Thermal barrier for tool port into heated build chamber of 3d printer

A method of swapping print heads during a build job in a 3D printer that extrudes material into a heated build chamber, the method comprising:

• providing an x-y gantry mounted on top of the build chamber and comprising a x-bridge spanning the build chamber, a print head carriage providing a tool mount for removable installation of one or more print heads and configured for back-and-forth movement along the x-bridge, wherein the x-y gantry is configured to move the carriage in an x-y plane above the build chamber, an upward-facing tool tray coupled to or integral with the carriage and having an open bottom providing a tool port for accessing the heated build chamber, an x-axis deformable thermal insulator spanning a length of the x-bridge and coupled to opposite ends of the tray and or the carriage so as to expand and contract with the back-and-forth movement of the carriage along the x-bridge, the x-axis deformable thermal insulator thereby covering a portion of the build chamber and forming part of the ceiling, wherein the x-axis thermal barrier comprises an aperture configured to expand as a working end of a first print head passes therethrough and configured to contract about the print head once the working end passes through the thermal barrier;
• moving the working end of the first print head through the thermal barrier, thereby causing the tool port to be substantially closed;
• and
• lifting the first print head from the heated build chamber by passing the working end through the thermal barrier and once the working end is removed from the aperture for a tool swap, the aperture contracts to an area that is less than a maximum cross-sectional area of the working end.