Ceramic Molding


Ceramic Injection Molding (CIM) is a new process for preparing ceramic parts developed by combining the polymer injection molding method with the ceramic preparation process. Similar to the metal injection molding (MIM) technology developed in the 1970s, they are the main branch of powder injection molding (PIM) technology and are developed on the basis of the relatively mature polymer injection molding technology. For the mass production of ceramic products with high dimensional precision and complex shapes, the use of ceramic powder molding is the most advantageous.

cearmic injection molding ceramic parts

01. Characteristics of CIM ceramic injection molding technology


Ceramic moulding compared with other ceramic methods
Forming method Forming material Crystal shape Diameter Thickness Production efficiency Technical essentials
Injection molding Powder + organic material (10%~25%) complexity 30~0.5 3.0~1 Mass production Additive selection; degrease
Mechanical pressing Powder + organic material (4%~8%) easy 20~1.0 0.8~1.0 Intermittent, automatic mass production Particle adjustment
Cold isostatic pressure Powder + organic material (3%~8%) More complex cylindrical spheroids 150~3 150~1.9 Flow production Particle adjustment, mold production
Slurry casting Powder + various materials + water complexity 150~20 3.0~0.3 Batch production Control particle size and adjust paste
Doctor blade Powder + various materials + organic solvent easy 200~15 0.2~0.003 Automatic mass production Particle size distribution, pulp adjustment, organic matter selection
Extrusion Powder + various materials + water Rod-shaped tube 30~20 2.5~0.01 Continuous mass production Additive selection


Advantages of Ceramic Molding:

The forming process has the characteristics of high mechanization and automation, high production efficiency, short forming cycle, and high strength of billet, and its process can be accurately controlled (program control), easy to achieve mass and large-scale production;

(2) It can be net-formed a variety of small ceramic parts with complex geometric shapes and special requirements so that the sintered ceramic products do not need to be machined or processed less, in order to reduce the expensive ceramic processing costs;

③ The formed ceramic products have extremely high dimensional accuracy and surface finish.

Disadvantages: disposable equipment investment and high processing costs, only suitable for mass production.

ceramic parts

02.Ceramic injection molding process

The manufacturing process of ceramic precision injection molding is shown in Figure 1, which mainly includes the following four links:

① Feeding preparation:

The feed is a mixture of powder and binder. The injection process requires that the injection feed has good fluidity, which requires the selection of the required powder and the appropriate binder system, according to a certain loading ratio, and the appropriate method is mixed into a uniform injection molding feed at a certain temperature, so as to ensure the smooth progress of the post-sequence process, and its products are likely to go from the laboratory to the high-tech market. So feed preparation is very critical in the whole process.

②Ceramic molding and mold design:

Improper control of the injection molding process may cause many defects in the product, such as cracks, pores, welds, delamination, powder and binder separation, etc., and these defects are not found until degreasing and sintering. CIM often uses multi-cavity dies, and the sizes of each cavity are different, and the wear and tear of the cavity during use will lead to different sizes of parts. In addition, the use of injection return material will affect the viscosity and rheology. Therefore, the control and optimization of injection temperature, mold temperature, injection pressure, pressure holding time, and other molding parameters are essential to reduce the fluctuation of green weight, prevent the separation and segregation of each component in the injection material, and improve the product yield and material utilization rate.

The mold design of CIM technology mainly considers the flow control of feed in the mold cavity during injection molding. Because most of the CIM products are small parts with complex shapes and high precision requirements, it is necessary to carefully design and arrange the location of the feed port, the length of the flow channel, and the location of the exhaust hole. Of course, mold design requires a clear understanding of the rheological properties of the feed, the temperature in the mold cavity, and the residual stress distribution, and computer simulation technology will play an important role in the design of powder injection molding molds.

ceramic injection mold

③ Degreasing process:

Degreasing is the process of removing organic matter from the molding body by heating and other physical methods and producing a small amount of sintering. Compared with the process of batching, forming, sintering, and post-processing of ceramic parts, degreasing is the most difficult and important factor in injection molding. Incorrect process methods and parameters in the degreasing process make the product shrink inconsistently, resulting in deformation, cracking, stress, and inclusion. Degreasing is also important for subsequent sintering, and the cracks and deformation generated during degreasing cannot be remedied by sintering. The binder and degreasing are linked together to determine the degreasing method. At present, in addition to the traditional thermal degreasing and solvent degreasing, there are also catalytic degreasing and water-based extraction degreasing developed in recent years.

④ Sintering:

After degreasing, the ceramic blank is densified and sintered at high temperatures to obtain the compact ceramic parts with the required appearance shape, dimensional accuracy, and microstructure. Because the ceramic injection molding blank contains pores left by degreasing, the shrinkage rate of the product is large during sintering, usually up to 13%-15%. It can be seen that the research focus of CIM technology is the control of sintering dimensional accuracy. In addition, sintering equipment is also the key to sintering technology.

03. CIM ceramic injection molding application examples

At present, the injection molding process has been applied to the preparation of various high-performance ceramic products. Such as ceramic medical instruments in the biomedical field, ceramic brackets and ceramic dental posts for orthodontics and restoration; Zirconia ceramic core and ceramic sleeve for optical communication; Alumina-insulated ceramic components used in the semiconductor and electronics industries, such as integrated circuit high-package housing, small vacuum switch ceramic housing small ceramic sliding shaft core; Ceramic knives, ceramic watch chains and ceramic watch cases used in modern life and watchmaking.

Ceramic molding parts application field

Application field Typical product
Aerospace industry Turbine rotor, blade, aircraft spacecraft bearing, accessory rocket nose cone
Automobile industry Spark plug, automotive engine, valve, piston, turbocharger rotor, nozzle
Electronics industry Optical fiber guide, integrated circuit board, resistor, heating element
Medical treatment Artificial bones, artificial joints, artificial gums, dentures, medical knives
Daily necessities Watch case, hair clippers, insulator, spring
Machinery industry Gears, screws, nuts, cutting tools, seals, wire drawing dies, ball grinding parts

ceramic molding

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