Metal powder micro-injection molding technology

Metal powder micro-injection molding technology

Metal powder injection molding (MPIM) is a new forming technology for parts and components, which combines traditional powder metallurgy technology with modern plastic injection molding technology. The biggest feature of this technology is that it can directly manufacture parts with final shape, minimize the amount of machining and save raw materials, and solve the problem of difficult forming of products with complex shape that has troubled the powder metallurgy field for many years; Moreover, the material adaptability of this technology is wide. All metals, alloys, ceramics, etc. that can be made into powder can be made into parts by this technology. In addition, this technology can also realize fully automatic continuous production, with high production efficiency, excellent material performance and high product dimensional accuracy, so it has been widely valued.

The basic process of this technology is as follows: firstly, the solid powder is mixed with a certain polymer and additive component uniformly, and after granulation, the granular material is injected into the mold cavity by the injection molding machine in the heating state for condensation, and then the binder in the forming blank is removed by chemical or thermal decomposition, and finally the final product is obtained by sintering and densification.

In recent years, the development of microsystem technology in various fields has been very rapid. At the same time, higher requirements have been put forward for the manufacture of three-dimensional micro complex components used in micro engineering. It is hoped that the micro components can achieve large-scale production while meeting the performance requirements. The main components in the micro system include micro molds, micro mechanical structures for sensors and accelerators, biosensors, micro fluid components, micro reactors, etc. These components are complex in shape and small in volume. Using existing micro-machining technologies such as micro-cutting, laser cutting, silicon etching, etc., the production efficiency is low, and it is impossible to carry out large-scale production. In recent years, the powder micro-injection molding technology developed on the basis of powder injection molding provides the most potential preparation technology for realizing large-scale production of micro components.

Powder micro-injection molding technology is a kind of molding technology developed on the basis of traditional powder injection molding technology for parts with size less than 1 micron. It is mainly used to continuously manufacture parts with microstructure surface and microstructure. Its basic process steps are basically the same as traditional powder injection molding. The surface quality and porosity of the prepared parts can be controlled by selecting the original powder and appropriate sintering conditions. Different from traditional powder injection molding, the average particle size of powder selected for powder microinjection molding is generally less than 1~2 microns in order to facilitate the manufacturing of micro structures; Secondly, due to the increase of the specific surface area of the powder, the adhesive with low viscosity but sufficient strength is required to facilitate the micro-injection molding and avoid the damage of the green blank during demoulding. In addition, in order to prevent the formation of deformation, cracks and bubbles, the micro-injection molding technology is more stringent on the process conditions of degreasing and sintering.

At present, Germany, Japan, Singapore, the United States and the United Kingdom are the major countries in the world that carry out this technology research. Among them, Germany took the lead and achieved outstanding results. China's Beijing University of Science and Technology, Central South University and Dalian University of Technology have also carried out a series of research work in this field. For example, Beijing University of Science and Technology has developed a mold for powder micro-injection molding with independent intellectual property rights and suitable for traditional injection molding machines; With carbonyl iron powder and iron-nickel alloy powder as raw materials, the powder micro-injection molding of micro-gear with a diameter of less than 1mm was successfully realized on the traditional injection molding machine.