Method of calibrating a ribbon winding mechanism for a printing apparatus

A printing apparatus comprising a printing station at which during a printing operation, there is relative movement between a print head and a first length of a ribbon during which print medium is transferred from the first length of the ribbon onto a substrate, and the ribbon is subsequently advanced a desired amount to present a second length of the ribbon at the printing station for use in a further printing operation, ribbon movement being achieved by a winding mechanism comprising a supply spool and a take-up spool with there being a ribbon path between the supply and take-up spools through the printing station, the winding mechanism further comprising a motive device to cause ribbon to be moved along the ribbon feed path and wound onto the take-up spool, there being a sensor to sense movement of the ribbon a the ribbon is wound onto the take-up spool and to provide a signal to a controller in response, wherein the controller is adapted, prior to a printing operation, to operate the motive device so that the take-up spool is rotated a predetermined amount whilst the sensor senses ribbon movement along the ribbon feed path, and to determine from the signal received from the sensor the amount to rotate the take-up spool to advance the ribbon the desired amount during advancement of the ribbon after printing in a subsequent printing operation.