An extruder comprising: a feed tube ; a filament inlet arranged for feeding filament from outside the extruder into the feed tube ; a heat sink below the filament inlet and surrounding a portion of the feed tube ; a heating block below the heat sink and surrounding a portion of the feed tube ; a heat guard surrounding at least a portion of the heating block and including one or more outlet slots ; a nozzle on a distal end of the feed tube and protruding out of the heating block ; a blower with an air inlet and an air exit ; at least one baffle ; and a channel that is positioned below the air exit of the blower such that air flow from the air exit of the blower enters the channel and that is divided by the at least one baffle into at least two air passages , each of the at least two air passages with its own respective inlet, wherein: a first air passage of the at least two air passages is configured to direct a portion of the air flow across the heat sink and through an outlet ; and a second air passage of the at least two air passages is configured to direct another portion of the air flow towards and through the one or more outlet slots in the heat guard and across the nozzle ; characterized by comprising a louver, wherein, for the at least two air passages , the louver is configured to at least partially close the respective inlet to the respective air passage , wherein the louver is configured to be shifted into a plurality of positions, each corresponding to a different respective ratio of an amount of the air flow being directed into the first air passage to an amount of the air flow being directed into the second air passage . a feed tube ; a filament inlet arranged for feeding filament from outside the extruder into the feed tube ; a heat sink below the filament inlet and surrounding a portion of the feed tube ; a heating block below the heat sink and surrounding a portion of the feed tube ; a heat guard surrounding at least a portion of the heating block and including one or more outlet slots ; a nozzle on a distal end of the feed tube and protruding out of the heating block ; a blower with an air inlet and an air exit ; at least one baffle ; and a channel that is positioned below the air exit of the blower such that air flow from the air exit of the blower enters the channel and that is divided by the at least one baffle into at least two air passages , each of the at least two air passages with its own respective inlet, wherein: a first air passage of the at least two air passages is configured to direct a portion of the air flow across the heat sink and through an outlet ; and a second air passage of the at least two air passages is configured to direct another portion of the air flow towards and through the one or more outlet slots in the heat guard and across the nozzle ; a first air passage of the at least two air passages is configured to direct a portion of the air flow across the heat sink and through an outlet ; and a second air passage of the at least two air passages is configured to direct another portion of the air flow towards and through the one or more outlet slots in the heat guard and across the nozzle ; characterized by comprising a louver, wherein, for the at least two air passages , the louver is configured to at least partially close the respective inlet to the respective air passage , wherein the louver is configured to be shifted into a plurality of positions, each corresponding to a different respective ratio of an amount of the air flow being directed into the first air passage to an amount of the air flow being directed into the second air passage . <EOS>