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

    Reducing forming tonnage and process number of stamping parts
    The production cost of stamping parts is directly related to the selection of press tonnage and the number of working procedures. The larger the tonnage of the machine tool selected in the process design of stamping die, the more production processes, the higher the production cost. Reasonable selection and optimization of stamping equipment model and reduction of process number can reduce production cost. For example, the design tonnage of stamping machine tools in our company generally uses CAE theoretical tonnage multiplied by empirical coefficient and selects forming tonnage by referring to historical vehicle models. The forming R angle is enlarged through the forming parts, the wave edge is used for repairing and punching dies, and the die lapping and non critical surface are avoided. The physical verification and optimization of the on-site tonnage can reduce the forming tonnage.
    The process ratio (number of molds / parts) of the whole vehicle can reflect the production cost of the whole vehicle to a certain extent. Generally, the whole vehicle is controlled within 2.4. In the design stage, the complexity of the die can be reduced by optimizing the parts. The process ratio of parts can be reduced by using multi cavity mold, left and right mold closing, common mold, sleeve mold and so on. As shown in Figure 4.
    Reduce the investment cost of tooling development
    Figure 5 simple tooling scheme
    Figure 6 normal thickness range of automobile plate
    The development cost of stamping die accounts for the largest proportion of R & D investment, accounting for more than half, while the development of casting mold accounts for 80% of all mold development costs. The semi tooling scheme can be used for non key casting mold parts of the vehicle with small expected output. Only the forming die is developed, and the laser cutting scheme is used for the repair and stamping die. The repair and punching tooling can be developed after the vehicle is loaded. For the vehicle type which is determined not to develop full tooling, the one-time forming of parts can not consider the repair and punching angle, which can further reduce the development of the turning type die. The semi tooling scheme can generally save 35% – 70% of the tooling cost. However, the production cost of laser cutting will increase correspondingly, and the break even point of our semi tooling scheme is about 10000 sets. If the life cycle is more than 10000 but not the main sales vehicle, the cost of tooling development can be reduced by reducing the design standards, such as reducing the template thickness, reducing the requirements of insert material and standard parts, developing simple mold, etc., which can reduce the tooling development investment cost, that is to say, reduce the tooling allocation and stamping parts cost. The simple tooling scheme is shown in Figure 5
    Optimization of parts selection
    Part material selection optimization is also one of the technical cost reduction schemes. In the design stage, it is necessary to strengthen the BOM material review of the car body, minimize the sheet metal specifications and special specifications, so as to facilitate centralized large-scale procurement and price negotiation. In addition, among the sheets of the same specification, generally 1.5mm thick plate is the cheapest, and the zinc iron alloy plate b340lad is cheaper than other materials. See Figure 6 for the normal thickness range of automobile plate. According to the market price information, the stamping material can be optimized without affecting the vehicle performance and the part formability. At the same time, it can increase the application of new materials and new technologies. Laser tailor welded blanks and hot formed parts are relatively mature. Aluminum alloy and hydroforming parts are gradually researched and applied. The application of new technology can not only improve the strength of BIW, but also effectively reduce the cost.
    As the most important stage to control the cost of BIW, the process planning before the freezing of product design will determine the subsequent tooling cost and production cost. Therefore, it is necessary to carry out cost control activities from the product process, equipment rationality and tooling development lean. Everything is done in advance, and if not, it will be abandoned. The cost control of stamping parts can be implemented in the product design stage with large space and high contribution. It can be continuously improved through system planning, design improvement, process optimization, process confirmation, evaluation and correction through comparison of large database of historical vehicle models.