudinal beam of a certain vehicle model as an example, and innovatively uses the methods of causal analysis and contradiction analysis in TR|z theory to try to solve the problem of stamping high-strength plates. The problem of flanging cracking also provides a reference method for solving problems in other fields of stamping. One of the core contents of TR | z theory is the law of technological system evolution (law), which can predict future technology (product) development trends according to the evolution law of technological systems, and help enterprises develop new competitive products. In this paper, by introducing the characteristics of the inner panels of the left and right front longitudinal beams of a certain model, the flanging cracking problem encountered in the production process is expounded, and the TR|z theory is applied to summarize the analysis method of the flanging cracking problem of this kind of structural stamping parts .
Product characteristics and production problems of left and right front longitudinal beams
Product process
The shape of the parts of the left and right front longitudinal beams of a car is relatively complex. As shown in Figure 1, the product size reaches 170mm × 840mm and is made by laser tailoring of two 590MPa grade dual-phase high-strength plates with different thicknesses. 590MPa grade dual-phase high-strength plate has many difficulties in the production of complex drawn parts in cold stamping production. The overall tailoring of materials with different materials and different material thicknesses will cause differences in the strength and thickness of adjacent materials, resulting in uneven feeding during the forming process. In addition, the high carbon content of the high-strength plate itself will affect the quality of the weld. , resulting in the extremely difficult forming of the high-strength plate itself with obvious edge effect, especially after stretching, affected by thinning and hardening, the edge effect is worse, and the flanging is very easy to crack.The product process plan includes drawing, trimming, punching, separation, shaping, flanging, upper flanging, and side punching, as shown in Figure 2.
production problems
During the simulation analysis of this part, the whole part is in a safe state as shown in Figure 3, and the local maximum thinning rate is 181%, which meets the material performance requirements. During the actual production preparation process, the workpiece appeared flanging and cracking at the position shown in Figure 4. In the later stage, through repeated debugging and testing, and by replacing the trimming inserts, the sharpness of the trimming edge was guaranteed. The mold was produced continuously for 2 months. A total of 10,000 pieces are no problem.During subsequent normal production, it was found that the trimming edge could not maintain a high sharpness, and the production stability was poor. In response to this phenomenon, several rectification work was also carried out, but the effect was not obvious.
problem analysis
The ultimate goal of Qian innovation is to ensure that the inner panel flange of the front longitudinal beam will not crack, and there will be no edge effect. The problem that needs to be solved is that during the flanging process of the inner panel of the front longitudinal beam, the edge formability of the high-strength panel is poor. During the production process, if the inner panel of the front longitudinal beam exceeds a certain limit, cracks will occur. The solution is to use various effective resources, personnel capabilities, product shape, material properties, process design, tooling quality, and build the system | There is no high-strength plate edge effect.
resource analysis
According to the nine-screen method, we conducted a detailed analysis of the front longitudinal beam stamping process and surrounding resources, and obtained the nine-screen resource list as shown in Figure 6.Using the ideas obtained from resource analysis, the front longitudinal beam flanging process can be replaced by new processes such as powder forming and hot forming.
causal analysis
Figure 7 shows the causes of the front longitudinal beam flanging cracking problem through the causal analysis of the technical system.Through causal analysis, the main reasons for the flanging cracking of the front longitudinal beam are the poor technological design of the front longitudinal beam product, the failure to identify the risk of flanging cracking here in the early stage, and the maintenance cost of mold tooling.
High difficulty, extremely high requirements for fitter ability, poor maintenance quality, sheet edge performance is lower than its own performance index, and there is a contradiction between flanging and cost in process design
Component Analysis
By trimming some harmful factors in the system, the trimmed model diagram is obtained. As shown in Figure 8, through trimming analysis, the idea of solving the flanging cracking of the inner panel of the longitudinal beam is obtained. Through product optimization or process optimization, the high strength is reduced or eliminated. Flange at the arc of the plate, and directly meet the product requirements through stretching and trimming locally.
Contradiction Analysis
Analysis plan 7
According to the causal analysis, the reason for the cracking of the flanging edge of the high-strength board is that the product has poor craftsmanship. Changing the flanging length of the product will improve the cracking of the high-strength board flanging, but it may cause the strength and assembly of the entire product to deteriorate. This pair of technical contradictions are as follows: The improved parameters—the length of the stationary object—and the deteriorating parameters—the strength. At the same time, the physical contradiction that the product flanging height directly affects the probability of flanging cracking is obtained. This contradiction can be solved according to the space separation in the physical contradiction.
Analysis plan 2
According to the causal analysis, the reason for the cracking of the flanging edge of the high-strength plate is the insufficient trimming quality. By changing the trimming quality, the flanging cracking phenomenon of high-strength panels can be improved, but the maintainability of the entire tooling may be poor. This pair of technical contradictions is a parameter of improvement—manufacturing precision and a parameter of deterioration—maintainability. At the same time, the physical contradiction that the sharpness of the trimming edge directly affects the probability of flanging cracking is obtained.
Analysis plan 3
According to the causal analysis, the reason for the cracking of the flanging edge of the high-strength board is the insufficient performance of the edge sheet. By improving the properties of the sheet, the flanging and cracking phenomenon of the high-strength sheet will be improved, but the difficulty of manufacturing the sheet will be increased. . At the same time, the physical contradiction that the material properties directly affect the flanging cracking probability is obtained. This contradiction can be solved according to the separation of the system level in the physical contradiction.
Analysis plan 4
According to the causal analysis, the reason for the cracking of the flanging edge of the high-strength plate is that the forming margin is insufficient during flanging. Cancellation of flanging can eliminate flanging cracking, but it will increase the number of tooling and reduce material utilization. This pair of technical contradictions is the improved parameter—manufacturability and the deteriorating parameter—the weight of the stationary object. At the same time, the physical contradiction that the flange height (Fig. 9) directly affects the flange cracking probability can be obtained. It is solved according to the separation of space in the physical contradiction.
Object field analysis
According to the functional analysis, S2-plate, Sl: drawing part, F: mechanical field, the functional model is represented by a symbol system, as shown in Figure 10.According to the analysis of the object field, the analysis scheme 5 is obtained, which reduces the size of the sheet and increases the safety margin before flanging. The result of the scheme is shown in Figure 11.
plan selection
The solutions proposed above are summarized, and the list of solutions to the longitudinal beam cracking problem is shown in Table 1. Through the theoretical comparison of the schemes and the actual production verification, the evaluation list of the solution to the cracking problem of the longitudinal beam is shown in Table 2.According to the above analysis, the preferred options 1, 3, 4, and 5 are the best in terms of economy and feasibility.
concluding remarks
With the intensification of the development trend of economic globalization, the competition is becoming more and more fierce. In order to utilize and allocate various resources more rationally, enterprises not only need to understand the technical status of current products, but also grasp their future development trends. Therefore, accurate and reliable analysis of product technology evolution has become more and more important. In this paper, by applying and using TR Based on the analysis methods of resources, components, causality, and contradictions of the billion theory, combined with the actual production, the problem of flanging and cracking of longitudinal beams in the stamping field is introduced in detail, which provides a reference for the analysis and solution of problems in the stamping field.
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