The process starts by checking the alumina and other additives for correct chemical composition and subsequently storing them in different silos connecting to a continuous ball mill. All the tank, silo and ball mill input-output are controlled by SKADA to eliminate the manual errors in the process.

The alumina and additives are sent to a continuous ball mill as per the required formulation and milling operation is performed to get uniformly fine material. The material is then sent to agitator tanks for mixing the binders into the ceramic powder uniformly. After the agitator there is a quality check for the viscosity and particle size characterization. From the agitators this material in the form of a slurry goes to spray dryer.

Spray drying is a method of producing a dry powder from a liquid or slurry by rapidly drying with a hot gas. This rapid drying ensures that the produced powder is uniformly sized and is of free flowing nature to give compaction during molding. After the powder is cooled in a cooling chamber it is sieved in a shifter mesh to separate all the different sizes present in the powder.

Before sending the ceramic powder for molding our quality and R&D team ensures that the powder will give the desired shrinkage after firing by performing a slug characterization.

Subsequently, the pressure is applied by the top ram which is in relative movement to the feeder box and depth of mould. Facilities up to 250 tonnes capacity are available for pressing at our plant. Next process is ejection of the tile which is controlled by cams, sensors or CNC program and in accordance with the position of ram and feeder box. Ejection of tile is achieved by the robotic arm. Tiles up to 100mm thickness and 220mm length can be moulded with the facility. Tiles are fired only after required quality tests are conducted.

The working principle of cold isostatic pressing is that powder is compacted by applying uniform pressure in all directions thus achieving maximum uniformity of density and microstructure without the geometrical limitations of uniaxial pressing. In cold isostatic pressing (CIP) the powder is placed in a flexible mould made of rubber or Urethane or PVC that does not change shape, but preserves the shape from the mould. It uses a liquid media, such as water or an oil or glycol-mixed water, to apply uniform pressure around the circumference of mould. Typically Pressures of 35-690 MPa are used at ambient temperature or slightly elevated temperatures to compact the powder. Cold iso static pressing parameters of pressure and time are pre-determined to give the material full density.

Cold isostatic pressing has the advantage for producing very large or complex shaped parts and also in the cases where the high initial cost of pressing dies cannot be justified. Using CIP, variety of powders can be pressed isostatically on a commercial scale including metals, ceramics, plastics and composites.

CIM technique provides more freedom to engineers to design components without any limitations normally imposed by other ceramic forming techniques. After obtaining the 3-d design & drawing of the part, the prototype is CNC machined using 3-axis or 5-axis milling machine. With the help of the prototype, the tool is manufactured. The moulding process starts with very fine ceramic powders which are then mixed with binders such as paraffin wax, carnauba wax and polyethylene wax to form homogeneous palletised feedstock.

The slurry of binders along with the ceramic powders goes into the mould during the injection stage. The molten feedstock is forced into a mould cavity which takes the shape of the mould (can be single or multi-cavity configurations). Then it goes through two thermal processes. First is de-binding to remove the binder by sintering part in a high temperature kiln (1500-1650 ºC) to form a dense ceramic component. During this process, the component shrinks uniformly by 18-20 % while retaining the complex shape. The process can achieve tighter tolerances without post sintered finishing operations. Then surface roughness testing and other visual inspections are done and the product is sent for dispatch.

To ensure the best bonding between the ceramic surface and Nickel/Silver plating, Moly-Manganese paste is used which has excellent adhesion to the ceramic surface. Ceramics are washed thoroughly before metallization with various stages of demineralized water, acidic and basic solutions to ensure no contamination affect the bonding of Moly-Manganese paste to the ceramic surface. Cleaned ceramics are moved to class IV clean room with particles less than 50 ppm (parts per million) for metallizing, minimizing any chances of defects. Metallized ceramics are fired with appropriate temperature to remove the volatiles from the paste and strengthening the bond between Moly-Manganese and ceramic surface. Ceramics are inspected for the uniformity of the metallization.

After ensuring the proper metallization, ceramics are moved for Nickel/Silver plating process which acts as the medium for brazing of two different ceramics.