Sanitary ware manufacturing/production process consists of 10 steps from Body preparation to Packing.
In Sanitary ware Manufacturing/Production process body preparation is the first step. In this process, Slip produced by mixing Ball clay, Silica, China clay and feldspar. This composition is called Tri-axial body. Consist of Body former, Filler and flux. Body former is plastic material which is required to give strength at the green stage of the sanitary ware. The filler is non-plastic material which is going to give strength after the firing. Flux is a non-plastic material which added to the body to reduce the fusion temperature point of the body during firing. All raw materials are mixed at the proper position and brought to required physical parameters.
Usually following rheological parameters are checked afterslip preparations – Fluidity, Thixotropic of the slip at 1 minute and 5 minutes, Liter weight.
These parameters will vary depending upon the composition, climate, casting (Bench casting, high-pressure casting, Low pressure casting for sanitaryware and other) and required casting rate.
Supply slip will be a mixture of virgin slip, runoff slip & scrap slip. This composition also will vary according to the availability of the scrap slip available and required casting rate.
Once slip prepared according to the required parameter, it will be sent to slip storage silos. Whenever slip is required, then it will be supplied to the casting department for casting.
In this process, the glaze prepared for spraying department. Body preparation and glaze preparation are a parallel process. Different colours of glaze will be made according to the requirement. The raw material used for glaze preparations is zircon, feldspar, quartz, calcite, china clay and zinc oxide. Raw materials ground in a ball mill and particle size tested before unloaded from ball mill. Alumina ball used in ball mils because of its strength. The glaze will be passed through sieves to remove coarse particles and magnets to remove iron particles. Sample spraying will be done and fired to check the final colour of the glaze. The glaze should be approved by a lab before used in manufacturing/production. Before supply to the spraying, the glaze will be mixed with a binder to give the required properties. Density, drying time, fluidity and viscosity are maintained to get the proper spray.
In this process required shape and size mould will be produced for casting. Case moulds are received form case making section to Moulding section. Case moulds used cast plaster moulds. Mould is prepared using mixing water with Plaster of Paris in a proper ratio. Plaster of Paris chemical formula is CaSO4.1/2 H2O. Usually, the ratio between plaster and water will be around 4:3. This ratio may vary little depends on the purity of the plaster, required strength for the mould, etc. For a single ware up to four moulds for complex models, it will even more. Once the mould prepared, it will be dried in drier to remove the excess water from the mould. This stage is crucial to increase the life of the mould. The plaster used for mould making is known as beta plaster for their absorbent properties. Plaster mould will be used in normal castings. Resin mould is used for high-pressure casting.
There are different types of casting available for sanitary ware. They are normal bench casting, battery casting, beam casting, low-pressure casting and high-pressure casting for sanitaryware. Every casting has its advantage and disadvantages. The process of casting in same in all types of casting, slip is poured into the mould and allowed to form the casting layer on the mould. Then the excess slip is drained through a drain hole. Now casted ware is allowed to dried and then released from the mould. In this stage, the ware known as greenware. This greenware is allowed to dry in atmospheric temperature for one to three days before sent to drier. Before drying that greenware should be finish for smooth joint edges, repair small cracks, small pinholes, bad finishing, etc. Once this ware is ready, it will send to drier for drying. The moisture content of the greenware before drier will be varying from 22% to 12%.
Green piece form casting will be sent to Control and spraying through Drier. In Drier, Green MOR of the ware improved by removing the mechanically combined water from ware. The moisture content of greenware after drier will be varying from 1.5% to 0.5%. The drying process will take from 6.5 hours to 12 hrs. Drier may be batch drier or tunnel drier. The batch drier will be loaded at once and unloaded at once. Tunnel drier will be feeded continuously with ware and continuously discharged at other ends. Gradual heat will be done from atmosphere temperature to 110 C to 120 C. During this process, and ware will lose its weight and shrink in size.
Control & Spraying
In this section, ware will be inspected for a defect. Defected wares will be repaired or rejected depends upon the defects. Usually, the control and spraying department will be handled by the same team. Kerosene is used to find the defects in the wares. Properly checked ware will be sent to spraying are for spraying.
Glaze received from glaze house will be used for spraying. Different colours sprayed in wares as per the production schedule. Manual methods or robotic methods will do the spraying. In spraying 0.8m.m to 1.6 m.m thickness of the glaze is applied on the wares as per the requirement. Once spraying completed, it is allowed some time to dry for a few minutes. Then logo is printed on ware using screen printing method or decal methods. Nowadays after firing also log printing is done by using powered printing machine.
Sprayed ware loaded in kiln car. Dust and other impurities are removed from ware by air blower or vacuum. Usually, The Kiln maximum temperature will be 1250 C. Different types of the kiln can be used for firing (shuttle kiln, tunnel kiln), usually tunnel kiln is used. Shuttle kiln used for refiring. Sanitary ware kiln has three zones, preheating, firing and cooling zones. In preheating zone mechanically and chemically combined water has been removed from the ware. At firing zone, all the raw material are fused together, and glaze is fused evenly. In the cooling zone, sudden cooling is done to create a glossy surface. Once product fired, it will be moved to the sorting area.
In this stage of the process, all wares from the kiln are inspected and sorted according to the Defects. If ware is defects free, then it will be sent to the packing section for packing. If ware has minor defects like pin holes, then it will be repaired by cold fill. It has a light glaze or wavy or blib then it will be sent to refire section. Find All sanitaryware defects. If there is a crack, it will be rejected. This quality check is very important to maintain standards. And also random sampling will be made for a flush test, smoke test, leak test and load test.
All repair wares will be sent to the rework section for minor repairs. All ware is required according to the defect and sent to tunnel kiln. Once repaired and fired again, it will be inspected and again separated as per the grade. If quality standards are met, then it will be sent to packing. If needs repairing again, it will repair in refire section. Major and un-repairable wares will be sent to the rejected area. These are normally warpage or cracked pieces.
It is the final stage of the sanitary ware manufacturing/production process. All Sanitary wares that are passed quality standards are packed and dispatched to the warehouse.
Other than these sections – Lab, New product development and Mould & case are making section also involved in Sanitaryware manufacturing/production process. This process is only an outline of the sanitary ware manufacturing/ production process. All process are discussed in detail in other section.