Abstract: A 3D printer includes a gantry configured to move in a plane substantially parallel to a build plane. The system includes a platen configured to support a part being built in a layer by layer process, wherein the platen is configured to move in a direction substantially normal to the build plane. The system includes a head carriage carried by the gantry wherein the head carriage includes a first support member carrying a first retaining mechanism and a second support member carrying a second retailing mechanism. The first and second retaining mechanisms are both configured to receive and retain the print head or the additional equipment wherein both the removable print head and the removable additional equipment have substantially a same interface with the head carriage.