Building on current success for precision ceramic components

UK-based producer looks to build on current success for precision ceramic components.

Morgan Advanced Ceramics, a division of Morgan Crucible Company plc, sees a bright future for ceramic injection moulded (CIM) parts. PIM International recently visited the company’s multi-million pound CIM facility in Stourport, UK.

Company history
Morgan Advanced Ceramics located in the central England town of Stourport-on-Severn, Worcestershire, is a division of The Morgan Crucible Company plc. In 2006 the parent company celebrated two important anniversaries – 150 years of continuous trading since the Morgan brothers first started producing crucibles in Battersea, London in 1856, and 60 years being listed on the London Stock Exchange. The company has recently gone through significant restructuring of its nine business units that existed in 2003. Three of these business units have been merged to become the Carbon division, a further two have become the Technical Ceramics division and the Thermal Ceramics and Crucibles businesses report as the Insulating Ceramics division. In 2004, the Automotive & Consumer business was sold, and the sale of the Magnetics division was completed in December 2005. Morgan Crucible’s three divisions reported global annual sales of around £750 million in 2005. Around £150 million of sales was for technical ceramics making Morgan one of the world’s leading companies in this sector with manufacturing facilities located in Europe, North America and Asia.

Included in the Morgan Advance Ceramics (MAC) business are the multi-million pound ceramic injection moulding facilities in Stourport, and metal injection moulded (MIM) part production which is located at Alberox Products, New Bedford, Mass., USA. Alberox Products became part of the Morgan Crucible company in 1989. PIM International’s focus on this occasion was the Stourport CIM facility.

Advanced Ceramic Manufacturing at Stourport
There has been ceramic component production at MAC’s Stourport site for nearly 78 years. The original factory was built by Stemag of Germany in 1929 and was used to manufacture steatite and porcelain products until it was sold to ICI in 1941. The site was acquired by Morgan Crucible in 1964 as part of its venture into technical ceramics.

Approximately 300 people are today employed by MAC in Stourport, and the facility is regarded as the “centre of excellence” for ceramic materials production for the Morgan Technical Ceramics division, providing ceramic powders and ready-to-press spray dried agglomerated materials for all other technical ceramic and advanced ceramic manufacturing sites in Europe, and even the USA and China. Materials include high purity 99.5% Alumina, Zirconia Toughened Alumina (ZTA), Zirconia, silicon carbide and others.

The bulk of production at MAC in Stourport evolves around a wide range of advanced ceramic components produced by dry pressing, isostatic pressing, extrusion, and injection moulding. Typical high volume ceramic products include valve seals, shafts and bearings for hot water pumps in central heating systems, extruded cable insulators, to name just a few. Most of these components have relatively simple shapes and do not have to be produced to very close dimensional tolerances. For more complex ceramic shapes and tighter tolerances/improved surface finish then expensive secondary machining and grinding operations are necessary. However, advances in ceramic powder injection moulding technology has opened up new opportunities to produce medium to large volumes of highly complex, ultra-high precision ceramic components. MAC recently unveiled some success stories being achieved at its new state-of-the-art powder injection moulding facility which was opened in 2004. The CIM facility is said to occupy some 15% of the total land space at the Stourport site and employs up to 40 staff – depending on order throughput.

Investment in Ceramic Injection Moulding
Paul Manison is project manager responsible for MAC’s ceramic injection moulding facility and was our guide during a recent visit. He told PIM International that the new CIM plant was a significant investment for the company and a commitment to developing new markets for its CIM products. “We are after high-tech ceramic parts and we want to be a leader in our field. With our advanced CIM technology we can achieve intricate geometries with features unique to injection moulding such as re-entrant angles, multi-shaped blind holes, external and internal screw threads, surface profiles, perpendicular holes, undercuts and intricate cavities”. The combination of intricate shapes and the superior wear characteristics of ceramics has already seen MAC notch up some notable successes, which are outlined below and more than 30 high volume CIM parts are in production or under development.

Powders and Feedstock
As already mentioned MAC undertakes the manufacture of all its own powder and feedstock requirements in-house at Stourport. Powders are produced with purity of up to 99.5% for alumina and zirconia, with ultrafine and sub micron particle sizes required for the ultra-high precision ceramic parts. MAC compounds the fine ceramic powders with a polymer binder to produce the pelletized feedstock. The ceramic powder to binder ratio was said to be about the same as for metal powder injection moulding.

Paul Manison stated that it is important to have good quality control in the mixing of ceramic powders and polymer binder in order to achieve a homogeneous moulding feedstock. MAC has developed processes to achieve uniform mixing to eliminate even minute air pockets which could cause distortion or cracking during debinding and sintering. “Consistent particle size in the ceramic powder is critical”, said Manison, “Using sub-micron powders allows us to introduce smaller features into the part design”.

Mould Design and Injection Moulding
The Stourport CIM facility includes an impressive array of the latest injection moulding machines. MAC uses mould flow simulation and analysis to optimise both the part design and the mould design. This avoids expensive delays in production and allows adjustments to gate positions, wall thickness, etc. MAC uses sub-contractors for actual production of the moulds which tend to be in tool steels whereas the feeder screws are mostly in tungsten carbide to cope with the more abrasive ceramic in the feedstock. Maintenance of moulds is done in-house.

An important quality control innovation introduced at MAC is mould cavity pressure containment and control. Here the company uses pressure transducers inside the tool cavity to provide process control feedback as the feedstock flows into the cavity. Paul Manison stated that the pressure transducers are an ‘eye’ inside the cavity which helps control part weight and dimensions, and helps to eliminate flash, sinks, shorts and warp.

After moulding the ceramic parts are placed on refractory saggers and placed in racks in the large thermal debinding furnaces. Debinding can take several days and this stage must ensure complete binder removal before transfer of the debindersised parts to the top hat sintering furnaces operating at up to 1600C. Total shrinkage from the injection moulded part to the fully dense sintered ceramic part can be 20 to 30% so it is important to closely monitor the sintering cycle in order to achieve controlled shrinkage and the desired tolerances and shape. MAC advise that they can achieve sintered tolerances of ±0.3% of nominal and with batch-to-batch repeatability and Cpk’s in excess of 1.66.

Additional on-site facilities include SPC quality control inspection areas. Depending on the ceramic part in production, flatness and wall thickness is monitored along with surface finish. Post-sintering operations include grinding where required to ensure that all parts meet exact dimensional tolerances. Quality management is to ISO9001, 9002 and ENV 14002.

Markets and Applications
Since the opening of the new CIM facility just over two years ago, the company’s mission has been to improve dimensional tolerances to enable access to high end, high value markets. Paul Manison stated that technical successes have already resulted in a strong market position with only a limited number of suppliers worldwide able to compete with the quality and precision of CIM components made by MAC. Because of the nature of CIM components, with excellent compression and wear resistance, but relatively poor tensile strength, applications need to be carefully selected. Key potential markets for CIM components have been identified as aerospace, semiconductor processing, electronics, telecommunications, IT hardware, medical, automotive, thermal processing, industrial equipment, security and defence, power generation and distribution, domestic products and process control. The company recommends that as a general rule the minimum viable order for CIM parts is 10,000, primarily due to the high investment costs involved in injection moulding tools.

CIM Printhead Scores Notable Success
MAC teamed up Hewlett-Packard Co (HP) to provide a CIM solution for its latest scalable ink-jet technology. The alumina ceramic injection moulded printhead manufactured by Morgan allows for a great density of 3,900 print nozzles. As a result HP has been able to improve print speed and quality to create its fastest printing products to date. The ceramic product is designed to last the life of the printer, in contrast to standard disposable plastic printheads.

In this application CIM delivered a high precision, high performance component with excellent repeatability in high volume, contributing to a product that can print up to twice the speed of alternative colour laser printers. “Ceramic injection moulding offers significant process and raw material cost savings, compared to conventional methods of manufacturing complex parts,” said Paul Manison. “The capability of producing intricate and complex geometrical shapes to a high quality surface finish without further machining was key to the manufacture of the printheads. The ceramic printhead is produced as a net-shape sintered part with only double sided grinding required as a post-sintering operation in order to guarantee flatness and height tolerances. We were delighted to work with such a major international electronics manufacturer on the development of this innovative new printhead and support them with our ceramic expertise”. Ceramic has a superior material performance in this application. Its high hardness and mechanical strength, coupled with wear resistance, corrosion resistance, high working temperature and electrical insulation made it an ideal material.

Paul Manison acknowledged that as with all new manufacturing technologies, there has been an initial lack of awareness about the CIM process. “Design engineers need to be made aware of this technology’s potential to fully utilise CIM and continue the market growth”, he said. The success story of the CIM printhead is certainly drawing more attention to the technology, and MAC is confident of its role in being able to develop new applications.

_{For more information contact Paul Manison, Project Manager
Morgan Advanced Ceramics Ltd
Bewdley Road, Stourport-on-Severn
Worcestershire DY13 8QR, England
Direct Line +44 (0) 1299 872267
Fax +44 (0) 1299 872281
paul.manison@morganplc.com
www.morgantechnicalceramics.com}