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Slip casting of whiteware products (Composition Function (Dispersing agent…
Slip casting of whiteware products
Stages
clay powder + dipersing agent mixing in water
Pouring of slurry of ceramic body composition into a porous mold
Water drawn out by capillary action
Decomposition of clay particles on the inner surface of mould
Formation of cast
Excess slip removed
Partial drying
Plugging and separating
1 more item...
Composition Function
Dispersing agent - Stabilize the powder against colloidal forces
Solvent - Control slip viscosity and facilitate casting
Binder - Provide green strength to the cast shape
Plasticizer - Modify properties of binder
Advantages
Wide variety of comples shape product
Big and bulky products
Low cost
Disadvantages
Long processing time
Requires large working area
Lower dimension precision
Application
Tubes, boats, figurines,crucibles, turbine blades
Rheology related to flowability which depend on
Slip density
mass / volume
Viscosity
Required viscosity- Spiderweb network structure
Too viscous- Parallel structure
Too low viscosity- Fully open structure
Thixotropy
As an anti-settling that the slip remains fluid when in use but if allowed to stand it turns to a gel
due to agglomeration of
clay in suspension
Type of Casting
Drain Casting
Slip poured into P.O.P mould cavity
Water absorbed
Green cast
Solid Casting
Slip poured into P.O.P mould cavity
Water is absorbed into plaster mould to form a firm layer
Draining of excess slip
Trimming
Finished product
Form of Casting
Bench Casting
1 mould produce 1 product
Battery Casting
Single cast in a row
Pressure Casting
Involved slight external pressure which increase the casting rate
Process variable
Particle size
Larger particles : may sediment during the casting process and the resulting green ceramics sinter less efficiently
Small Particles : Pore spaces between small particles are tortuous and constricting, leading to low dewatering rates.
slip formulation
Influence casting rate, drying shrinkage, green strength, and sinterability
slip viscosity
Easily poured into the mold and fills the detailed sections of the part
Binders (<1 vol%)
Necessary to give the green part enough strength so that it can be removed from the mold and handled when completely dry
