First extrusions with complex geometries

A team of researchers from the ORC have produced the first extrusions from their new high performance glass extrusion machine - a preform manufacturing system. This makes it possible to extrude geometries which would not be possible using other methods. Extrusion has been the preferred method for generating novel structures in a variety of glasses at the ORC for some time, and has underpinned a wide range of research.

One example of the extraordinary glass preforms which can be produced are those shaped like wagon wheels. Wagon wheel performs are characterised by air cladding around a central core, with very thin glass ‘webs’ (the ‘spokes’ of the wheel) supporting the core. The unusual structure of wagon wheels is not easy to produce but this new machine helps overcome these difficulties.

Previously the team used a hydraulic rig which was destroyed in the Mountbatten fire of October 2005. Its replacement offers a more controlled process whereby the speed of the extrusion and temperature can be monitored far more accurately. The extrusion rig is based on a materials testing machine made by The Testrometric Company, specially modified for this purpose. The rig is also fitted with a transparent guide tube which makes it possible to see what is happening to a preform rather than a metal tube which made it difficult to see the preform whilst it was being manufactured. Higher forces, higher temperatures, and extrusion in controlled atmosphere or vacuum are now possible. It takes approximately eight hours to produce a typical length of 150mm. In just its second extrusion the machine produced a preform which was longer, straighter and more uniform than any produced before.

This new system has made it possible for the team to surpass the stage they were at before the fire and offers huge potential for the development of more complex geometric shapes and different glasses which may present even more challenges. Ultimately these preforms will enable the creation of fibres with a whole host of different functionalities.

The work is supported by the EPSRC under Grant reference EP/D04555X/1.