A globally popular material - ceramic is quite brittle and hard. But is it possible to machine it and how does it obtain the complex shapes that are so common in everyday life?
Ceramic production refers to the process of manufacturing ceramic materials and products. Ceramics are a versatile material made from inorganic, non-metallic compounds and are used in many areas of everyday life. Ceramic production involves a large number of production steps (processes) until it becomes a finished product. Figure 1 illustrates the most important processes in ceramic production using the example of the manufacture of implants. It does not acquire product-specific properties immediately and can be processed quite easily using conventional machining processes such as turning, milling and drilling in certain green machining processes. In relation to ceramics, ‘green machining’ refers to the phase of machining ceramic workpieces in a raw or incomplete state after they have been removed from a mould, but before they reach their final state through sintering.
Classification of ceramics
The first step in ceramic processing is to procure the required raw materials. These raw materials can include different types of clay, kaolin, feldspar, quartz and other mineral compounds, depending on the specific properties and requirements of the end product.
Some of the most common types of ceramics are:
Oxide ceramics
Aluminium oxide (Al2O3): It is one of the most commonly used technical ceramics and is characterised by high hardness, wear resistance and thermal stability. It is often used for grinding and cutting tools, resistors and insulators.
Zirconium dioxide (ZrO2): Known for its high toughness and fracture resistance, it is used in dental implants, ball bearings and other applications that require strength and toughness.
Silicon carbide (SiC): Silicon carbide is an extremely hard material with excellent thermal and chemical properties. It is often used in abrasives, grinding wheels, seals and high-temperature applications.
Nitride ceramics
Silicon nitride (Si3N4): It is known for its high strength, toughness and heat resistance. It is used in rolling bearings, high-temperature seals and turbine components.
Aluminium nitride (AlN): An excellent heat conductor used in electronic components and high-performance electronics.
Carbide
Tungsten carbide (WC): It is extremely hard and is often used in hard metals for cutting tools and wear parts.
Titanium carbide (TiC): A hard material used in coatings, cutting tools and high temperature applications.
Porcelain
Porcelain is a special form of ceramic produced by firing a mixture of kaolin and other materials at high temperatures. It is often used for crockery, tiles and decorative items.
Glazes and enamels
These ceramics are normally used as surface coatings on other ceramic materials to seal, decorate and waterproof them.
Ceramic production
During ceramic processing, the raw materials are crushed and ground to achieve the desired grain size and distribution. This step improves the miscibility of the raw materials and facilitates further processing. Ceramics are often pressed in a powder or paste form and then sintered at high temperature to obtain a solid and durable structure. During the green processing of ceramics, the workpieces still have a porous, incomplete structure and are usually far less solid than the final sintered material. Green machining allows rough shaping, usually with the diamond cutting tool, the removal of excess material and initial machining to be carried out before sintering and is therefore a crucial step in the manufacture of ceramic products. The sintering process increases the density and strength of the ceramic and leads to a complete bonding of the particles, giving the final product its final mechanical and physical properties. Extremely hard cutting tools such as diamond grinding discs or diamond suspensions are often used in the hard processing of ceramics. Grinding is a frequently used method in the hard machining of ceramics. It involves removing material from the workpiece surface to achieve the desired shape and surface quality.
After grinding, surface treatment by polishing may be required to achieve the desired surface finish and tribological properties. Cleaning in ceramic manufacturing is an important step to ensure that the manufactured ceramic products are free of impurities, dust, dirt or other residues. Thorough cleaning is crucial, as even the smallest impurities can affect the quality of the ceramic products. Finally, extensive testing and inspection of the finished products must be carried out to ensure that they meet the quality standards and specified tolerances (Figure 2). This may include mechanical tests, chemical analyses, surface inspections, visual inspections and other testing procedures.
The production of ceramic implants requires the highest precision and quality control, as the implants are used in the human body and must ensure that they are biocompatible, mechanically stable and durable. The production of medical implants is subject to strict regulatory requirements and quality standards to ensure patient safety.
Ceramic manufacturing is used in many applications, including the production of tableware, tiles, sanitary ceramics, electronic components, insulators, abrasives, and even in medicine. It is a complex process that can involve both traditional craftsmanship and modern technologies to produce high-quality ceramic products.
Reference:
[1] YouTube channel „Mathys AG Bettlach“