An apparatus for layered manufacture of a three-dimensional product includes a build chamber having a window, a build platform within the build chamber, a calibration device that is physically separated from the build chamber, an optical system including a beam source and a scanning apparatus, and a mobile base. The mobile base is configured to position the scanning apparatus at two spaced part positions including a (1) production position and a (2) calibration position. At the production position the scanning apparatus is configured to receive an energy beam from the beam source and to reflect and scan the energy beam through the window and to a build surface over the build platform to create a layer of the three-dimensional product. At the calibration position the scanning apparatus is configured to reflect the energy beam to the calibration device but not through the window.