Table of Contents
The level of mold production technology has become an important indicator of a country’s product manufacturing level because molds largely determine the quality, efficiency, and new product development capabilities of products. With China’s entry into the WTO, the development of China’s mold industry will face new opportunities and challenges.
The development of China’s mold industry has received increasing attention and concern. “Molds are the basic process equipment for industrial production” has also reached a consensus. In products such as electronics, automobiles, motors, electrical appliances, instruments, meters, home appliances, and communications, 60% to 80% of the parts rely on mold forming (molding). The high precision, high complexity, high consistency, high productivity, and low consumption of mold-made parts are unmatched by other processing and manufacturing methods. Molds are also “benefit amplifiers”. The value of the final product produced by molds is often dozens or hundreds of times the value of the mold itself. At present, the annual output value of molds in the world is about 60 billion US dollars, and the output value of the mold industry in industrially developed countries such as Japan and the United States has exceeded that of the machine tool industry.
The current status of China’s mold technology
1. Dies
With large-scale cover die as a representative, China has been able to produce some car cover die. The design and manufacturing of car cover dies is difficult, and the quality and precision requirements are high, which represents the level of cover die. In terms of design and manufacturing methods and means, it has reached the international level, and the mold structure and function are also close to the international level, which is a big step forward in the process of localization of car molds.
However, there is still a certain gap compared with other countries in terms of manufacturing quality, precision, manufacturing cycle, and cost. Multi-position progressive dies and multi-functional molds, which represent the advanced level of die technology, are the precision mold varieties that my country focuses on developing. In terms of manufacturing precision, service life, mold structure, and function, there is still a certain gap compared with foreign multi-position progressive dies and multi-functional molds.
2. Plastic molds
In recent years, China’s plastic molds have made great progress. In terms of large plastic molds, it has been able to produce 34-inch large-screen color TV plastic shell molds, a 6kg large-capacity washing machine full set of plastic molds automobile bumpers integral instrument panels, and other plastic molds. In terms of precision plastic molds, we can produce multi-cavity small-module gear molds and 600-cavity plastic sealing molds, as well as 1-mold 2-cavity aviation cup molds with a thickness of only 0.08mm and difficult plastic door and window extrusion.
Internal or external hot runner devices are adopted, and a few units have adopted highly difficult needle valve hot runner molds with world-leading levels, which eliminates the gate marks of the parts. Gas-assisted injection technology has been successfully applied. In terms of precision, the manufacturing precision of plastic model cavities can reach 0.02~0.05mm (0.005~0.01mm abroad), the contact gap of the parting surface is 0.02mm, the elastic deformation of the template is 0.05mm, the surface roughness value of the mold surface is Ra0.2~0.25um, the life of the plastic mold has reached 1 million times (3 million times abroad), and the mold manufacturing cycle is still 2~4 times longer than that of foreign countries. These parameters that indicate the overall level of molds are still far behind those of foreign countries.
3. Die-casting molds.
The rapid development of the automobile and motorcycle industries has promoted the development of die-casting mold technology. China is now able to produce aluminum alloy casting molds such as automobile engine cylinder covers, cover plates, transmission housings, motorcycle engine cylinders, gearbox housings, brakes, wheels, and escalator step die-casting molds. The technical level has improved, making most of the aluminum alloy die-casting molds for automobiles and motorcycles domestically produced.
When designing the mold, pay attention to solving the problem of thermal balance, reasonably determine the pouring system and cooling system, and adopt hydraulic core pulling and secondary pressurization structures according to manufacturing requirements. The overall level has been greatly improved. The manufacturing accuracy of the die-casting mold can reach 0.02~0.05mm (0.01~0.03mm abroad), the surface roughness of the cavity is Ra0.4~0.2wm (Ra0.02~0.01μm abroad), and the mold manufacturing cycle is 3~4 months for small and medium-sized molds, 4~8 months for medium-complex molds, and 8~12 months for large molds, which is about twice that of foreign countries. Mold life: Aluminum alloy casting molds generally last 40,000 to 80,000 times, and some can exceed 100,000 times. In foreign countries, it can reach 80,000 to 150,000 times or more.
4. Mold CAD/CAE/CAM technology
Mold CAD/CAE/CAM technology is a key technology for transforming traditional mold production methods. It can significantly shorten mold design and manufacturing cycles, reduce production costs, and improve product quality. It enables technicians to design and optimize products, mold structures, forming (molding) processes, CNC machining, and costs with the help of computers. Enterprises producing household appliances have successively introduced a considerable number of CAD/CAM systems, realized CAD/CAM integration, and used CAE technology to simulate the forming (molding) process. The use rate of CNC machining has also increased, achieving certain economic benefits, and promoting the development of China’s mold CAD/CAE/CAM technology.
In recent years, China has developed the CAD/CAM system for punching and cutting dies of Shanghai Jiaotong University, the CAXA series software of Beijing Beihang Haier Software Co., Ltd., and the stamping CAD/CAE/CAM system of Jilin Jinmesh Die Engineering Research Center, which have created good conditions for further popularizing die CAD/CAM technology. At present, the software development of computer-aided technology in China is still at a low level and requires the accumulation of knowledge and experience.
5. Standard parts of molds
Standard parts of molds can play a great role in shortening the mold manufacturing cycle, improving quality, and reducing costs. Therefore, standard parts of molds are increasingly widely used. Standard parts of molds mainly include cold stamping die frames, plastic die frames, push rods, and springs. New elastic components such as nitrogen springs have also been promoted and applied.
6. Mold materials and heat treatment
The quality, performance, variety, and timely supply of mold materials have a direct and significant impact on the quality, service life, and economic benefits of the mold. In recent years, some mold steel manufacturers in China have successively built and introduced some advanced process equipment, which has improved the unreasonable specifications of domestic mold steel varieties and specifications, and greatly improved the quality of mold steel. However, domestic mold steel varieties are incomplete and not in series. There are still many problems to be solved, such as multiple varieties, refined materials, and finished products.
In addition, it is necessary to study the material series suitable for forming molds such as glass, ceramics, refractory bricks, and floor tiles. Mold heat treatment is a key link in whether the performance of mold steel can be fully guaranteed. Most domestic companies still use salt-melting furnaces or electric furnaces for heating when quenching molds. Due to the lax implementation of mold heat treatment processes, the treatment quality is not high and unstable, which directly affects the service life and quality of the mold. In recent years, vacuum heat treatment furnaces have begun to be widely used in mold manufacturing.
Development trend of mold technology
1. Mold CAD/CAE/CAM is developing towards integration, three-dimensionalization, intelligence, and networking
(1)Integration of mold software functions
The integration of mold software functions requires that the software functional modules are relatively complete, and at the same time, each functional module adopts the same data model to achieve comprehensive management and sharing of information, thereby supporting the entire process of mold design, manufacturing, assembly, inspection, testing and production management, and achieving the goal of achieving optimal benefits.
For example, the serialized software of the British Delcam company includes surface solid geometry modeling, complex shape engineering drawing, industrial design advanced rendering, plastic mold design expert system, complex shape CAM, artistic modeling and carving automatic programming system, reverse engineering system and complex shape online measurement system. Other software with a high degree of integration include Pro/E, UG CATIA, etc.
(2)Three-dimensional mold design, analysis, and manufacturing
Traditional two-dimensional mold structure design is increasingly incompatible with modern production and integrated technology requirements. The three-dimensional and paperless mold design, analysis, and manufacturing require a new generation of mold software to design molds in a three-dimensional and intuitive way. The three-dimensional digital model can be conveniently used for CAE analysis of product structure, mold manufacturability evaluation, CNC machining, forming process simulation, and information management and sharing. Software such as Pro/E, UG, and CATIA have the characteristics of parameterization, feature-based, and full correlation, making mold parallel engineering possible.
In addition, Cimatran’s Moldexpert, Delcam’s Ps-mold, and Hitachi Zosen’s Space-E/mold are all 3D professional injection mold design software that can perform interactive 3D cavity and core design, mold frame configuration, and typical structure design. Moldflow Advisers, a three-dimensional realistic flow simulation software from Australia’s Moldflow, has been widely praised and applied by users. The knowledge-based intelligent function for manufacturing is one of the important indicators to measure the advancement and practicality of mold software.
For example, Cimatron’s injection mold expert software can automatically generate parting lines and parting surfaces according to the demolding direction, generate cores and cavities corresponding to the product, realize full correlation of mold frame parts, automatically generate material lists and drilling tables for NC processing, and can perform intelligent processing parameter settings, processing result verification, etc.
(3)Networking trend of mold software application
With the globalization and internationalization of molds in enterprise competition, cooperation, production, and management, as well as the rapid development of computer software and hardware technology: the development trend of networked mold software applications is to promote CAD/CAE/
(4) Networking trend of mold software application
With the globalization and internationalization of molds in enterprise competition, cooperation, production, and management, as well as the rapid development of computer software and hardware technology: the development trend of networked mold software application is to promote CAD/CAE/CAM technology across regions, enterprises and institutes in the entire industry to achieve the reintegration of technical resources and make virtual design and agile manufacturing technology possible. The United States pointed out in its “21st Century Manufacturing Enterprise Strategy” that by 2006, the automotive industry will realize agile production/virtual engineering solutions and shorten the automobile development cycle from 40 months to 4 months.
2. Mold inspection and processing equipment develops towards precision, efficiency, and multi-function
(1)Molds develop towards precision, complexity, and large scale, and the requirements for inspection equipment are getting higher and higher. At present, domestic manufacturers use more high-precision three-coordinate measuring machines from Italy, the United States, Japan, and other countries, which have digital scanning functions. The whole process from measuring the physical object → establishing the mathematical model → outputting the engineering drawing → mold manufacturing has been realized, and the development and application of reverse engineering technology have been successfully realized.
(2) CNC EDM machine tools
Sodick of Japan uses linear motor servo drive AO325L and AO550LLS-WEDM, which have the advantages of fast drive response, high transmission and positioning accuracy, and small thermal deformation. NCEDM of Charmilles of Switzerland has P-E3 adaptive control, PCE energy control, and an automatic programming expert system. In addition, some EDMs also use mixed powder processing technology, micro-precision processing pulse power supply fuzzy control (FC), and other technologies.
(3) High-speed milling machine tools (HSM)
Milling is an important means of cavity mold processing. High-speed milling has many advantages such as low workpiece temperature rise, small cutting force, stable processing, good processing quality, high processing efficiency (5 to 10 times that of ordinary milling), and the ability to process hard materials (<60HRC). Therefore, it is increasingly valued in mold processing. HSM is mainly used for large and medium-sized mold processing, such as automotive cover molds, die-casting molds, large plastic molds, and other curved surface processing.
(4) Research and development of mold automatic processing system
With the rapid development of various new technologies, mold automatic processing systems have appeared abroad, which is also the long-term development goal of my country. The mold automatic processing system should have the following characteristics: a reasonable combination of multiple machine tools; equipped with accompanying positioning fixtures or positioning plates; a complete CNC library of machines and tools; a complete CNC flexible synchronization system; and a quality monitoring and control system.
3. Wide application of rapid and economical molding technology
Shortening the product development cycle is an effective means to win market competition. Compared with traditional mold processing technology, rapid and economical molding technology has the characteristics of a short molding cycle and low cost. Its accuracy and lifespan can meet production needs. It is a comprehensive economic benefit. Relatively significant mold manufacturing technology.
Rapid prototyping manufacturing (RPM) technology is a new technology that integrates precision machinery manufacturing, computer technology, NC technology, laser molding technology, and material science. It is one of the most advanced parts and mold molding methods currently. RPM technology can be used directly or indirectly in mold manufacturing and has the characteristics of advanced technology, low cost, short design and manufacturing cycle, and moderate precision. From the conceptual design of the mold to the completion of manufacturing, it is only 1/3 of the time required by traditional processing methods and about 1/4 of the cost.
Now is the era of multi-variety, low-volume production. By the next century, this production method will account for more than 75% of industrial production. – On the one hand, the service life of the products is short and the varieties are updated quickly. On the other hand, the patterns of the products change frequently, which requires the production cycle of the mold to be as fast as possible. Therefore, the development of rapid and economical molds has attracted more and more attention.
For example, develop simple molds made of various superplastic materials (epoxy, polyester, etc.) (or filled with metal powder, glass fiber, etc.), medium and low melting point alloy molds, spray molding molds, rapid electroforming molds, and ceramic precision molds. Rapid and economical molds such as casting molds, ceramic blister molds, stacked molds, and rapid prototyping molds will further develop. Quick-change mold bases, quick-change punches, etc. will also be increasingly developed. In addition, rapid mold changing devices and rapid mold trial technology using computer control and robot operation will also be developed and improved.
4. Research on mold materials and surface treatment technology
Due to improper material selection and use, molds fail prematurely, accounting for more than 45% of failed molds. In the entire mold price structure, the proportion of materials is not large, generally 20%~30%. Therefore, it is very necessary to select high-quality steel and apply surface treatment technology to improve the life of the mold. For mold steel, it is necessary to adopt the electro-slag remelting process, which strives to improve the purity, isotropy, density, and uniformity of steel, and develop mold steel with higher performance or special properties, such as powder high-speed steel manufactured by powder metallurgy process.
Powder high-speed steel solves the problem of coarse and segregated primary carbides produced during the original high-speed steel smelting process, thereby affecting the material. Its carbides are fine, the structure is uniform, and there is no material directionality. Therefore, it has the characteristics of high toughness, good grinding processability, high wear resistance, and long-term dimensional stability. Especially for complex-shaped punching parts and high-speed stamping molds, its superiority is more prominent, and it is a very promising steel. Diversification of mold steel varieties and specifications, refinement of products, and productization, as well as shortening delivery time as much as possible are also important development trends.
Heat treatment and surface treatment are the key links to fully exert the performance of mold steel. The main trends of mold heat treatment are: from single-element infiltration to multi-element co-infiltration and composite infiltration (such as TD method); from general diffusion to CVD, PVD, PCVD, ion infiltration, ion implantation, and other directions: the plating that can be used are TiC, TiN, TiCN, TAIN, CrN, Cr7C3, W2C, etc. At the same time, the heat treatment means are developed from atmospheric heat treatment to vacuum heat treatment. In addition, laser strengthening, glow ion nitriding technology, and electroplating (brush plating) anti-corrosion strengthening technologies are also increasingly valued.
5. Mold grinding and polishing will develop towards automation and intelligence
The finishing of the mold surface is one of the problems that has not been well solved in mold processing. The quality of the mold surface has a great impact on the mold service life, the appearance quality of the product, etc. China is still mainly based on manual grinding and polishing, which is not only inefficient (accounting for about 1/3 of the entire mold manufacturing cycle), but also has high labor intensity and unstable quality, which restricts the development of China’s mold processing to a higher level. Therefore, the research on automation and intelligence of polishing is the development trend of mold polishing.
Japan has developed a CNC grinding machine that can realize the automation and intelligence of three-dimensional curved surface mold grinding and polishing. In addition, due to the complex shape of the mold cavity, any grinding and polishing method has certain limitations. Special grinding and polishing, such as extrusion grinding, electrochemical polishing, ultrasonic polishing, and composite polishing processes and equipment should be developed to improve the quality of the mold surface.
6. The application of mold standard parts will become more and more extensive
The use of mold standard parts can not only shorten the mold manufacturing cycle but also improve the mold quality and reduce the mold manufacturing cost. Therefore, the application of mold standard parts will become more and more extensive. To this end, first of all, a unified national standard should be formulated and strictly produced according to the standard; secondly, large-scale production should be gradually formed: to improve the quality of standard parts and reduce costs; thirdly, the specifications and varieties of standard parts should be further increased, and the joint sales network should be developed and improved to ensure rapid supply.
7. The proportion of die-casting dies, extrusion dies and powder forging dies will increase
With the development of lightweight products such as automobiles, vehicles, and motors, the proportion of die-casting dies will continue to increase, and higher and higher requirements will be placed on the life and complexity of die-casting dies. At the same time, the proportion of extrusion dies and powder forging dies will also increase to varying degrees, and the precision requirements will also become higher and higher.
8. New technologies, new concepts, and new models in the mold industry
In the forming (molding) process, there are mainly multifunctional composite stamping dies, superplastic forming (molding), plastic precision forming (molding) technology, plastic mold gas-assisted injection technology and hot runner technology, high-pressure injection molding (molding) technology, etc. On the other hand, with the continuous development of advanced manufacturing technology and the improvement of the overall level of the mold industry, some new design, production, and management concepts and models have emerged in the mold industry. Specifically, they are flexible manufacturing technology that adapts to the production characteristics of single-piece molds; team spirit and lean production that create optimal management and efficiency; new production philosophies such as parallel engineering, virtual manufacturing, global agile manufacturing, and network manufacturing that improve rapid response capabilities; widely adopt the division of labor and cooperative production mode of standard parts and general parts; green design and manufacturing that adapts to sustainable development and environmental protection requirements.
Conclusion
At present, the development pace of China’s mold industry is accelerating, but in terms of the overall mold design and manufacturing level and standardization, there is still a considerable gap compared with developed countries such as Germany, the United States, and Japan. Under the new situation of economic globalization, with the reintegration of capital, technology, and labor markets, China’s equipment manufacturing industry will become the base of the world’s equipment manufacturing industry after joining the WTO.
In modern manufacturing, engineering equipment in any industry is increasingly using products provided by the mold industry. To meet users’ urgent requirements for high precision, short delivery time, and low cost in mold manufacturing, the mold industry should widely apply modern advanced manufacturing technology to accelerate the technological progress of the mold industry, meet the urgent needs of all walks of life for molds, the basic process equipment, and achieve leapfrog development of China’s mold industry.