What is main mold design, do you know?

Time:2020-09-14 09:11:12 / Popularity: / Source:

Rapid development of mold manufacturing technology has become an important part of modern manufacturing technology. Such as CAD/CAM technology of mold, laser rapid prototyping technology of mold, precision forming technology of mold, ultra-precision processing technology of mold, dynamic simulation technology of flow, cooling, and heat transfer process using finite element method and boundary element method in mold design, mold CIMS technology, mold DNM technology and numerical control technology that have been developed cover almost all modern manufacturing technologies.
Modern mold manufacturing technology is developing in the direction of accelerating information drive, improving manufacturing flexibility, agile manufacturing and system integration.

1. High-speed milling: third generation of mold making technology

mold manufacturing technology 
High-speed milling processing not only has high processing speed, good processing accuracy and surface quality, but also has low temperature rise compared with traditional cutting processing (workpiece is only raised by 3℃), thermal deformation is small, so it is suitable for processing of temperature and thermal deformation sensitive materials (such as magnesium alloy, etc.). Also due to small cutting force, it can be applied to the processing of thin-walled and poorly rigid parts; reasonable selection of tools and cutting parameters can achieve a series of advantages such as hard materials (HRC60) processing. Therefore, high-speed milling processing technology is still a hot topic at present, and it has developed in the direction of higher agility, intelligence, and integration, becoming third generation of mold making technology.

2. EDM milling and "green" product technology

From perspective of foreign EDM machine tools, whether in terms of performance, process indicators, intelligence, and automation, they have reached a very high level. At present, new trend in foreign countries is research and development of electric discharge milling processing technology (electric discharge creation processing technology), which is a new technology that replaces traditional molding electrode processing cavity. It uses high-speed rotating simple tubular electrodes for three-dimensional or two-dimensional contour machining (like CNC milling), so there is no need to manufacture complex shaped electrodes. This is obviously a major development in the field of EDM machining.
Recently, Japan's Mitsubishi Corporation has launched EDSCAN8E EDM machine tool and has made new progress. This machine can automatically compensate for electrode loss. Dedicated CAM system developed for this machine on Windows 95 can be linked with general-purpose CAD such as AutoCAD, and can perform online precision measurement to ensure high-precision machining. In order to confirm whether processed shape is abnormal or incomplete, CAM system can also realize simulation processing.
With advancement of EDM technology, safety and protection technology of EDM has attracted more and more attention. Many EDM machine tools have considered safety protection technology. At present, European Community has stipulated that machine tools without "CE" mark cannot enter European Community market, international market is also paying more and more attention to requirements of safety protection technology. 
At present, main problem of EDM machine tools is radiation harassment, because it has a greater impact on safety and environmental protection. As international market pays more and more attention to "green" products, EDM machine tools are leading equipment for mold processing. "Green" product technology will be a problem that must be solved in the future.

3. A new generation of mold CAD/CAM software technology

At present, mold software developed by some universities and research institutes in Britain, United States, Germany and my country has characteristics of intelligence, integration and mold manufacturability evaluation of the new generation of mold CAD/CAM software.
New generation of mold software should be based on a large amount of knowledge summarized from mold design practice. This knowledge has been systematically and scientifically sorted, stored in engineering knowledge base in a specific form and can be easily called by mold. With support of intelligent software, mold CAD is no longer an imitation of traditional design and calculation methods, but under guidance of advanced design theories, full use of rich knowledge and successful experience of experts in the field, its design results must be reasonable and advanced.
New generation of mold software designs mold structures with three-dimensional ideas and intuitive feelings. Generated three-dimensional structure information can be conveniently used for mold manufacturability evaluation and CNC machining. This requires mold software to achieve a fairly complete level and a high level of integration in terms of three-dimensional parameterized feature modeling, molding process simulation, numerical control machining process simulation, information exchange, organization and management. To measure degree of software integration, it depends not only on whether functional modules are complete, but also whether these functional modules share same data model, whether they form a global dynamic database in a unified manner to achieve comprehensive management and sharing of information to support entire process of mold design, manufacturing, assembly, inspection, testing, and production.
Mold manufacturability evaluation function plays a very important role in new generation of mold software. It is necessary to screen multiple solutions, evaluate rationality and economics of mold design process, and provide a basis for mold designers to modify.
In new generation of mold software, manufacturability evaluation mainly includes evaluation of mold design and manufacturing costs, evaluation of mold assembly, evaluation of mold parts manufacturing processability, evaluation of mold structure and forming performance, etc.  New generation of software should also have assembly-oriented functions, because function of mold can only be reflected through its assembly structure. After assembly-oriented design method is adopted, mold assembly is no longer a simple assembly of parts one by one. Its data structure can not only describe function of mold, but also define assembly characteristics of relationship between mold parts, realize association of parts, so it can effectively guarantee quality of mold.

4. Advanced rapid mold manufacturing technology

1. With rapid development of laser rapid prototyping technology (RPM), my country has reached international level and is gradually realizing commercialization. World’s commercialized rapid prototyping processes mainly include SLA (stereolithography), LOM (layered split manufacturing), SLS (selective laser sintering), and 3D-P (three-dimensional printing).
mold manufacturing technology 
Tsinghua University was the first to introduce SLA250 (stereolithography or photosensitive resin laser curing) equipment and technology from 3D in United States, conduct development and research. After several years of hard work and several improvements, launched "M-RPMS-type Functional rapid prototyping manufacturing system" (with layered entity manufacturing-SSM, melt extrusion molding-MEM), this is the world's only system with two kinds of rapid prototyping processes (national patent) with independent intellectual property rights in my country, and has good performance-to-price ratio.
2. Dieless multi-point forming technology is another advanced manufacturing technology that uses height-adjustable punch groups to replace traditional molds for sheet surface forming. Dieless multi-point forming system uses CAD/CAM/CAT technology as main method to quickly and economically realize automatic forming of three-dimensional curved surface. Jilin University of Technology has undertaken national key scientific and technological research projects related to dieless forming, has independently designed and manufactured dieless multi-point forming equipment with international leading level.
Compared with Massachusetts Institute of Technology in United States, University of Tokyo in Japan, and Tokyo Institute of Technology in Japan, this technology in my country is in a leading position in both theoretical research and practical application, is currently developing towards popularization and application.
3. Resin stamping die was successfully used in trial production of domestic cars for the first time. FAW Mould Manufacturing Co., Ltd. designed and manufactured 12 sets of resin molds for modified trial production of new Xiaohongqi car. These 12 sets of molds are drawing molds for large, complex interior and exterior covering parts such as trunk, hood, front and rear fenders, etc. Its main feature is that mold surface is based on main model processed by CAD/CAM, and is molded by high-strength resin refined by Swiss Ciba. Gap between convex and concave molds is accurately controlled by imported special wax pieces, dimensional accuracy of mold is high. Cycle can be shortened by one-half to two-thirds, and manufacturing cost can be saved about 10 million yuan (12 sets of molds). It has opened up a new way for trial production and small batch production of cars in my country, which is the first in China. Swiss Ciba Fine Chemical experts believe that it can reach international level in the 1990s.

5. On-site mold inspection technology

On-site mold inspection technology 
With development of precision molds, requirements for measurement are getting higher and higher. Precision three-coordinate measuring machine has been restricted by environment for a long time and is rarely used in production site. New generation of three-coordinate measuring machines basically have temperature compensation and adopt anti-vibration materials, improve dust-proof measures, improve environmental adaptability and use reliability, so that they can be easily installed in workshop to realize characteristics of measuring on-site .

6. Mirror polished mold surface engineering technology

Mold polishing technology 
Mold polishing technology is an important part of mold surface engineering and an important process of post-processing in mold manufacturing process. At present, domestic mold polishing equipment, abrasives and processes that can be polished to Ra0.05μm can basically meet needs, but mirror polishing equipment, abrasives and processes that need to be polished to Ra0.025μm are still in exploration stage. With large-scale application of mirror injection molds in production, mold polishing technology has become a key issue in mold production. As there are still certain problems in domestic polishing technology and materials, a large part of injection molds such as point-and-shoot camera lens injection molds, CD, VCD discs and tools with high transparency requirements still rely on imports.
It is worth noting that mold surface polishing is not only affected by polishing equipment and process technology, but also by mirror finish of mold material. This has not attracted enough attention, that is, polishing itself is restricted by mold material. For example, when 45# carbon steel is used as an injection mold, when it is polished to Ra0.2μm, obvious defects can be seen with naked eye. If it continues to be polished, it can only increase brightness, and roughness is hopeless. Therefore, imported mold materials are often used in the production of mirror molds in China. For example, ASSAB 136 from Sweden and PD555 from Datong of Japan can obtain satisfactory mirror surface.
Mirror mold material is not only a problem of chemical composition, but more importantly, a series of advanced technologies such as vacuum degassing, argon protection ingot, vertical continuous casting and rolling, and soft forging are required during smelting, so that mirror mold steel has a series of advantages such as less internal defects, fine particle size of impurities, high degree of dispersion, fine metal grain size, and good uniformity to meet requirements of mold steel polished to mirror surface.

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