The invention provides a printer comprising an exchange station by which a printer module of a multifunction 3D printer can be attached and detached. The printer module is electromagnetically or mechanically attached to the exchange station to perform a printing operation. The multifunction 3D printer supports the printer module steadily and stably.

Embodiments relate to a flex hub mount for a circular brush assembly. The flex hub mount includes a disc having a disc upper surface and a disc lower surface, a disc aperture, and a disc rib extending from the disc upper surface. The flex hub mount includes a flex pad having a flex pad aperture. The flex pad is dimensioned to rest on a portion of the disc upper surface between the disc aperture and the disc rib. The flex pad aperture and the disc aperture are in vertical registry. The flex hub mount includes a plug disposed within the disc aperture. The plug is configured to connect or be held adjacent to the flex pad. The plug and the flex pad are configured to close the disc aperture such that the disc aperture is sealed.