Plastic Injection Tools

Analysis of SMC Mould Manufacturing Technology

Analysis of SMC Mould Manufacturing Technology

  • 2021-11-15
The rapid development of mold manufacturing technology has become an important part of modern manufacturing technology. Such as the CAD/CAM technology of the mold, the laser rapid prototyping technology of the mold, the precision forming technology of the mold, the ultra-precision processing technology of the mold, and the finite element method and the boundary element method are used for the dynamics of the flow, cooling and heat transfer process in the mold design. Simulation technology, 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.

01 High-speed milling: the third generation of mold making technology

High-speed milling processing not only has high processing speed and good processing accuracy and surface quality, but also has low temperature rise compared with traditional cutting processing (the workpiece is only increased by 3℃), and the thermal deformation is small, so it is suitable for temperature and thermal deformation Sensitive materials (such as magnesium alloy, etc.) are processed; because of the small cutting force, it can be applied to the processing of thin-walled and poorly rigid parts; the 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, and has become the third generation of mold making technology.

02 EDM milling and "green" product technology

From the 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, the new trend in foreign countries is to carry out EDM machining technology (Electric Discharge Generating Processing Technology) The research and development of this is a new technology that replaces the traditional molding electrode processing cavity. It uses high-speed rotating simple tubular electrodes for three-dimensional or two-dimensional contour processing (like CNC milling), so manufacturing is no longer required Complex forming electrodes, this is obviously a major development in the field of EDM machining.

Recently, Japan's Mitsubishi Corporation launched the EDSCAN8E EDM machine tool and has made new progress. This machine can automatically compensate for electrode loss. The dedicated CAM system developed for this machine on Windows 95 can be linked with general CAD such as AutoCAD, and can perform online precision measurement to ensure high-precision machining. In order to confirm whether the processed shape is abnormal or incomplete, the CAM system can also realize simulation processing.

With the advancement of EDM technology, people pay more and more attention to the safety and protection technology of EDM, and many EDM machine tools 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. At the same time, the international market is paying more and more attention to the requirements of safety protection technology.

At present, the main problem of EDM machine tools is radiation harassment, because it has a greater impact on safety and environmental protection. As the international market pays more and more attention to "green" products, EDM machine tools are the leading equipment for mold processing. "Green" product technology will be a problem that must be solved in the future.

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

At present, the mold software developed by Britain, the United States, Germany and other countries and some universities and research institutes in my country has the characteristics of intelligence, integration and mold manufacturability evaluation of a new generation of mold CAD/CAM software.

The 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 the engineering knowledge base in a specific form and can be easily called by the mold. With the support of intelligent software, mold CAD is no longer an imitation of traditional design and calculation methods, but under the guidance of advanced design theories, full use of the rich knowledge and successful experience of experts in the field, the design results must be reasonable Sexuality and advancement.

The new generation of mold software uses three-dimensional ideas and intuitive feelings to design mold structures. The generated three-dimensional structure information can be conveniently used for mold manufacturability evaluation and CNC machining. This requires mold software to perform three-dimensional parameterized feature modeling and molding. Process simulation, CNC machining process simulation, information exchange, organization and management have reached a fairly complete level and have a high level of integration. To measure the degree of software integration, it depends not only on whether the functional modules are complete, but also whether these functional modules share the same data model, and whether they form a global dynamic database in a unified manner to achieve comprehensive management and sharing of information to support mold design The whole process of manufacturing, assembly, inspection, testing and production.

The mold manufacturability evaluation function plays an important role in the new generation of mold software. It is not only necessary to screen multiple options, but also to evaluate the rationality and economy of the mold design process, and provide a basis for mold designers to modify.

In the new generation of mold software, manufacturability evaluation mainly includes evaluation of mold design and manufacturing costs, evaluation of mold assemblability, evaluation of mold parts manufacturing processability, evaluation of mold structure and forming performance, etc.  The new generation of software should also have assembly-oriented functions, because the function of the mold can only be reflected through its assembly structure. After adopting the assembly-oriented design method, mold assembly is no longer a simple assembly of parts one by one. Its data structure can not only describe the function of the mold, but also define the assembly characteristics of the relationship between the mold parts, and realize the association of the parts. Can effectively ensure the quality of the mold.

04. Advanced rapid mold manufacturing technology

1. The rapid development of laser rapid prototyping (RPM) technology has reached the international level and has gradually realized commercialization. The world’s commercialized rapid prototyping processes mainly include SLA (stereolithography), LOM (layered split manufacturing), SLS (selective laser sintering), and 3D-P (three-dimensional printing).

Tsinghua University was the first to introduce SLA250 (stereolithography or photosensitive resin laser curing) equipment and technology from 3D in the United States and conduct development and research. Functional rapid prototyping manufacturing system" (with layered entity manufacturing-SSM, melt-extrusion molding-MEM), this is the world's only system with two types of rapid prototyping processes (national patent) with independent intellectual property rights in my country, and has good performance 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. The dieless multi-point forming system uses CAD/CAM/CAT technology as the main method, which is fast and economical. Realize the automatic forming of three-dimensional curved surface. Jilin University of Technology has undertaken national key scientific and technological research projects related to dieless forming, and has independently designed and manufactured dieless multi-point forming equipment with an internationally 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 our country is in a leading position in theoretical research and practical application, and is currently developing towards popularization and application.

3. The resin stamping die was successfully used in the trial production of domestic cars for the first time. FAW Mould Manufacturing Co., Ltd. designed and manufactured 12 sets of resin molds for the trial production of the new Xiaohongqi car. The 12 sets of molds are the drawing molds for large and complex interior and exterior covering parts such as the trunk, the hood, the front and rear fenders, etc. , Its main feature is that the mold surface is based on the main model processed by CAD/CAM, and it is formed by high-strength resin refined by Swiss Ciba. The gap between the convex and concave molds is accurately controlled by imported special wax pieces, and the dimensional accuracy of the mold is high. The cycle time can be shortened by one-half to two-thirds, and the manufacturing cost can be saved about 10 million yuan (12 sets of molds). It has opened up a new way for the trial production and small batch production of cars in my country, which is the first in China. Swiss Ciba Fine Chemicals experts believe that it can reach the international level in the 1990s.

05. On-site mold inspection technology

With the development of precision molds, the requirements for measurement are getting higher and higher. The precision three-coordinate measuring machine has been restricted by the environment for a long time and is rarely used in the production site. The 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 the workshop to realize the characteristics of measuring on-site .

06. Mirror polished mold surface engineering technology

Mold polishing technology is an important part of mold surface engineering and an important process for post-processing in the mold manufacturing process. At present, the domestic mold polishing equipment, abrasives and processes that can be polished to Ra0.05μm can basically meet the needs, but the mirror polishing equipment, abrasives and processes that need to be polished to Ra0.025μm are still in the exploratory stage. With the 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 the mold surface polishing is not only affected by the polishing equipment and process technology, but also by the mirror finish of the mold material. This has not attracted enough attention, that is, the polishing itself is restricted by the 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 by the naked eye. If it continues to be thrown, it can only increase the brightness, but the roughness is hopeless. Therefore, the domestic production of mirror molds Imported mold materials are often used, such as Sweden's ASSAB 136, Japan's Datong PD555, etc., to obtain satisfactory mirror finish.

Mirror mold material is not only a problem of chemical composition, but more importantly, a series of advanced processes such as vacuum degassing, argon protection ingot, vertical continuous casting and rolling, and soft forging are required during smelting, so that there are fewer internal defects in the mirror mold steel. A series of advantages, such as fine particle size of impurities, high degree of dispersion, fine metal grain size, and good uniformity, can meet the requirements of mold steel polished to mirror surface.

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