Abstract: A thermal printing apparatus for printing graphic images on sheet material, such as a vinyl sheet, utilizes a platen drive to move the sheet material between a roller platen and thermal print head. The thermal print head presses the sheet material into engagement with the roller platen along a linear zone of contact, and a drive motor is drivingly connected to the roller platen through a series of drive gears to rotatably drive the roller platen, and in turn move the sheet material between the platen and print head. A pair of registration sprockets are mounted on opposite ends of a common sprocket shaft, and engage corresponding feed holes formed in the marginal edges of the sheet material. The registration sprockets guide and steer the sheet material as it is driven between the roller platen and the print head, and substantially prevent buckling or like distortion of the sheet material.