The rapid development of mold manufacturing technology has become an important component of modern manufacturing technology. Such as mold CAD/CAM technology, mold laser rapid prototyping technology, mold precision forming technology, mold ultra precision machining technology, mold design using finite element method and boundary element method for dynamic simulation of flow, cooling, and heat transfer processes, mold CIMS technology, developed mold DNM technology, and CNC technology, almost covering all modern manufacturing technologies.
Modern mold manufacturing technology is developing towards accelerating information driven, improving manufacturing flexibility, agile manufacturing, and systematic integration.
1、 High speed milling: third-generation mold making technology
High speed milling not only has high processing speed and good surface quality, but also has lower temperature rise (only 3 ℃ increase in workpiece processing) and smaller thermal deformation compared to traditional cutting, making it suitable for processing temperature sensitive materials such as magnesium alloys; Due to its low cutting force, it is suitable for machining thin-walled and poorly rigid parts; Reasonable selection of cutting tools can achieve a series of advantages such as machining hard materials (HRC60). Therefore, high-speed milling technology is still a hot topic at present, and it has developed towards higher sensitivity, intelligence, and integration, becoming the third generation of mold making technology.
2、 Electric discharge milling "green" product technology
From the perspective of foreign electrical machining machines, they have reached a considerable level in terms of performance, process indicators, intelligence, and automation. Currently, there is a new trend in research and development of electrical discharge milling technology (electrical discharge generative machining technology) in foreign countries. This new technology replaces the traditional use of shaped electrodes to machine cavities. It uses high-speed rotating simple tubular electrodes for three-dimensional or two-dimensional contour machining (like CNC milling), so there is no longer a need to manufacture complex shaped electrodes. This is clearly a significant development in the field of electrical discharge machining.
With the advancement of electrical discharge machining technology, the safety protection technology of electrical discharge machining is increasingly valued by people, and many electrical machining machines have considered safety protection technology. At present, the European Community has stipulated that machine tools without the "CE" mark cannot enter the European Community market, and the international market is increasingly emphasizing safety and protection technology requirements.
At present, the main problem with electric discharge machining (EDM) machine tools is radiation disturbance, as it has a significant impact on safety and environmental protection. In the international market, there is an increasing emphasis on "green" products. As the leading equipment for mold processing, EDM machine tools must solve the problem of "green" product technology in the future.
3、 New generation CAD/CAM software technology for molds
At present, mold software developed by research institutes in countries such as the UK, US, Germany, and some higher education institutions in China has the characteristics of intelligent, integrated, and manufacturability evaluation of new generation mold CAD/CAM software.
The new generation of mold software should be based on summarizing a large amount of knowledge from mold design practice. These knowledge have been systematically and scientifically organized, stored in a specific form as an engineering knowledge base, and can be easily accessed by molds. With the support of intelligent software, mold CAD will no longer imitate the traditional design and calculation methods, but under the guidance of advanced design theory, fully use the rich knowledge and successful experience of experts in this field, and the design results will be reasonable and progressiveness.
The new generation of mold software designs mold structures with three-dimensional thinking and intuitive feeling, and the generated three-dimensional structural information can be easily used for evaluating the manufacturability of molds in CNC machining. This requires mold software to achieve a considerable degree of completeness and integration in three-dimensional parametric feature modeling, molding process simulation, CNC machining process simulation, and information exchange organization and management. To measure the degree of software integration, it is not only necessary to consider whether the functional modules are complete, but also whether these functional modules share the same data model and form a global dynamic database in a unified manner to achieve comprehensive information management and sharing, in order to support the entire process of mold design, manufacturing, assembly, inspection, testing, and production.
The evaluation function of mold manufacturability is very important for the new generation of mold software. It not only screens multiple solutions, but also evaluates the rationality and economy of the mold design process, and provides modification basis for mold designers.
The manufacturability evaluation of the new generation of mold software mainly includes mold design and manufacturing cost estimation, mold assemblability evaluation, mold part manufacturing process evaluation, mold structure and forming performance evaluation, etc. The new generation of software should also have assembly oriented functionality, as mold functionality can only be reflected through its assembly structure. After adopting the assembly oriented design method, mold assembly is no longer simply assembled one by one. Its data structure can describe the functions of the mold and define the assembly characteristics of the interrelationships between mold components, achieving component correlation and effectively ensuring mold quality.
4、 Advanced Rapid Mold Manufacturing Technology
1. The development of laser rapid prototyping technology (RPM) is advancing rapidly, and China has reached the international level and gradually achieved commercialization. The commercially available rapid prototyping processes in the world mainly include SLA (stereolithography), LOM (layered manufacturing), SLS (selective laser sintering), and 3D-P (three-dimensional printing).
Tsinghua University was the first to introduce the SLA250 (stereolithography or photosensitive resin laser curing) equipment and technology from the American 3D company and conduct research and development. After several years of hard work and multiple improvements, it has perfected and launched the "M-RPMS type multifunctional rapid prototyping manufacturing system" (with layered solid manufacturing SSM and melt extrusion molding MEM), which is the only one in the world with independent intellectual property rights in China to have two rapid prototyping process systems (national patents) and has a good cost performance ratio.
2. The mold free multi-point forming technology uses a highly adjustable punch group instead of traditional molds for sheet metal surface forming, which is another advanced manufacturing technology. The mold free multi-point forming system mainly uses CAD/CAM/CAT technology to quickly and economically achieve automatic 3D surface forming. Jilin University of Technology has undertaken the national key scientific and technological research project on mold free forming, and has independently designed and manufactured mold free multi-point forming equipment with international leading level.
Compared with the Massachusetts Institute of Technology in the United States, the University of Tokyo in Japan, and the Tokyo Institute of Technology in Japan, this technology in China is in a leading position in theoretical research and practical application, and is currently developing towards promotion and application.
3. The first domestically produced sedan trial production of resin stamping molds has been successfully applied. FAW Mold Manufacturing Co., Ltd. has designed and manufactured 12 sets of resin molds for the modified trial production of the all-new Xiaohongqi sedan. These 12 sets of molds include large and complex inner and outer cover stretching molds for the luggage compartment, engine hood, front, rear, left and right fenders, etc. The main features of the molds are that the mold surface is based on the CAD/CAM processing main model, and Swiss Ciba refined high-strength resin casting is used for forming. The clearance between the convex and concave molds is accurately controlled by imported special wax sheets, and the mold size accuracy is high. The manufacturing cycle can be shortened by half to two-thirds, and the manufacturing cost can be saved by about 10 million yuan (12 sets of molds). This has opened up a new path for small-scale production of sedans in China, which is the first of its kind in the country. Experts from Swiss Ciba Specialty Chemicals believe that it can reach the international level of the 1990s.
5、 On site mold inspection technology
The development of precision molds requires increasingly high measurement standards. Precision coordinate measuring machines have been rarely used on production sites due to environmental limitations for a long time. The new generation of coordinate measuring machines basically have temperature compensation and use anti vibration materials, improve dust prevention measures, enhance environmental adaptability and reliability, making them easy to install and use in workshops to achieve on-site measurement characteristics.
6、 Mirror polishing mold surface engineering technology
Mold polishing technology is an important component of mold surface engineering and an important process for post-treatment during mold manufacturing. At present, domestic mold polishing equipment, grinding tools, abrasives, and processes for Ra0.05 μ m polishing can basically meet the needs, while equipment, grinding tools, abrasives, and processes for Ra0.025 μ m mirror polishing are still in the exploratory stage. With the large-scale application of mirror injection mold production, mold polishing technology has become a key issue in mold production. Due to certain issues in domestic polishing technology and materials, there is still a significant reliance on imports for injection molds with high transparency requirements, such as those for point and shoot camera lenses, CDs, VCDs, and tools.
It is worth noting that the surface polishing of molds is not only affected by the polishing equipment technology, but also by the mirror finish of the mold material. This has not been given enough attention, which means that polishing itself is constrained by the mold material. For example, when using 45 # carbon steel as an injection mold and polishing it to Ra0.2 μ m, obvious defects are visible to the naked eye. Continuing to polish can only increase brightness, and there is no hope of improving roughness. Therefore, currently, imported mold materials are often used in domestic mirror mold production, such as Sweden's Yishengbai 136 and Japan's Datong PD555, which can achieve satisfactory mirror finish.
Mirror mold materials not only have chemical composition issues, but also require a series of advanced processes during smelting, such as vacuum degassing, argon protection for ingots, vertical continuous casting and rolling, and flexible forging, to reduce internal defects, fine impurity particle size, high dispersion, fine metal grain size, and good uniformity of mirror mold steel, in order to achieve the requirements of polishing to mirror mold steel.
