Abstract: A positioning device includes a gantry robot and an elevator unit. The gantry robot includes a head assembly, a work-space spaced below the head assembly for receiving at least one tray and a device for moving the head assembly in the X, Y and Z directions. The gantry robot further includes a device for scanning the work-space. The elevator unit has a plurality of shelves arranged in a series one above another. Each shelf is adapted to receive at least one tray and the shelves are movable in the Z direction. A device for moving a tray between the elevator unit and the work-space is included. A control system for controlling the movement of the head assembly in the X, Y and Z direction, for controlling the movement of the shelves in the Z direction and for controlling the tray moving device is operably connected to the gantry robot and the elevator unit.