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 ; <EOS>