Filament for extrusion-based additive manufacturing system

Abstract

A filament is fed to an extrusion head. The filament has a semi-crystalline polymeric reinforcement portion and a polymeric matrix portion. The reinforcement and matrix portions run continuously along a length of the filament. The reinforcement portion has a higher melting point and a higher crystallinity than the matrix portion. The temperature of the filament is raised in the extrusion head above the melting point of the matrix portion but below the melting point of the reinforcement portion so that the matrix portion of the filament melts within the extrusion head, thereby forming a partially molten filament within the extrusion head. The partially molten filament is extruded from the extrusion head onto a substrate, the reinforcement portion of the partially molten filament remaining in a semi-crystalline state as it is extruded from the extrusion head. Relative movement is generated between the extrusion head and the substrate as the partially molten filament is extruded onto the substrate in order to form an extruded line on the substrate. The matrix portion of the extruded line solidifies after the extruded line has been formed on the substrate.

1 . A filament for use in an extrusion-based additive manufacturing method, the filament comprising:
 a semi-crystalline polymeric reinforcement portion which runs continuously along a length of the filament; and   a solid polymeric matrix portion which runs continuously along a length of the filament,   wherein the reinforcement portion has a higher melting point and a higher crystallinity than the matrix portion.   
     
     
         2 . The filament of  claim 1  wherein the reinforcement portion and the matrix portion are intertwined with each other so that they both follow tortuous paths along the length of the filament. 
     
     
         3 . The filament of  claim 2  wherein the reinforcement portion and the matrix portion are twisted together so that they both follow helical paths along the length of the filament. 
     
     
         4 . The filament of  claim 1  wherein the reinforcement portion comprises a ferroelectric polymer. 
     
     
         5 . The filament of  claim 1  wherein the reinforcement portion comprises polyvinylidene fluoride. 
     
     
         6 . The filament of  claim 1  wherein the matrix portion is formed from the same polymer as the reinforcement portion, with different molecular weights. 
     
     
         7 . The filament of  claim 1  wherein a polymer forming the reinforcement portion has a higher molecular weight than a polymer forming the matrix portion. 
     
     
         8 . The filament of  claim 1  wherein the matrix portion has a melting point which is below 180° C. 
     
     
         9 . The filament of  claim 1  wherein the reinforcement portion has a melting point which is below 200° C. 
     
     
         10 . The filament of  claim 1  wherein a difference in melting points between the reinforcement portion and the matrix portion is less than 15° C. 
     
     
         11 . The filament of  claim 10  wherein a difference in melting points between the reinforcement portion and the matrix portion is greater than 2° C. and less than 15° C. 
     
     
         12 . The filament of  claim 10  wherein a difference in melting points between the reinforcement portion and the matrix portion is greater than 5° C. and less than 15° C. 
     
     
         13 . The filament of  claim 1  wherein a difference in melting points between the reinforcement portion and the matrix portion is less than 10° C. 
     
     
         14 . The filament of  claim 13  wherein a difference in melting points between the reinforcement portion and the matrix portion is greater than 2° C. and less than 10° C. 
     
     
         15 . The filament of  claim 13  wherein a difference in melting points between the reinforcement portion and the matrix portion is greater than 5° C. and less than 10° C. 
     
     
         16 . The filament of  claim 1  wherein the reinforcement portion occupies more than 60% of a volume of the filament. 
     
     
         17 . The filament of  claim 1  wherein the reinforcement portion occupies less than 91% of a volume of the filament. 
     
     
         18 . The filament of  claim 1  wherein the reinforcement portion comprises a plurality of fibres. 
     
     
         19 . The filament of  claim 1  wherein the reinforcement portion has a yield strength which is greater than 500 MPa. 
     
     
         20 . The filament of  claim 1  wherein the reinforcement portion comprises at least one reinforcement fibre in which more than 50% of the fibre by volume comprises crystals aligned within 1° of being parallel with a length of the fibre.