New Technique Could Break the Mould in Ceramics Production

CERAM is heading an investigation that could help the Ceramics Industry enjoy reduced production costs and more production flexibility thanks to the adaptation of the Rotational Moulding (RM) technique that is already well established in the plastics industry.

A team from CERAM, Loughborough University and Queens University, Belfast is leading a consortium in the project which is funded by the DTI under the "Sustainable Technologies Initiative" scheme.

In the production of plastics using RM, powdered polymer (often polyethylene) is tipped into a mould that is subsequently rotated around two axes whilst being heated. The polymer particles melt, coalesce and evenly coat the inner mould to create a hollow cast piece that can be de-moulded after cooling.

The project is investigating an adaptation of RM for ceramics in which a powder feedstock is replaced with a high solids content slurry. During rotation of the closed mould, a temperature rise induces an increase in viscosity and then solidification.

Phil Jackson, (Head of the Applications Group within CPM) at CERAM explained: "The general term for this solidification is "Direct Consolidation" and requires the use of special chemical additives. Direct Consolidation has been explored by the advanced ceramics community for some time now. However, by using RM with direct consolidation, more complex non-solid cast items can be delivered; this should have appeal right across the various ceramic sectors."

The current STI project focuses on tableware and sanitaryware. For these sectors, the potential advantages of RM and direct consolidation methods over conventional and pressure casting include a reduction in costs associated with plaster mould production and disposal, as well as relatively low capital expenditure, which will attract SMEs that wish to retain manual work, and larger companies that are considering inter-process handling. It should also result in improved production flexibility and cast surface quality, with reduced reliance on plaster and other associated costs.

A pilot unit has recently been built and installed at CERAM to demonstrate the RM casting, of tableware and sanitaryware items. The STI project consortium had patented the technology and now holds joint ownership.