A printing module configured to print a label on a curved surface of an article includes an expandable printing mechanism configured to be expanded to an open configuration for receiving the article or contracted to a closed configuration placing the curved surface in an operative position with respect to a print head and an article moving assembly configured to grasp and hold the article and effect relative movement between the curved surface and the print head. The printing mechanism includes contact elements, such as rollers, that contact or otherwise engage the article when the printing mechanism is in the closed configuration and maintain the curved surface in the operative position with respect to the print head during relative movement between the curved surface and the print head.