Thermal transfer printing apparatus comprising: ▪ an endless ribbon comprising an inner face and an outer face; ▪ a coating device to coat the endless ribbon with ink on a coating zone, ▪ a printhead to print by thermal transfer a substrate with a part of the ink coated on the endless ribbon on a printing zone, ▪ a conveyor system (10, 11) to support and transport the endless ribbon along a path from the coating device to the printhead and from the printhead to the coating device; characterised in that the thermal transfer printing apparatus further comprises ▪ a pre-printing buffer comprising at least two moving rollers to support the coated ribbon during its transport from the coating device to the printhead: a first moving roller arranged to support the inner face of the endless ribbon and a second moving roller arranged to support the outer face of the endless ribbon; ▪ a post-printing buffer comprising at least two moving rollers (71, 73) to support the ribbon during its transport from the printhead to the coating device: a third moving roller arranged to support the inner face of the endless ribbon and a fourth moving roller arranged to support the outer face of the endless ribbon; wherein each moving roller (71, 73, 81, 83) is movable along a predefined trajectory (72, 82) in a plane sensibly perpendicular to the longitudinal axis of the moving rollers (71, 73, 81, 83); ▪ a first controller (CALC) configured to: ▪ control the movement of the first moving roller and second moving rollers along their predefined trajectory to increase or decrease the length of the coated ribbon path from the coating device to the printhead; and ▪ control the movement of the third moving roller and the fourth moving rollers along their predefined trajectory to increase or decrease the length of the ribbon path after printing from the printhead to the coating device. ▪ an endless ribbon comprising an inner face and an outer face; ▪ a coating device to coat the endless ribbon with ink on a coating zone, ▪ a printhead to print by thermal transfer a substrate with a part of the ink coated on the endless ribbon on a printing zone, ▪ a conveyor system (10, 11) to support and transport the endless ribbon along a path from the coating device to the printhead and from the printhead to the coating device; characterised in that the thermal transfer printing apparatus further comprises ▪ a pre-printing buffer comprising at least two moving rollers to support the coated ribbon during its transport from the coating device to the printhead: a first moving roller arranged to support the inner face of the endless ribbon and a second moving roller arranged to support the outer face of the endless ribbon; ▪ a post-printing buffer comprising at least two moving rollers (71, 73) to support the ribbon during its transport from the printhead to the coating device: a third moving roller arranged to support the inner face of the endless ribbon and a fourth moving roller arranged to support the outer face of the endless ribbon; wherein each moving roller (71, 73, 81, 83) is movable along a predefined trajectory (72, 82) in a plane sensibly perpendicular to the longitudinal axis of the moving rollers (71, 73, 81, 83); ▪ a first controller (CALC) configured to: ▪ control the movement of the first moving roller and second moving rollers along their predefined trajectory to increase or decrease the length of the coated ribbon path from the coating device to the printhead; and ▪ control the movement of the third moving roller and the fourth moving rollers along their predefined trajectory to increase or decrease the length of the ribbon path after printing from the printhead to the coating device. ▪ control the movement of the first moving roller and second moving rollers along their predefined trajectory to increase or decrease the length of the coated ribbon path from the coating device to the printhead; and ▪ control the movement of the third moving roller and the fourth moving rollers along their predefined trajectory to increase or decrease the length of the ribbon path after printing from the printhead to the coating device.