Extrusion method and apparatus

Abstract

An extrusion method for forming a length of multimaterial extrudate includes providing a die; providing a container comprising a multimaterial feed material supply; effecting relative movement of the container towards the die so as to bring an axial surface of the die into contact with a rotating engagement surface of the supply of feed material; generating heat at the interface between the axial surface of the die and the rotating engagement surface of the multimaterial feed material supply so as to heat the at least two materials of the multimaterial feed material supply by the application of a contact pressure between the axial surface of the die and the rotating engagement surface of the feed material supply; pressing the heated multimaterial feed material supply through an orifice in the axial surface of the die so as to form a length of multimaterial extrudate in the extrusion channel.

1 . An extrusion method for forming a length of multimaterial extrudate, the method comprising:
 providing a die comprising a longitudinal axis;   providing a container comprising a multimaterial feed material supply comprising at least two materials,   the die and the container being configured such that the container is rotatable relative to the die about a rotation axis;   aligning the longitudinal axis of the die so as to be coincident with the rotation axis;   rotating the container relative to the die about the rotation axis;   effecting relative movement of the container towards the die so as to bring an axial surface of the die into contact with a rotating engagement surface of the supply of feed material;   generating heat at the interface between the axial surface of the die and the rotating engagement surface of the multimaterial feed material supply so as to heat the at least two materials of the multimaterial feed material supply by the application of a contact pressure between the axial surface of the die and the rotating engagement surface of the feed material supply so as to generate friction therebetween;   pressing the heated multimaterial feed material supply through an orifice in the axial surface of the die and into an extrusion channel in the die so as to form a length of multimaterial extrudate in the extrusion channel.   
     
     
         2 . The extrusion method according to  claim 1 , comprising providing further relative movement of the container in the direction towards the die so as to force the heated multimaterial feed material supply through the extrusion channel. 
     
     
         3 . The extrusion method according to  claim 1 , wherein the extrusion channel comprises an orifice arranged in axial surface of the die and
 wherein at least the orifice is located on the longitudinal axis of the die and preferably the extrusion channel extends at least partially along the longitudinal axis.   
     
     
         4 . The extrusion method according to  claim 1 , comprising providing the multimaterial feed material supply in the container, and aligning the multimaterial feed material supply with the rotation axis such that the arrangement of at least two materials in the multimaterial feed material supply is rotationally symmetrical about the rotation axis. 
     
     
         5 . The extrusion method according to  claim 1 , comprising providing a container comprising a multimaterial feed material supply comprising at least two metals and/or metal alloys. 
     
     
         6 . The extrusion method according to  claim 1 , comprising providing a container comprising a multimaterial feed material supply comprising copper as a first material and aluminium as a second material. 
     
     
         7 . The extrusion method according to  claim 1 , comprising rotating the container relative to the die about the rotation axis at a rotational speed of at least 90 rpm, in particular, when the cylindrical cavity  106  in the container has a cross section of 0.002 m 2 . 
     
     
         8 . The extrusion method according to  claim 1 , wherein the contact force for the generation of heat is at least 100 kN, preferably at least 150 kN, in particular, when the cylindrical cavity in the container has a cross section of 0.002 m 2 . 
     
     
         9 . The extrusion method according to  claim 1 , comprising plasticising a portion of the feed material supply at the engagement surface thereof by the generation of heat at the interface between the axial surface of the die and the rotating engagement surface, and flowing the plasticised portion of the feed material supply through the extrusion channel to form a length of multimaterial extrudate. 
     
     
         10 . The extrusion method according to  claim 1 , wherein the arrangement of the at least two materials in the cross-section of the formed length of multimaterial extrudate is the same as the arrangement of the at least two materials in the transverse cross-section of the multimaterial feed material supply in the container, preferably wherein the ratio between the radial thickness of the two materials in the multimaterial feed material supply and in the multimaterial extrudate is essentially equal. 
     
     
         11 . The extrusion method according to  claim 1 , comprising providing a cylindrical container comprising a multimaterial feed material supply located in a cylindrical cavity, and moving the container relatively towards the die such that the die is positioned at least partially inside the cylindrical cavity. 
     
     
         12 . The extrusion method according to  claim 11 , wherein the engagement surface of the die is substantially circular in cross-section and the diameter of the cylindrical cavity is the same as the diameter of the outer surface of the die adjacent to the engagement surface. 
     
     
         13 . An apparatus for providing a length of multimaterial extrudate, comprising:
 a die comprising a longitudinal axis and an axial surface comprising   an orifice to an extrusion channel therein;   a container comprising a multimaterial feed material supply comprising at least two materials, the container being rotatable rotating relative to the die about a rotation axis;   the longitudinal axis of the die and the rotation axis of the container being aligned so as to be coincident;   wherein the container and the die are configured such that during relative rotation of the container and the die about the rotation axis, and at least one of the die and the container are movable along the respective longitudinal axis and rotation axis so as to permit the axial surface of the die to be brought into contact with an engagement surface of the feed material supply;   wherein relative rotation of the container causes rotation of the engagement surface, such that contact with the axial surface of the die causes heating of the engagement surface, and the orifice in the axial surface of the die is configured to permit flow of heated multimaterial feed material supply therethrough and into the extrusion channel.   
     
     
         14 . The apparatus of  claim 13 , wherein the extrusion channel is parallel and coincident with the longitudinal axis of the stationary die. 
     
     
         15 . The apparatus of  claim 13 or 14 , wherein the multimaterial feed material supply is cylindrical in shape and comprises a first material in the shape of a cylinder, and a second material in the shape of a sleeve that is arranged around the cylindrical first material. 
     
     
         16 . The extrusion method according to  claim 1 , further comprising the implementation of a multimaterial extrudate as an electrical conductor or as a medical implant.