An apparatus for extruding plastic material, the apparatus comprising: - a feeding portion; - a melting portion in communication with the feeding portion and configured to transmit heat into material received from the feeding portion; - an output die in communication with the melting portion to permit extrusion of material received from the melting portion; and - the melting portion comprising: - a melting barrel having an inner surface defining a melting chamber in communication with the feeding portion; and - a melting insert inside of the melting chamber, the melting insert comprising an outer surface, the outer surface of the melting insert comprising one or more open-ended channels formed therein and extending in a flow direction of the melting barrel, the one or more channels and the inner surface of the melting barrel defining corresponding one or more through flow passages for delivering material toward the output die, wherein: the outer surface of the melting insert is at least partially in contact with the inner surface of the melting barrel; or the one or more open-ended channels comprise a plurality of open-ended channels separated by intermediate outer surface portions each cooperating with the inner surface of the melting barrel to provide a direct thermal conduction path between the melting barrel and the melting insert; and wherein the melting insert has a solid core and a tapered leading end; characterized in that the apparatus further comprises a thermal insulator disposed between the feeding portion and the melting portion. - a feeding portion; - a melting portion in communication with the feeding portion and configured to transmit heat into material received from the feeding portion; - an output die in communication with the melting portion to permit extrusion of material received from the melting portion; and - the melting portion comprising: - a melting barrel having an inner surface defining a melting chamber in communication with the feeding portion; and - a melting insert inside of the melting chamber, the melting insert comprising an outer surface, the outer surface of the melting insert comprising one or more open-ended channels formed therein and extending in a flow direction of the melting barrel, the one or more channels and the inner surface of the melting barrel defining corresponding one or more through flow passages for delivering material toward the output die, wherein: the outer surface of the melting insert is at least partially in contact with the inner surface of the melting barrel; or the one or more open-ended channels comprise a plurality of open-ended channels separated by intermediate outer surface portions each cooperating with the inner surface of the melting barrel to provide a direct thermal conduction path between the melting barrel and the melting insert; and wherein the melting insert has a solid core and a tapered leading end; - a melting barrel having an inner surface defining a melting chamber in communication with the feeding portion; and - a melting insert inside of the melting chamber, the melting insert comprising an outer surface, the outer surface of the melting insert comprising one or more open-ended channels formed therein and extending in a flow direction of the melting barrel, the one or more channels and the inner surface of the melting barrel defining corresponding one or more through flow passages for delivering material toward the output die, the outer surface of the melting insert is at least partially in contact with the inner surface of the melting barrel; or the one or more open-ended channels comprise a plurality of open-ended channels separated by intermediate outer surface portions each cooperating with the inner surface of the melting barrel to provide a direct thermal conduction path between the melting barrel and the melting insert; and wherein the melting insert has a solid core and a tapered leading end;