Using the same mould does not guarantee identical ceramic sanitary ware.
Forming results are jointly controlled by slip condition, casting parameters, and mould temperature and moisture.
Changes in slip density or thixotropy alter filling resistance and dewatering.
Variations in pressure, holding time, drainage or demoulding change wall thickness and green strength.
Differences in mould moisture and temperature change water absorption.
The result can be inconsistent weight, thickness, release time, deformation and cracking, even when the mould geometry is unchanged.
Slip casting is essentially a filtration process. Water moves from the slip through the forming body layer and into the porous mould. Digitalfire explains that specific gravity, viscosity, thixotropy and permeability all influence casting behaviour. A slip containing too much water builds wall thickness more slowly and can waterlog the mould sooner. Slip condition controls flow and dewatering. A slip may meet its density target and still behave differently because of temperature, ageing, particle distribution or deflocculant dosage. Excessive deflocculation can cause settling and poor drainage, while insufficient deflocculation can make the slip gel inside the mould and restrict filling. |  |
One viscosity reading taken immediately after mixing is therefore not enough. Density, temperature and thixotropic recovery should be evaluated together.
Casting parameters control wall thickness and internal stress. Filling rate, pressure curve, holding time, drainage sequence, pressure release and demoulding time determine how quickly particles consolidate and how much strength the green body develops.
A small parameter shift can create thin sections, excessive local thickness or uneven stress, particularly around trapways, corners, mounting surfaces and joints.
Industry practice includes a high-pressure casting system that measures the thickness of the product exiting the cycle and uses feedback to optimize casting time when the rheological properties of the injected slip change. This demonstrates why a fixed timer is less reliable than result-based process control.
 | Mould temperature and moisture control absorption capacity. A mould that has not recovered sufficiently after the previous cycle will absorb water more slowly. Uneven drying across the mould can also produce different dewatering rates in different areas, creating wall-thickness variation and uneven release strength. Research on plaster moulds for sanitary ware found that preparation variables including water temperature, water quality and mixing time altered pore-size distribution, microstructure and casting performance. The study reported that changing water temperature from 38°C to 25°C increased thickness formation by about 9% under the tested conditions. Although this relates to mould manufacture, it confirms that mould pore structure and moisture-transfer behaviour materially affect forming results. |
Record slip density, viscosity, temperature and thixotropic recovery for each batch.
Standardize filling speed, pressure curve, holding time, drainage and pressure-release sequence.
Monitor mould temperature, moisture condition, cleaning status and number of cycles.
Verify results through green-body weight, thickness at critical locations and demoulding deformation.
Trace defects by machine, mould identification number, slip batch, shift and operator.
Use statistical trends to define a process window rather than relying on one fixed timer.
Sunlets combines sanitary ware production, mould development and ceramic forming-equipment manufacturing. This allows slip behaviour, mould permeability, pressure settings and demoulding procedures to be validated as one integrated process, reducing variation during the mass production of complex OEM and ODM products.
The same mould guarantees only the same geometric reference. It does not automatically guarantee the same forming conditions. Stable sanitary ware production requires the slip state, parameter curve and mould temperature-moisture condition to remain within a controlled operating window. When these three factors are monitored together, wall thickness, green-body strength, demoulding and later drying become more predictable. |  |
Why can green-body weight differ between morning and evening shifts?
Slip temperature, thixotropic recovery, storage time or mould moisture may have changed during the day.
Should the mould be modified when wall thickness becomes uneven?
Not immediately. First check the filling path, pressure curve, slip rheology, drainage and mould dewatering condition.