Method and device for forming microstructured fibre

A method for extruding an extrudable material to form an extruded member, the method comprising:

• introducing a billet of material into an inlet chamber of a die, the billet of material comprising a solid polymer or glass material;
• heating the billet of material in the inlet chamber to a predetermined temperature to form extrudable material;
• initially forcing the extrudable material from the inlet chamber through a barrier member into an open ended extrudate forming chamber of the die, wherein the barrier member is located between the inlet chamber and the extrudate forming chamber in the direction of extrusion and comprises a feed hole plate having a plurality of spaced apart feed channels each extending independently without flow communication through the barrier member and at least one passage forming member extending from the feed hole plate in a direction of extrusion into the open ended extrudate forming chamber, and
• continuing to force the extrudable material at a ram speed from the inlet chamber into the open ended extrudate forming chamber to form the extruded member, wherein the extrudable material is caused to substantially flow about the passage forming member on exit from the spaced apart feed channels to form at least one corresponding passage in the extruded member.