A method to improve the structure of B-pillar trimming process

Yu Jia·Jilin FAW Fourth Ring Non-standard Equipment Manufacturing Co., Ltd.
Pan Yuanan·Mechanical Engineering College of Changchun Automobile Industry College
A certain model adopts a one-piece fully enclosed side panel reinforcement structure. The OP20 trimming mold has problems such as poor decline of waste materials and excessively long partial trimming burrs on the parts. Considering the overall process, by adjusting part of the trimming work of the OP20 trimming mold to the OP40 punching mold, the trimming sequence and process structure of the upper part of the B-pillar are changed. The results show that the burrs on the parts are eliminated, and the waste falls smoothly, achieving the goal of improving production efficiency and product quality qualification rate.
With the enrichment of automotive products and the application of new materials, consumers are paying more and more attention to the safety of the entire car. The side panel reinforcement is a key part of the body side panel assembly, and it is the reinforcement and support of the side panel outer panel. The quality of parts and its products directly affects the manufacturing accuracy and safety of the vehicle. The side wall reinforcement plate has the characteristics of complex structure, high strength, difficult forming, and large trimming and punching force, so higher requirements are put forward for the mold material and trimming process. Mold structure design is the most important thing, which directly affects the quality of parts. For parts such as side wall reinforcement plates, the unreasonable mold structure design will directly lead to an important quality defect-large trimming burrs, which is a common defect in automobile stamping parts and also affects the size and accuracy of stamping parts One of the important problems of the welding machine has a serious impact on the welding accuracy and even the accuracy of the whole vehicle. It has also become an important factor affecting the quality and production efficiency of the car body. In this paper, through the modification of the trimming process structure of the reinforcing plate of a certain vehicle model, the problem of poor decline of scrap and the burr caused by the part is optimized and rectified, and it provides a reference method for solving similar problems of subsequent models.
Figure 1 Stamping process of side panel reinforcement
Process and material introduction
The side wall reinforcement plate production method is closed automatic production, the beat is 10 times/min, and the stamping process is: OP10 drawing forming process, OP20 is the trimming process, OP30 is the shaping process, and OP40 is the punching process, as shown in Figure 1. Shown. Through four processes of stamping, the process from sheet metal to finished part is realized.
The partial inserts of the OP20 trimming die are made of SKD11 (alloy steel), and the parts are tailor-welded plates of 590R/TRIP800/TRIP600. The material distribution map of the tailor-welded plate and the material details of the tailor-welded plate are shown in Figure 2.
Problem Description
In the production process of the side panel reinforcement of a certain vehicle model, the OP20 trimming process of the part often showed that the waste material did not slide smoothly on the upper part of the B-pillar, as shown in Figure 3. As a result, the monthly downtime rate of molds reached 20% and the scrap rate of parts reached 10%.
Figure 2 Tailor-welded blank material distribution map and tailor-welded blank material details
Figure 3 Integral tailor-welded reinforcement board
The insert on the upper part of the B-pillar of the trimming mold is severely damaged, and there is some “slag drop” in some parts. It must be repaired and welded repeatedly before continuing to use. As mentioned above, the trimming insert is made of SKD11, and special welding is required during maintenance: the insert needs to be kept warm for about 6 hours, and the special electrode for SKD11 material (NH610 model) is used for welding, while welding and hammering to eliminate welding Stress, after welding, it needs to be cooled to room temperature with the furnace. In the absence of heat preservation welding or improper welding operation, the inserts will appear cracks or even cracks, and in severe cases, production will stop.
Another problem with damaged inserts is part burrs. The measured trimming burr is about 0.75mm, and the normal length of the burr is 7% to 12% of the thickness of the sheet. The thickness of the sheet is 1.5mm, which exceeds the limit value of 0.57mm for the burr, which seriously affects the subsequent welding quality and operators. Safety.
Cause Analysis
The end face of the B-pillar of the workpiece is trimmed using a hanging wedge piercing and trimming structure. After cutting and trimming, the waste at the position of the “piercing knife” is in the shape of a semicircular socket and is wrapped on the piercing knife. When the trimming is cut again, a stacked trimming is formed, causing the cutting edge to “gnaw”, as shown in Figure 5.
Figure 4 Burr location of the workpiece
Figure 5 The position of the edge trimming defect of the B-pillar of the workpiece
The past experience of blocking waste can not fundamentally solve the problem of nest-shaped waste, and we need to find another way. Throughout the overall process, the trimming process can be divided into OP40 punching process. Because only the OP40 punching process has space for trimming inserts, it is not easy to wrap waste and has no adverse effects.
Based on the above analysis: cancel the partial upper and lower die trimming process of the OP20 trimming process, change the OP40 punching process to the OP40 trimming punching process, and increase the trimming insert and the reverse mechanism. In this way, the scrap can not only slide smoothly, but also can eliminate the burr defects of the part.
In accordance with the order of the stamping process, the rectification of the mold is gradually carried out. Split the original OP20 trimming process “problem” waste into two processes. Part of the OP20 trimming process is reserved, and the remaining part is adjusted to the OP40 punching process. It can be simply expressed as scrap A is split into scrap B and scrap C, that is, A=B+C. The specific implementation steps are as follows:
⑴OP20 makes the following rectifications on the mold trimming process (Figure 6): 1) The upper mold cancels the “piercing knife” and changes to trimming structure, that is, changing from the original hanging wedge trimming to the ordinary straight trimming structure. 2) The lower mold cancels the sharp piercing corners, and adds the straight trimming insert of the lower mold. 3) Make new B-pillar trimming inserts, and replace the inserts that are “broken” and repeatedly repaired. The trimming datum can be restored to solve the large defect of trimming burr here.
⑵ The following rectifications were made to the OP40 punching process (Figure 7): 1) Add end trimming inserts, and trim off the nest-shaped waste left at the “piercing knife” in the OP20 trimming process after the modification. 2) Increase the anti-side mechanism to offset the lateral force generated when cutting the nest-shaped waste, and increase the waste chute to ensure that the nest-shaped waste slides smoothly.
Figure 6 OP20 trimming process rectification content
Figure 7 OP40 mold process rectification content
Effect of implementation
After changing the mold structure and stamping process of the side wall reinforcement plate, the OP20 trimming process blockage problem was successfully solved, preventing the trimming oblique wedge cutting edge caused by the difficulty of the scrap falling from “gnawing”, reducing the frequency of mold maintenance and increasing The production efficiency of the production line. Based on the calculation of 40,000 pieces per year, the scrap rate is reduced from 10% to zero, and the cost of the side wall reinforcement plate is 300 yuan/piece, which saves a total of 1.2 million yuan in material costs; the mold shutdown rate is reduced from the original 20% to 2.5%, according to the equipment shutdown The cost is 7,500 yuan/hour, which saves a total of 87,500 yuan in equipment commissioning costs. In the case of ignoring maintenance costs and labor costs, a total of about 1.2 million + 87,500 = 1,287,500 yuan was saved every year during the life cycle of the model. The effect of problem rectification is shown in Figure 8.
Figure 8 Effect of problem rectification
Concluding remarks
This article takes the modification of the trimming process of the side wall reinforcement plate of a certain car model. By changing the trimming process sequence and standardizing the trimming insert repair standard, it has successfully improved the poor decline of trimming waste, mold shutdown and products. A series of problems affecting production efficiency, such as the qualification rate, provide solutions to the design and maintenance of the side panel reinforcement molds for new models in the later period, and also contribute to the growth and development of domestic models.