Abstract: The workpiece supporting bed of the present machine is provided with a ballast filled frame structure therebelow for forming a solid unitary support structure to dampen operational vibrations normally transmitted to the bed. A gantry extends above and across the workpiece supporting bed and includes a cast main beam formed of lightweight material to facilitate rapid movement, particularly rapid acceleration and deceleration during forward and rearward movement of the gantry. Integrally cast longitudinally and laterally extending ribs are provided on the main beam to provide additional stiffness and rigidity thereto. A single drive motor is provided to drive opposed sides of the gantry simultaneously and in accurate alignment with each other. A rearwardly extending housing is attached to the main frame and is filled with a lightweight plastic material for adding further rigidity and stiffness to the gantry, without substantially increasing the weight thereof.