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 is 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. 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 proper position and brought to required physical parameters.
Normally following rheological parameters are checked after slip preparations – Fluidity, Thixotropic of the slip at 1 minute and 5 minute, Liter weight.
These parameters will vary depending upon the composition, climate, Type of casting (Bench casting, high pressure casting, Low pressure casting for sanitaryware and other) and required casting rate.
Supply slip will be mixture of virgin slip, run off 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 casting department for casting.
In this process glaze is prepared for spraying department. Body preparation and glaze preparation are parallel process. Different colors of glaze will be prepared according to the requirement. Raw material of the glaze preparations are zircon, feldspar, quartz, calcite, china clay and zinc oxide. Raw materials are grinded in ball mill and particle size is tested before unloaded from ball mill. Alumina ball is used in ball mils because of its strength. 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 color of the glaze. Glaze should be approved by lab before used in manufacturing/production. Before supply to the spraying, glaze will be mixed with binder to give required properties. Density, drying time, fluidity and viscosity are maintained to get proper spraying .
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 are used cast plaster moulds. Mould is prepared using mixing water with Plaster of Paris in proper ratio. Plaster of Paris chemical formula is CaSO4.1/2 H2O. Normally 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 and etc. For a single ware up to four moulds for complex models it will even more. Once mould is prepared it will dried in drier to remove the excess water from the mould, this stage is crucial to increase the life of mould. Plaster used for mould making is known as beta plaster for their absorbent properties. Plaster mould will be used in normal castings, resin mould are used for high pressure casting.
There are different types of casting available. Some of the types are normal bench casting, battery casting for sanitaryware, beam casting, low pressure casting and high pressure casting for sanitaryware. Every casting has its own advantage and disadvantages. The process of casting in same in all types of casting, slip is poured into the mould and allowed to form casting layer on the mould. Then the excess slip is drained through drain hole. Now casted ware is allowed to dried and then released from mould. In this stage the ware is known as green ware. This green ware is allowed to dry in atmospheric temperature for one to three days before sent to drier. Before sending to drier this green ware is finished to smooth joint edges, repair small cracks, small pin holes, bad finishing and etc. once this ware is ready it will be sent to drier for drying. Moisture content of the green ware 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 is improved by removing the mechanically combined water from ware. Moisture content of green ware after drier will be varying from 1.5% to 0.5%. Drying process will take from 6.5 hour to 12 hrs. Drier may be batch drier or tunnel drier. Batch drier will be loaded at once and unloaded at once. Tunnel drier will be feeded continuously with ware and continuously unloaded at other end. Gradual heat will be done from atmosphere temperature to 110 C to 120 C. During this process ware will loss his weight and shrink in size.
Control & Spraying
In this section ware will be inspected for defect. Defected wares will be repaired or rejected depends upon the defects. Normally control and spraying department will be handled by 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 colors are sprayed in wares as per the production schedule. Spraying will be done by manual methods or robotic methods. 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 done allowed some time to dry for few minutes. Then logo is printed o ware using screen printing method or decal methods. Now a days after firing also log printing is done by using powered printing machine.
Sprayed ware will be loaded in kiln car. Dust and other impurities are removed from ware by air blower or vacuum. Kiln maximum temperature will be 1250 C. Different types of kiln can be used in firing (shuttle kiln, tunnel kiln), normally tunnel kiln is used for firing. Shuttle kiln is used for refire. Sanitary ware kiln have three zones, pre heating, firing and cooling zones. In pre heating zone mechanically and chemically combined water has been removed from the ware. At firing zone all the raw material are fused together and glaze are fused evenly. At cooling zone sudden cooling is done to create glossy surface. Once product fired, it will be moved to 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 send to packing section for packing. If ware has minor defects like pin holes then it will be repaired by cold fill. If has 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 flush test, smoke test, leak test and load test.
All repair wares will be send to rework section for minor repairs. All ware are 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 sent to packing. If needs repairing again it will repaired in refire section. Major and un-repairable wares will be sent to rejected area.These are normally warpage or cracked pieces.
It is the final stage of sanitary ware manufacturing/production process. All Sanitary wares that are passed quality standards are packed and dispatched to ware house.
Other than these sections – Lab, New product development and Mould & case making section also involved in Sanitaryware manufacturing/production process. This process is only an outline of sanitary ware manufacturing/ production process. All process are discussed in detail in other section.