POWDER INJECTION MOLDING
Powder injection moulding (PIM) is a new forming technology for parts, which combines traditional powder metallurgy technology with modern plastic injection moulding technology. The most important feature of this technology is that it can directly produce the parts with the final shape, reduce the amount of machining and save raw materials to the greatest extent, and solve the difficult problem of forming complex shape products which have been puzzling the field of powder metallurgy for many years; moreover, the material adaptability of this technology is wide, and all metals, alloys and ceramics that can be made into powder can be made into parts by this technology. 。 In addition, the technology can also realize automatic continuous production, high production efficiency, excellent material performance, high dimensional accuracy of products, so it has been widely valued.
The basic technology of this technology is: firstly, the solid powder is mixed with certain polymer and additive components evenly, after granulation, the granular material is injected into the mould cavity by an injection moulding machine in the heating state, 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 is very rapid. At the same time, it puts forward higher requirements for the manufacture of three-dimensional micro-complex components used in micro-engineering. It is hoped that micro-devices can achieve large-scale production while meeting the performance requirements. The main components of the micro-system include micro-molds, micro-mechanical structures for sensors and accelerators,
biosensors, micro-fluid elements, micro-reactors and so on. These components are complex in shape and small in size. The existing micro-processing technologies such as micro-cutting, laser cutting and silicon etching have low production efficiency and are unable to carry out large-scale production. Powder micro-injection moulding technology developed on the basis of powder injection moulding in recent years provides the most potential preparation technology for large-scale production of micro-components.
Powder micro-injection moulding (PIM) is a kind of moulding technology developed on the basis of traditional powder injection moulding (PIM) technology. It is mainly used in continuous manufacturing of parts with micro-structure and micro-structure.
Its basic technological steps are basically the same as those of traditional PIM. The surface quality and porosity of the parts can be obtained by choosing the original one. Powder and suitable sintering conditions are controlled. Different from traditional powder injection moulding (PIM), the average particle size of powders selected by PIM is generally less than 1-2 microns in order to facilitate the manufacture of micro-structures. Secondly, due to the increase of specific surface area of powders, a binder with low viscosity but
sufficient strength is needed to facilitate MIM and avoid the damage of green parts during demoulding. In addition, in order to prevent the formation of deformation, cracks and bubbles, the process conditions of degreasing and sintering are more stringent by micro-injection moulding technology.
At present, Germany, Japan, Singapore, the United States and the United Kingdom are the main countries in the international research on this technology. Among them, Germany took the lead and achieved outstanding results. Beijing University of Science and Technology, Central South University and Dalian University of Technology in China have also carried out a series of research work in this field. For example, Beijing University of Science and Technology has developed a powder micro-injection moulding die with independent intellectual property rights, which is suitable for traditional injection moulding machine. With carbonyl iron powder and iron-nickel alloy powder as raw materials, micro-gear with top circle diameter less than 1 mm has been successfully manufactured by powder micro-injection moulding on traditional injection moulding machine.