Development process of automobile stamping dies
Traditionally, automobile consumption belongs to bulk consumption, and the service life of automobiles can normally reach more than ten years and hundreds of thousands of kilometers. However, today is an era of rapid development of the automobile industry. Intelligent generation and electrification are the trends of today's automobile development, which promotes the rapid update and iteration of automobile products. Intelligent assisted driving and car-machine systems are updated and upgraded as quickly as mobile phone systems. Faster and smarter demands also promote the continuous update of hardware (chips, sensors, etc.) to provide performance support. Therefore, at some level, automobiles are transforming into fast-moving consumer goods, with the traditional mechanical properties of automobiles weakening and the electronic properties constantly strengthening.
Rapid updates and replacements have spawned fierce market competition. In recent years, the cycle of automobile replacement is generally five years, and the cycle of vehicle development is generally more than 36 months. In the fierce market competition environment, it is not surprising that the automobile replacement cycle is three years, and the corresponding vehicle development cycle will also be greatly shortened. In the future, the cycle of 24 months may become normalized.
As one of the four traditional processes of the whole vehicle, stamping has the longest development cycle of new model molds and is one of the key paths for vehicle development. Under the new industry demand conditions, the development cycle will inevitably be gradually shortened. This article will discuss how to shorten the development cycle of automobile stamping dies.
Stamping die development process
The stamping die development process is generally divided into three stages: design, manufacturing, and debugging. The design stage consists of two parts. The first part is the early synchronous engineering (SE), which is carried out simultaneously with the styling development and body development. Based on the comprehensive optimal principle of quality, cost, and schedule (generally called QCD), the processability of the product is analyzed and the product improvement problems are proposed; the second part is the mold process and structure design after the product prototype data is released. After the design is completed, the manufacturing stage begins. First, the mold is cast. After the casting is completed, it is processed and assembled according to the drawings. After the assembly is completed, the machine action is eliminated and the interference is eliminated before delivery for debugging. Mold debugging is generally divided into off-site debugging (at the mold supplier) and in-factory debugging (in the main engine factory). Off-site debugging mainly completes the mold research and development and comprehensive improvement of parts quality; in-factory debugging mainly involves production line matching, vehicle problem solving, and production problem solving (cutting edge debris, stuck waste, etc.).
Discussion on factors affecting the development cycle and countermeasures
Design stage
High quality is designed, not manufactured. Design is the most important link in the entire product development chain. The development of stamping dies involves two aspects: synchronous engineering at the product level and the process structure design of the die itself.
Solution 1: The risk of insufficient rigidity of the engine hood outer panel of a certain model (Figure 1) was not fully identified during the product development stage. After entering the trial production stage of mass-produced vehicles, it was found that the parts were easily deformed and scrapped during the main production trial production (Figure 2). After being made into an assembly, the rigidity was also insufficient, and it was significantly easier to collapse when pressed than previous models.
The main reason for the problem was that the product's shape curvature was small (Figure 3 shows the curvature radius of the hood. The curvature radius is large and the corresponding curvature is small). The final solution was that the process and product design departments jointly adjusted the product shape to increase the product curvature. After completion, the mold profile of the entire process was re-machined to enhance the rigidity of the product. The entire rigidity topic rectification lasted more than 2 months, which had a great impact on the quality of the mold.
Solution 2: The flange of the front floor of a certain model (Figure 4) is 90°, and the process design stamping direction is also 90°. The rebound angle is not preset (generally set to 3°). During the mold trial stage, the flange showed obvious rebound (rebound amount was more than 1mm, and the benchmark was within 0.5mm). The countermeasure was to reduce the flange gap by 0.15~0.2mm. There was no abnormality in the single machine test punching, and the flange rebound was also well controlled, and the accuracy met the requirements. After returning to the busbar batch production, only about 30 units were produced, and the flange began to be strained and cracked (Figure 5), and large-scale production could not be maintained.
The main reason for this problem is that the rebound angle is not set in the process setting, and the rebound of the part cannot be completely eliminated. In addition, the plate used for this part is a bare plate, which is brittle and has poor tensile resistance, which aggravates the problem. The final solution is to change the drawing process, draw the flange surface for pre-forming, and finally control the rebound amount within 0.8mm, which does not affect the welding of the whole vehicle. After the mold returned to the busbar, it took about 2 months to solve the strain issue alone. Finally, changing the drawing mold was very costly for simple floor parts.
From the above cases, we can see that the quality of product design and mold design has a considerable decisive effect on the quality of later product manufacturing, and also has a significant impact on the length of the debugging cycle. Design work is not evaluated by the completion node, but by the quality of the final product and the durability of mass production. There needs to be good cooperation and interaction between process and product. Product design should consider the objective reality and general rules of process and manufacturing. Process design needs to focus on case accumulation, verification of past bad problems and the establishment and maintenance of the standard system, and regular summary and update. For the use of new product features and new processes, there should be a reserve plan, which will be used when the problem cannot be solved. After the model is completed, a written summary of the subject should be formed as soon as possible, and the standard documents should be updated. Invite colleagues with rich experience in workshop and on-site debugging and maintenance to participate in the drawing review, close to the production and manufacturing site.
Technological innovation is also indispensable. For large innovations and no backup plan in the manufacturing stage, it is recommended to open a test mold. For small innovations, as long as there is a reserve plan, you should boldly try to promote product strength. A product with mature technology has a short production cycle. A product with good sales has strong product strength. Good workmanship and high product strength is an eternal topic.