Rotary moulding process is adapted to ceramics

A highly efficient casting process from the plastics industry has been successfully applied to ceramics for the first time.

A highly efficient casting process from the plastics industry has been successfully applied to ceramics for the first time, offering UK industry the prospect of gaining a new edge in highly competitive markets for tableware, sanitaryware and other ceramic products.

The UK ceramics industry sells almost GBP 2 billion of products a year, ranging from tableware and giftware to advanced ceramics used in high tech applications in the engineering and chemical industries.

Approximately 40,000 people are directly employed by the industry, which has faced intense competition from low-cost producers in the Far East and other developing parts of the world since the late 1990s.

Large amounts of waste are an inevitable by-product of the continued reliance on slip casting using traditional plaster moulds, many of which go to landfill after as few as 40 casts.

The STI project had an ambitious goal - to adapt a processing route established in the polymer industry, to introduce both production flexibility and reduced waste to hollow-item production in the ceramics sector.

Overall savings in production costs as high as 30-40% are estimated by tableware producers taking part in the project.

"Many ceramic production methods have essentially changed little since the days of the Egyptians, 5000 years ago", explains Project Manager Dr Ihsan Al-Dawery of Ceram, the internationally renowned centre for materials and technology.

"The future lies in new, sustainable technology".

"Our research will assist the UK ceramics industry to remain competitive and increase its market share through a shaping process that allows fast introduction of new products and fast changeover of shapes".

"It could be a matter of survival for some pottery producers".

CERAM worked with academic teams from Loughborough University and Queens University Belfast, and a range of industrial partners, including household names such as Spode and Aynsley China in the major project supported by the Sustainable Technologies Initiative (STI).

The STI programme, funded by the DTI, Defra and three research councils, aims to improve the sustainability of UK business by supporting research to achieve economic growth and employment while safeguarding the environment and conserving natural resources.

In this project, researchers sought to adapt the process of rotary moulding (also known as rotomoulding) that is widely used in the plastic industry, where it is used to produce all kinds of hollow plastic products.

The STI researchers had to make the process work with clay-based suspensions used in slip casting ceramic products ranging from cream jugs to toilet cisterns.

"It is the first time that rotomoulding has been applied in the ceramics industry and we have lodged a patent to protect the technology", says Dr Al-Dawery.

"There are considerable advantages".

"Our results show the process has potential to speed up production rates three or four times, reduce labour requirements by 30-40% and make production of tableware and sanitaryware much more flexible".

"The process is also much more environmentally friendly, as whatever goes inside the mould as a suspension becomes the final solid product and there is no waste", he adds.

"There are also benefits in terms of mould materials".

"Currently the UK produces 3000 tonnes of plaster-of-paris waste a year, and the producers have to bear the cost of storing, shipping and getting rid of it all".

"Rotomoulding can employ longer life metal or polymer moulds".

Work on optimising composition of the suspensions was carried out at Loughborough University and continued with a formulation developed by one of the industrial partners, Imerys.

A low-cost coagulant used in the food industry was found to work well, avoiding any problems with unburnt carbon.

Queen's University Belfast led investigations into production of hollow and solid items ranging from teapots and sanitaryware to figurines.

Further trials with a range of cast shapes were carried out on pilot scale moulding equipment constructed by Sorcerer Machinery, one of the consortium partners.

The results showed that medium sized cream jugs with integral handles could be produced using porous moulds in just seven minutes, four times faster than conventional casting.

The jugs were then successfully glazed and fired at pottery factories.

Few problems were encountered - these were low strength of the cast piece and slight pinholing of the glaze.

Initial experimental work by using vacuum mixing has shown a potential to eliminate the formation of pinholes.

Work is continuing to improve the strength.

Commercialisation of the process is anticipated in the near future and there is widespread interest in its potential.

"It's a revolutionary development that should enable the UK industry to compete against intense competition from low cost producers and regain their number one position", says Dr Al-Dawery.

"The STI project played a vital part in achieving such a strong collaborative effort between the industrial and academic partners".

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