Ceramic molding is an important part of the ceramic preparation process. The molding technology largely determines the uniformity of the billet and the ability to prepare complex shaped parts, and directly affects the reliability of the material and the cost of the final ceramic parts.
one:
Dry pressure forming
Dry press molding, also known as the die molding, is one of the most commonly used molding methods. Dry pressure molding is to load the appropriate powder after granulation, good fluidity and particle grading into the metal mold cavity. Apply pressure through the pressure head, and the pressure head shifts in the mold cavity to transfer the pressure, so that the powder particles in the mold chamber deform and are compacted, forming a ceramic billet with a certain strength and shape.
Main factors affecting dry pressure forming:
(1) Powder properties: particle size, particle distribution, fluidity, water content, etc.;
(2) Selection of binder and lubricant;
(3) Mold design;
(4) Suppression force, pressure pressing mode, pressure speed and pressure holding time during the suppression process.
In conclusion, if the billet particle grading is appropriate, the binder is used correctly, the compression method is reasonable, and the dry pressure method can also obtain the relatively ideal billet density.
Advantages of dry pressure molding:
(1) Simple process, convenient operation, short cycle, high efficiency, facilitate the implementation of automatic production.
(2) Large blank body density, accurate size, small shrinkage, high mechanical strength, good electrical performance.
Disadvantages of dry pressure forming:
(1) It is difficult to produce the body of large billet, with large mold wear, complex processing and high cost.
(2) The izing can only be pressed up and down the pressure, pressure distribution is uneven, uneven density, uneven contraction, will produce cracking, stratification and other phenomena. However, with the development of modern forming method, a disadvantage is gradually overcome by isostatic molding.
Application: especially suitable for the preparation of various ceramic products with small section thickness, such as ceramic sealing ring, ceramic valve core, ceramic lining plate, ceramic lining, etc.
two:
tape casting
Flow extension forming is also known as scraper molding. Its basic principle is that the ceramic slurry with suitable viscosity and good dispersion flows from the mouth of the slurry groove to the baseband. Through the relative movement of the substrate and the scraper, it forms the blank film with a smooth upper surface under the action of the surface tension. The thickness of the blank film is mainly regulated by the gap between the scraper and the baseband. The blank film enters the drying room with the baseband, and the solvent evaporation organic binder forms a network structure between the ceramic particles, forming the blank with certain strength and flexibility. The dry blank and the baseband are stripped before the coil. Then the desired shape is cut, punched or punched, and finally through sintering to get the finished product.
The flow forming process can be divided into non-water based flow forming, water based flow forming, gel flow forming, etc.
The process of preparing the ceramic substrate includes the slurry preparation, fluid extension molding, drying, degreasing, sintering and other processes, among which the most critical is the preparation of the slurry and the control of the fluid extension process.
Advantages: flow forming can prepare several micron to 1000 μ m smooth ceramic sheet material, and simple equipment, stable process, can be continuous operation, easy to automation, high production efficiency, consistent product performance, so it is the most important and effective process of single or multilayer sheet material.
Disadvantages: the binder content is high, so the shrinkage rate can reach 20%~21%.
Application: Monolithic capacitor porcelain piece, thick