Talking about the current status of MIM process technology today
time:2020-04-29Views:2133 Author:Best Seiko
Deficiencies and defects of MIM process technology: Although MIM process technology can be used to manufacture many products of different materials and shapes, due to the difficulty of MIM forming and degreasing, the general MIM process technology is suitable for producing parts with a mass of less than 500g, while for some large Dimensional parts (wall thickness exceeding 20mm) cannot be produced by this process. Large parts such as cemented carbide and titanium alloy are more difficult to injection mold. Increasing the size of MIM process products through optimization of the MIM process is still a development direction of today's MIM process. After more than 20 years of development in metal injection molding technology, more than 500 companies and research institutes worldwide are engaged in metal injection molding technology. The products have been applied to various industries, including aerospace, weapons, firearms, mobile communication products, Auto parts, office machine products, body leisure products, precision mechanical parts, medical products, keys, power tool parts, optical fiber communication products, bearing parts, watch parts, etc. The material system is also very extensive, including stainless steel, low alloy steel, tungsten alloy, titanium alloy, cemented carbide, ceramics, etc. However, until the end of 2003, the global MIM product market was worth 1 billion US dollars, which was much lower than various predictions. It was still far from a processing technology comparable to machining, precision casting, pressing/sintering and other processes. . The main reason is that metal injection molding technology through the addition and removal of a large amount of binder, although it can solve the problem of complex shapes, but the addition and removal of a large amount of binder makes the existing MIM technology limited to the preparation of small size, low Products and material systems with low accuracy and mechanical properties. At present, the existing metal injection molding technology in the international scope can only prepare products with a thickness of less than 10mm (and more than 5mm), which does not require high microstructure and mechanical properties, and the dimensional accuracy is ±0.3% to 0.5%, such as high-speed steel , Carbide, titanium alloy and ceramic tools, cutting tools, etc. Since the powder/binder plasticizer undergoes many physical and chemical state changes during the MIM process, it is easy to introduce different defects at different stages, so MIM technology is currently in the material system and products that are sensitive to defects and require high mechanical properties. Used less. This is mainly due to the following reasons. Due to the large amount of binder added during the MIM process, the sintering after removal of the binder is similar to the loose sintering of traditional powder metallurgy. Fine powder is used as a raw material to meet the densification requirements, resulting in a substantial increase in cost If the larger size products can only use fine powder, they will not be competitive. At the same time, due to the increase in product size, the time required for degreasing increases exponentially, and the probability of defect occurrence increases significantly. In addition, the product size is increased, the injection molding process time is increased, and the requirements for the rheological properties of the binder are higher, so that it can quickly bring the powder to different parts of the mold cavity. These are the factors that restrict the development of MIM technology to a larger size. So MIM technology has been limited to smaller size products. For the dimensional accuracy, due to the addition and removal of the binder during the MIM process, the sintered product undergoes a very large shrinkage rate (linear shrinkage rate of 10% to 20%) after the binder is removed, at this time various factors All will affect the dimensional accuracy, so it is necessary to establish a mathematical model of the influence of process parameters on dimensional accuracy and establish a real-time monitoring system. The direction of MIM process technology research and development in the future: Although the MIM process is attracting more and more attention, its scale is still weak compared with traditional processing technology, and there is still great potential for development. The new MIM industry also requires us to adopt a series of efforts to develop industrial standards, accelerate industrialization, improve the quality of practitioners, research and develop equipment, and win customers. With the continuous improvement of the process, the superiority of metal injection molding technology has gradually emerged and will be accepted by more and more industries and customers, and the market share it brings is also increasing sharply. Due to the great market potential, many venture capital industries have begun to get involved in the MIM process industry. It is foreseeable that MIM will develop into one of the promising parts manufacturing technologies in the 21st century. In recent years, metal injection molding technology has mainly developed in two directions: the expansion of applicable material systems, and the highly reliable production equipment developed to meet the unique binder and degreasing technology. The performance is as follows: l. Multi-directional expansion of the material system. Injection molding technology is an ideal, near-net forming technology that can be economically shaped, close to the required shape, and requires little or no subsequent processing after sintering. This has become increasingly important in the industrial production applications of precision ceramics. In the production of precision ceramics, it is mainly applied to carbides, cermets, inorganic non-metallic ceramics, oxide ceramics, intermetallic compounds, etc. Taking the zirconia ceramic optical fiber pin as an example, the preparation of green body by injection molding technology can greatly shorten the subsequent processing time. Since the blank formed in the mold cavity already has a certain accuracy of through holes, the subsequent grinding process is reduced to one-third to one-fourth of the extrusion molding, thereby increasing the production rate and greatly reducing the production cost. 2. Diversified binders and multi-channel degreasing technologies. Many binder systems based on cellulose acetate, polyethylene glycol polymer, acrylic polymer, and agar have been further developed and applied. Computer-aided control thermal degreasing technology, solvent degreasing technology, catalytic degreasing technology, as well as freeze drying technology, microwave assisted drying technology have been used for binder degreasing research. The successful application of this technology, on the one hand, shortens the degreasing time (from several days to several hours), on the other hand, it also realizes the control of the side reactions of polymer decomposition that easily produce volatile products during the degreasing process, which is more effective Eliminate the formation of defects in the degreasing process. 3. Go first. Control more precise equipment. Research on computer-precision control of injection molding machines and related online quality monitoring and control systems and development of computer-aided degreasing key equipment technology are the current and future focus directions. Forming equipment, such as powder synchronous injection molding machine, uses a simple and coordinated injection machine to produce composite parts. It is foreseeable that with the further research, development and application of metal injection molding, MIM process technology will truly become a kind of attractive technology that can be developed in parallel with machining, precision casting, pressing and sintering processes in the near future. The near-net shape technology of the force will be understood and accepted by more and more parts designers to meet the needs of high-performance and special-shaped key components in the national communication, machinery, medical, aerospace and other industries, which will reduce China’s zero The parts processing and manufacturing industry has been raised to a new level. 2. The focus of work In the past ten years or so, the industrialization process of the new process of metal injection molding (MIM) has been developing rapidly. The MIM process has good development opportunities, but also faces challenges that need to be taken seriously, especially in the control of dimensional accuracy of MIM parts and the reduction of production costs. 1. Control of dimensional accuracy of parts. Generally, the accuracy of metal injection molded parts is ±0.3. It is much worse than the ±0.1 achieved by the traditional powder metallurgy method. There is still room for improvement in accuracy, mainly through fine process control, sometimes secondary processing, such as machining, heat treatment and polishing. Such follow-up treatment makes users more attractive to products, and at the same time brings more benefits to powder metallurgy parts manufacturers. After secondary processing of metal injection molded parts, the problem of large tolerance can be overcome. Compared with other methods, polishing can also make metal injection molded parts more attractive. 2. Reduce production costs. Utilize measures such as optimized production processes, standardized operations, and waste recycling to save costs. three. Personal suggestions 1. Improve, optimize and standardize the production process, develop high-efficiency and low-cost metal powder production technology and improve production efficiency; 2. Establish various raw materials, binder performance, use specifications, instant market prices, manufacturers And other information databases; 2. Promote the TS16949 management system, establish standardized operating procedures documents and guidelines, and standardize employee operations; 3. Conduct relevant skills training for employees, enhance lean production (lean production) awareness, and improve production efficiency; 4. Benefit strategy: Concentrate on improving sales and employee ratios, pay close attention to benefits, and seek development; 5. Strengthen existing and even potential users and product design departments to communicate and promote the practical application of MIM technology. Work together at the component design stage; 6. If conditions permit, computer simulation and simulation technology of injection molding process flow and filling process can be introduced to save production time and thereby improve production efficiency; 7. Introduce chemical production with highly automated and precise control of the production process Equipment; 8. In the initial stage of the company, strategic management should be carried out, that is, to understand the entire market conditions, competitor information, company strategic positioning, strategic development, etc. 9. Strengthen scientific research cooperation with research institutes and universities, such as research Coarse powder enhanced sintering technology to improve powder utilization, reduce raw material cost of MIM process products, and enhance market competitiveness with other forming technologies;