A 3D printer (100) including an expandable build chamber (102), a print bed (122), and a print head (124) is disclosed. The expandable build chamber (102) is defined by a plurality of stationary walls (104) and an adjustable wall (106) enclosing an open interior (116) having an open interior volume. The print bed (122) is configured to receive the feedstock material from the print head (124). The print bed (122) is disposed within the open interior (116). The print head (124) is configured to deposit the feedstock material onto the print bed (122). The print head (124) is disposed within the open interior (116). The adjustable wall (106) is configured to move away from the open interior (116) to increase the open interior volume as the print head (124) deposits the feedstock material onto the print bed (122) while maintaining isolation of the open interior (116) from the ambient environment.