Ideas and methods for cost control of body in white stamping parts

With the increasingly fierce competition in the automobile market, the main engine manufacturers have begun to focus on the cost control. The cost of BIW has been confirmed more than 95% in the design stage. Once the tooling is developed, the amount of process improvement and influence will be very small. During the development of Se, the process, cost, quality and other factors of stamping parts in the whole life cycle are fully considered. The process review and process planning of stamping parts are paid attention to, and the parts meeting the product requirements are developed with the optimal process methods and means.
BIW cost components
BIW cost (Figure 1) mainly includes stamping cost and welding cost. The main influencing factors of welding cost are the number of solder joints, weld length, tooling allocation and auxiliary materials, which are mainly determined by product design; the main influencing factors of stamping cost are raw materials, production process and tooling allocation, of which the raw material cost is mainly affected by material utilization rate and material specification, and production cost It is mainly determined by the process quantity and production tonnage, and the tooling allocation is mainly the development cost of mold, clamp and inspection tool. Stamping cost is the key factor affecting the cost of BIW (accounting for 80%), and the cost has been basically determined after the process plan is frozen.
Cost control means of BIW in stamping field
Figure 1 BIW cost composition
Stamping synchronous engineering is a synchronous integrated design implemented in the process of product development. Its main purpose is to identify product design and process design problems in advance, reduce product change cost and manufacturing risk, reduce product development cost and production cost, improve product quality and shorten development cycle. Its work runs through the whole process of product development. According to the different stages of product development, the focus of work is different. In the stage of product design, the feasibility analysis report of stamping process is mainly prepared from the stamping formability and fed back to the product R & D department. In the stamping design stage, it is mainly to work out the feasible stamping process, the specific number of working procedures and the stamping direction and work content of each process. In the process validation stage, the process plan is verified and re optimized, and the corresponding evaluation, correction and continuous improvement are carried out.
Stamping cost control planning
Stamping cost control should be planned in advance and run through the whole product development process. From the whole vehicle to the sub assembly to the parts, we can refer to the current situation of similar historical vehicles. After removing the unreasonable factors, we can set a reference value. Then, combined with CAE analysis, we can give the standard value and challenge value, and work together with tooling manufacturers to achieve the cost target. Objective planning can be carried out in each stage of “modeling design product design process design process verification”, the results are summarized, confirmed and improvement measures are taken to ensure that the optimal product is designed, the best process is selected and the strictest verification is controlled, and the cost reduction work is implemented in each stage of project operation. At the same time, summarize and refine the excellent scheme and experience in each stage, and convert them into various design guidelines to guide the development of subsequent projects. The cost control measures and effects of each stage are shown in Table 1.
Improve the utilization rate of vehicle materials
Material utilization is directly related to the cost of BIW. Taking a certain vehicle model as an example, the material utilization rate of the whole vehicle is increased by 1 percentage point, and the sheet weight is saved about 12.32 kg. According to the reference price of sheet metal market of 6 yuan / kg, the cost of BIW is saved by 12.32 kg × 6 yuan / kg = 73.92 yuan. The improvement of material utilization can be carried out in the stages of modeling, product design, process analysis and design, and trial production. Figure 2 shows how to improve the material utilization rate of a certain car in the design stage by means of product boundary optimization, splitting and assembling, etc In the process design stage, through optimizing process supplement, optimizing layout, swing shear, developing side discharge blanking die, mold closing, laser tailor welding, parts nested punching, waste utilization and other process means, the vehicle material utilization rate is increased from 55.07% of the original plan to 58.17% when the scheme is frozen. The challenge goal is achieved. In the process validation stage, the material utilization rate of the whole vehicle was further improved by reducing the size of material pieces. The non skylight version reached 59.14%, the small skylight version 58.59%, and the panoramic skylight version 58.29%.