Mold is the basic technological equipment in auto industry. More than 90 percent of auto parts are formed by mold. Manufacturing an auto needs 1,500 molds, among that needs about 1,000 stamping molds. In development of new models, 90% of workloads are carried out on the modification of car body. In development cost of new models, about 60% of costs are used to develop body, stamping technology and equipment. In the costs of the whole auto manufacturing, about 40% of costs are body stamping parts and the costs of assembling.
In the development of auto mold, molding technology has shown the following tendencies:
1. The functions of CAE are more prominent.
In recent years, with the software and hardware highly developing, CAE is more and more important. In developed countries such as the U.S., Japan and Germany, CAE has become an important links, widely used for predicting forming defects, optimizing stamping technologies and mold structure, highly improving the reliability of mold designing and reducing the time of mold test. In China, large numbers of auto mold manufacturers also make a great progress and receive good effects. The application of CAE saves the costs of mold test significantly, reducing development cycle of stamping mold. CAE has already become a measure for ensuring the quality of mold. CAE gradually transfers mold design from empirical design to scientific design.
2. Three-dimension design of mold is solidified.
Three-dimension of mold is the key of digital mold technology, the base of realizing the integration of design, manufacturing and test. Toyota and General Motors have already used three-dimension design of mold and gained good effects. Besides advantageous for realizing integrated manufacturing, three-dimension design of mold is convenient for interference inspection so that analysis of movement interferences can be carried out.
3. Digital mold technology has already become the mainstream.
In recent years, digital mold technology highly developed is an efficient path for figuring out the problems faced with by auto mold development. Digital mold technology refers to that use CAX in the design and manufacturing of mold. Digital auto mold technology mainly includes the following aspects:
(1) Designing for fabrication (DFM): manufacturability is considered and analyzed during design, ensuring the success of technology;
(2) Assistive technology for design of molded surface: develop intelligent surface design technology;
(3) CAE is used to analyze and simulate process of stamping, predicting and figuring out defects or forming problems which may occur.
(4) Use three-dimension structure to instead of traditional two-dimension design.
(5) Use CAPP, CAM and CAT in the manufacturing process of mold.
(6) Under the guidance of digital technology, deal with the problems during mold test and stamping.
4. Automation of mold processing develops rapidly.
The advanced processing technology and equipment are important bases for improving productivity and ensuring the quality of products. Advanced auto mold manufacturers should be equipped with numerical control machine tools having double workbenches, automatic tool changer (ATC), automatic optical current control system and online measuring system for work pieces. Numerical control machining has already been developed from single molded surface machining to comprehensive machining of molded surface and structural surface, from low speed processing to high speed processing. Automatic processing technology is highly developed.
5. Stamping technology of high strength steel sheet is the future development direction.
For excellent properties of yield ratio, strain hardening, strain distribution and collision energy absorption, high strength steel sheet is constantly used for auto. At present, high strength steel sheet used for
auto stamping parts mainly includes hardening steel (BH steel), dual-phase steel (DP steel) and transformation induced plasticity steel (TRIP steel), etc. Soft steel based on IF steel which are widely used currently will be replaced by high strength steel sheet, high strength low alloy steel taken place of by dual-phase steel and super strength steel sheet. Now, high strength steel sheet used for auto parts in China is still limited at structural components and beam parts. Tensile strength of used steel is below than 500MPa.
6. New mold products are marketed timely.
With auto stamping developing into high effect and automation, the application of progressive die in the manufacturing of auto stamping parts will be wider. Completed stamping parts particularly some small complicated stamping parts which need amount of stamping mold to stamp step by step based on traditional techniques more and more adopt progressive die. Progressive die is a new kind of high-tech mold product, having high technical impediment, high manufacturing precision and long production cycle.
7. Materials of mold and surface treatment will be paid more attention.
The quality and performance of mold materials is an important factor having influence on quality, service and cost of mold. In recent years, besides die steel having high tenacity and high abrasive resistance, manufactured by flame hardening and powder metallurgy, cast iron is also used for large stamping mold which is notable developing tendency. Nodular cast iron has good toughness and abrasive resistance, welding property, workability and surface quenching performance. The cost is also lower than alloy cast iron. So, it is widely used for auto stamping molds.
8. Scientization and informatization of management are development direction of mold enterprise.
The other important aspect of auto molding technology development is scientization and informatization of management. Scientization of management promotes mold enterprises to constantly develop into just-in-time manufacturing and lean production. The management of enterprise will be more precise; production efficiency is highly improved; invalid organization, links and personnels are simplified constantly. With modern management technology advancing, large numbers of advanced informational management tools including enterprise resources planning system (ERP), custom relation management (CRM), supply chain management (SCM) and project management (PM) have already widely been applied in mold enterprises.
9. Fine manufacturing is an inevitable trend
Fine manufacturing is for development process and the results of mold. It is shown that rationalization of stamping techniques and the design of mold structure, high precision of mold processing, high reliability of mold products and rigor of technical management. Fine manufacturing is not just a single technology while it is concentrated expression of design, processing and management technology. The realizing of fine manufacturing depends on rigorous management, besides perfection on technology.
