Linear Guide Rail MHZ2-16D Slide Seat Metal Injection Molding

Process Characteristics

Metal powder injection molding technology is a product of the integration of plastic molding technology, polymer chemistry, powder metallurgy technology and metal materials science. It can use molds to inject molded blanks and quickly manufacture high-density, high-precision, three-dimensional complex shape structural parts through sintering. It can quickly and accurately materialize design ideas into products with certain structural and functional characteristics, and can directly mass-produce parts. It is a new revolution in the manufacturing technology industry. This process technology not only has the advantages of fewer conventional powder metallurgy process steps, no cutting or less cutting, and high economic benefits, but also overcomes the shortcomings of traditional powder metallurgy process products, uneven materials, low mechanical properties, difficult to form thin walls, and complex structures. It is particularly suitable for mass production of small, complex and special metal parts.

Process flow Binder → Mixing → Injection molding → Degreasing → Sintering → Post-processing. 

Powdered Metal Powder

The particle size of metal powder used in MIM process is generally 0.5~20μm; theoretically, the finer the particle, the larger the specific surface area, and the easier it is to form and sinter. The traditional powder metallurgy process uses coarser powder larger than 40μm.

Organic Binder

The function of organic binder is to bond metal powder particles, so that the mixture has rheological and lubricating properties when heated in the barrel of the injection molding machine, that is, it is a carrier that drives the powder to flow. Therefore, the choice of binder is the carrier of the entire powder. Therefore, the choice of binder is the key to the entire powder injection molding. Requirements for organic binder:

1. Small amount, using less binder can make the mixture have better rheological properties;

2. Non-reactive, no chemical reaction with metal powder during the process of removing the binder;

3. Easy to remove, no carbon residue in the product.

Mixed Material

The metal powder and organic binder are evenly mixed together to make various raw materials into a mixture for injection molding. The uniformity of the mixture directly affects its fluidity, thus affecting the injection molding process parameters, and even the density and other properties of the final material. The process of injection molding is consistent with the plastic injection molding process in principle, and its equipment conditions are basically the same. During the injection molding process, the mixture is heated in the barrel of the injection machine into a plastic material with rheological properties, and injected into the mold under appropriate injection pressure to form a blank. The injection molded blank should be microscopically uniform so that the product shrinks uniformly during the sintering process.

Extraction

The organic binder contained in the molded blank must be removed before sintering. This process is called extraction. The extraction process must ensure that the binder is gradually discharged from different parts of the blank along the tiny channels between the particles without reducing the strength of the blank. The removal rate of the binder generally follows the diffusion equation. Sintering can shrink the porous degreased blank to densification into a product with certain organization and properties. Although the performance of the product is related to many process factors before sintering, in many cases, the sintering process has a great and even decisive influence on the metallographic structure and properties of the final product.

Post-processing

For parts with more precise size requirements, necessary post-processing is required. This process is the same as the heat treatment process of conventional metal products.

Features of MIM Process

Comparison of MIM process with other processing technologies

The particle size of raw powder used in MIM is 2-15μm, while the particle size of raw powder used in traditional powder metallurgy is mostly 50-100μm. The finished product density of MIM process is high because of the use of fine powder. MIM process has the advantages of traditional powder metallurgy process, and the high degree of freedom in shape is unattainable by traditional powder metallurgy. Traditional powder metallurgy is limited by the strength and filling density of the mold, and the shape is mostly two-dimensional cylindrical.

The traditional precision casting de-drying process is an extremely effective technology for making complex-shaped products. In recent years, the use of ceramic cores can complete the finished products of slits and deep holes, but due to the strength of the ceramic core and the limitation of the fluidity of the casting liquid, the process still has some technical difficulties. Generally speaking, this process is more suitable for manufacturing large and medium-sized parts, while the MIM process is more suitable for small and complex-shaped parts. Comparison Items Manufacturing Process MIM Process Traditional Powder Metallurgy Process Powder Particle Size (μm) 2-15 50-100 Relative Density (%) 95-98 80-85 Product Weight (g) Less than or equal to 400 grams 10-hundreds Product Shape Three-dimensional Complex Shape Two-dimensional Simple Shape Mechanical Properties Pros and Cons.

Comparison of MIM Process and Traditional Powder Metallurgy Die casting is used for materials with low melting points and good casting fluidity, such as aluminum and zinc alloys. Due to material limitations, the strength, wear resistance, and corrosion resistance of products produced by this process are limited. MIM process can process more raw materials.

Although the precision and complexity of precision casting products have improved in recent years, it is still not as good as the dewaxing process and MIM process. Powder forging is an important development and has been applied to the mass production of connecting rods. However, in general, the cost of heat treatment and the life of the mold in forging engineering are still problematic and need to be further resolved.

Traditional machining methods have recently improved their machining capabilities through automation, and have made great progress in terms of effect and precision, but the basic procedures are still inseparable from the way of completing the shape of parts through gradual machining (turning, planing, milling, grinding, drilling, polishing, etc.). The machining accuracy of mechanical machining methods is far superior to other machining methods, but because the effective utilization rate of materials is low and the completion of its shape is limited by equipment and tools, some parts cannot be completed by mechanical machining. On the contrary, MIM can effectively utilize materials without restrictions. For the manufacture of small, high-difficulty precision parts, the MIM process is relatively low in cost and high in efficiency compared to mechanical machining, and has strong competitiveness.

MIM technology does not compete with traditional machining methods, but makes up for the technical deficiencies or defects of traditional machining methods that cannot be made. MIM technology can play its strengths in the field of parts made by traditional machining methods. The technical advantages of MIM technology in parts manufacturing can form structural parts with highly complex structures.

Injection molding technology uses an injection molding machine to inject product blanks to ensure that the material fully fills the mold cavity, which also ensures the realization of highly complex structures of parts. In the past, in traditional processing technology, individual components were first made and then combined into components. When using MIM technology, it can be considered to be integrated into a complete single part, which greatly reduces the steps and simplifies the processing procedures. Compared with other metal processing methods, MIM has high product dimensional accuracy, no secondary processing or only a small amount of finishing.

The injection molding process can directly form thin-walled and complex structural parts. The shape of the product is close to the requirements of the final product, and the part size tolerance is generally maintained at around ±0.1-±0.3. It is particularly important to reduce the processing cost of cemented carbide that is difficult to machine and reduce the processing loss of precious metals. The product has uniform microstructure, high density and good performance.

During the pressing process, due to the friction between the mold wall and the powder and between the powder, the pressing pressure distribution is very uneven, which leads to uneven microstructure of the pressed blank, which will cause uneven shrinkage of the pressed powder metallurgy parts during sintering. Therefore, the sintering temperature has to be reduced to reduce this effect, resulting in large porosity, poor material density and low density of the product, which seriously affects the mechanical properties of the product. On the contrary, the injection molding process is a fluid molding process. The presence of adhesives ensures the uniform arrangement of powders, thereby eliminating the unevenness of the microstructure of the blank, and then the density of the sintered product can reach the theoretical density of its material. Under normal circumstances, the density of the pressed product can only reach 85% of the theoretical density. The high density of the product can increase the strength, strengthen the toughness, improve the ductility, electrical conductivity and thermal conductivity, and improve the magnetic properties. High efficiency, easy to achieve large-scale and large-scale production.

The metal mold used in MIM technology has a lifespan comparable to that of engineering plastic injection molding molds. Due to the use of metal molds, MIM is suitable for mass production of parts. Since the blank of the product is molded by an injection machine, the production efficiency is greatly improved and the production cost is reduced. In addition, the consistency and repeatability of the injection molded product are good, which provides a guarantee for large-scale and large-scale industrial production. It has a wide range of applicable materials and a broad application field (iron-based, low alloy, high-speed steel, stainless steel, clad alloy, cemented carbide).

The materials that can be used for injection molding are very wide. In principle, any powder material that can be cast at high temperature can be made into parts by MIM process, including difficult-to-process materials and high-melting-point materials in traditional manufacturing processes. In addition, MIM can also conduct material formula research according to user requirements, manufacture any combination of alloy materials, and mold composite materials into parts. The application fields of injection molded products have spread throughout various fields of the national economy and have broad market prospects.

Qinhuangdao Zhongwei Precision Machinery Co., Ltd. was founded in 1997 and is a manufacturer and technical solution provider focusing on metal powder injection molding (MIM) products, investment casting products, and precision forging products. With a strong R&D team and technical strength, we provide customers with fast and effective solutions and stable product supply.

Since its establishment, the company has always adhered to the principle of customer-oriented, quality-first, independent innovation and continuous improvement. Technology-first development policy.

The company's main business is the R&D, design, production and sales of metal product structural parts. The products can be widely used in key application fields such as consumer electronics, medical devices, and automobiles. It has advantages and rich experience in product R&D, mold development, process design, product manufacturing, quality control, etc.

The company has a stable core team, a strong technical team, and has introduced advanced equipment to form the core competitiveness of MIM products in the industry and become a strategic partner of MIM products for international customers.