China is an ancient ceramic country with a long history of ceramic culture. Ceramic craft is a variety of products made from natural clay and various natural minerals as the main raw material through crushing and mixing, molding, and calcination of the material.
In the past, people used to call items made of clay that were fired at high temperatures in special kilns as ceramics, and ceramics is a general term for pottery and porcelain.
The traditional concept of ceramics refers to all artificial industrial products made from inorganic non-metallic minerals such as clay. It includes various products made from clay or mixtures containing clay by mixing, forming, and calcining.
The production process of ceramic products refers to the whole process from the input of raw materials until the ceramic products are produced. Generally speaking, the ceramic production process includes three basic stages, such as billet manufacturing, billet forming, and porcelain firing.
At the same time, the composition of the ceramic production process can be divided into production technology preparation process, basic production process, auxiliary production process, and production service process according to the different roles of the production stages.
Ceramic Forming Process
Forming is one of the ceramic manufacturing processes. The ingredients are made into raw billets of a specified size and shape with certain mechanical strength. There are slurry molding methods, plastic molding, dry pressing, semi-dry pressing, isostatic pressing methods, etc.
1. Injection molding method
Slurry injection molding: The slurry is made into a liquid slurry with water, etc. The slurry is injected into the porous plaster model, and the water penetrates into the body of the plaster model through the contact surface, and a hard layer is formed on the surface.
Classification: There are two methods of hollow grouting and solid grouting, and there are methods of pressure grouting, centrifugal grouting, and vacuum grouting to improve the grouting speed and quality.
Process flow: ingredients and water → slurry → injection molding → drying → firing
Process characteristics
Advantages.
The uniform structure of billet, strong adaptability, small investment, suitable for objects with complex shape, irregular, thin, large volume and less strict size requirements, such as vases, soup bowls, teapots, etc.
Disadvantages.
Large shrinkage, long production time, large floor space, large model consumption
Applications.
Applicable to a variety of ceramic products, all complex shapes, irregular, thin, large volume, and size requirements of the object is available injection molding method. General daily-use ceramics in vases, soup bowls, oval plates, teapots, handles, etc.
2. Flow molding
Flow molding: the slurry evenly flow or coated to the support plate, or evenly brushed with a blade to the support surface, forming a slurry film, dried to form a certain thickness of uniform billet film of a slurry molding method
Process characteristics
Advantages.
Less complex equipment, stable process, continuous production, high efficiency, a high degree of automation, uniform film properties and easy to control, suitable for manufacturing a variety of ultra-thin ceramic parts, alumina ceramic substrates, etc.
Disadvantages: small density of billet, high shrinkage
3. Hot die-casting molding method
Hot die-casting molding: Under the action of pressure, the melted wax paste is injected into the metal mold, and then cooled and solidified to get the desired shape.
Process flow.
Dosing → preheating → de-gassing → hot die-casting machine forming → stirring → paraffin → washing into wax cake storage → surface-active substance
Process characteristics
Advantages
1、It is suitable for the molding of new ceramics with mineral raw materials, oxides, nitrides, etc., especially for small and medium-sized products with complex external shapes and high precision.
2, its molding equipment is not complicated, mold wear and tear is small, easy to operate, high production efficiency.
Disadvantages.
The process is more complicated, energy consumption, long working period, for thin-walled large and long products are not applicable.
Applications.
Mainly used for the production of the small and medium-size and complex structures of structural ceramics, wear-resistant ceramics, electronic ceramics, insulation ceramics, textile ceramics, heat-resistant ceramics, sealing ceramics, corrosion-resistant ceramics, heat-resistant shock ceramic products.
4. Plastic forming method
Plastic forming: Various kinds of external forces are applied to the malleable blank, forcing the blank to be plasticized and deformed under the action of external forces to make a raw blank.
(1)Spin molding: Using rotating plaster mold and sample knife for molding, divided into external rotation and internal rotation
Process characteristics
Advantages: simple equipment, strong adaptability, suitable for molding cups, plates, dishes, and other products, as well as large deep-hole products
Disadvantages: not high quality, labor-intensive, requires certain operation skills, low efficiency, etc.
(2) Roll forming: developed by spinning, divided into internal and external rolling
Process characteristics: uniform body structure, dense, strong, smooth surface, high yield, suitable for automated production.
(3) Extrusion molding: extruded by the extrusion machine to extrude the clay into a variety of tubular, rod-shaped, and section and hole in the same product
(4) Injection molding: the ridge material and organic additives are mixed and then the clay is injected into the metal mold cavity by an injection molding machine.
Process characteristics
Advantages: simple process, low cost, uniform density of pressed billets, high dimensional accuracy, short injection cycle, automatic production, suitable for large products of complex shapes.
Disadvantages: long degreasing time (72~96h), expensive metal molds, difficult design
(5) Plastic compression molding: clay material is placed in the model, and the clay material is extruded by adjusting the pressure in the mold at room temperature.
Process characteristics: dense body, a high degree of automaticity, suitable for non-rotationally symmetrical products; requires high strength model, such as porous resin mold, porous metal mold, high cost.
(6) Rolling film forming: Mixing the powder with an organic binder, rolling it into a film by rough and fine rolling
Process characteristics
Advantages: simple process, high production efficiency, smooth, uniform, and dense film surface, simple production equipment, suitable for mass production of 1mm or fewer sheet products.
Disadvantages: large drying shrinkage and firing shrinkage
5. Compression molding method
(1)Dry pressing method
Dry press molding method: The powder with good fluidity and suitable grain mix is loaded into the mold and made into a certain shape by applying external pressure through the plunger of the press.
Process characteristics
Advantages.
1、The process is simple, easy to operate, suitable for mass production, and short cycle time, high work efficiency, easy to achieve mechanized automatic production.
2, because the blank contains less water or other adhesives, dry pressing of the body of high density, size is more accurate, less firing shrinkage, the high mechanical strength of the porcelain body, electrical properties or.
Disadvantages.
1, dry press molding must have a certain power of pressurized equipment, the mold production process requires high.
2, not applicable to the molding of ceramic products with complex shapes.
(2) Semi-dry press molding method
Semi-dry press molding: add less water (7-9%) to the ingredients, mix well and press or pound the molding under high pressure. The size of the product is accurate and the mechanical strength is high.
Process characteristics: accurate shape, high efficiency, complex equipment, and technical conditions.
Applications: miscellaneous parts, arc extinguishers, electrical base plates, and other low-voltage electric porcelain products, etc.
(3) Isostatic molding method
Isostatic molding: the specimen to be pressed in a high-pressure container, the use of liquid media incompressible nature and the nature of the uniform transfer of pressure from all directions to the specimen for uniform pressure, when the liquid medium through the pressure pump into the pressure vessel, according to the principles of fluid mechanics, the size of the pressure constant and uniformly transferred to all directions, through the above method to make the barren powder molding dense blank method is called isostatic method.
Process characteristics: accurate shape, high efficiency, complex equipment, and technical conditions.
Application: porcelain rod and sleeve, spark plug, high alumina electric porcelain, etc.
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