A method of ink jet printing UV curable ink from an ink jet printhead onto a rigid substrate formed of a material that has a tendency to at least temporarily deform in the direction of printhead if exposed to radiant curing energy while at a printing station, the method comprising: moving a printhead carriage having an ink jet printhead thereon approximately parallel to a substrate at a printing station; jetting ink from the head onto the surface of a substrate; providing at least one cold UV curing assembly on the carriage, adjacent to and moveable with the printhead, and oriented to direct UV energy onto the surface of the substrate at the printing station sufficiently close to where ink is being jetted onto the surface to freeze dots of the jetted ink on the surface; and the cold UV assembly being effective to impinge sufficient UV light on the ink to substantially cure the ink without impinging radiation that would heat the substrate so as to deform it, even temporarily, while at the printing station. view more

The method of claim 1 further comprising:</claim-text> adjusting the distance from the printhead to the substrate to position the head at a predetermined distance from the surface of the substrate on which ink is jetted from the head.

The method of claim 1 further comprising:</claim-text> adjusting the distance of the UV light from a light source to focus the UV light onto the surface that bears the jetted ink.

The method of claim 1 further comprising:</claim-text> adjusting the focal length from a source of the UV light on the surface that bears the jetted ink to maintain the focus of UV light thereon as distance from the source to the surface varies.

The method of claim 1 further comprising:</claim-text> sensing the position of the surface of the substrate relative to the carriage; and adjusting the distance from the printhead to the plane of the substrate in response to said sensing.

The method of claim 1 further comprising:</claim-text> the providing of at least one cold UV curing assembly on the carriage includes providing at least two cold UV curing heads, adjacent to the printhead, one on each side thereof, and moveable with, and oriented to direct UV energy onto the surface of the substrate at the printing station sufficiently close to where ink is being jetted onto the surface to freeze dots of the jetted ink on the surface; the cold UV curing heads being energizable alternately to direct UV energy onto the surface of the substrate on the trailing side of the carriage. view more

An apparatus for printing on surfaces of substrates with UV curable ink from an ink jet printhead onto a rigid substrate formed of a material that has a tendency to at least temporarily deform in the direction of printhead if exposed to radiant curing energy while at a printing station comprising: a substrate support defining a substrate supporting plane at a printing station; a printhead track extending parallel to the plane having a printhead carriage moveable thereon; at least one ink jet printhead on the carriage; at least one UV curing head on the carriage, adjacent to and moveable with the printhead, and sufficiently close to the ink jet printhead to freeze dots of ink in position on the substrate when jetted thereon from the printhead; and the UV curing head being configured to emit sufficient UV energy to substantially cure the ink jetted onto the substrate without heating and thermally deforming, even temporarily while at the printing station, a substrate formed of such a material, so that the surface of the material being printed upon does not move from the plane for printing. view more

The apparatus of claim 10 wherein:</claim-text> the at least one UV curing head on the carriage includes at least two UV curing heads on the carriage, one on each side of the printhead, sufficiently close to the ink jet printhead to freeze dots of n position on the substrate when jetted thereon from the printhead; and the apparatus further comprising a controller operative to control the printhead to print in a bidirectional scanning motion on the substrate, and to activate the UV curing heads alternately to expose jetted ink on the trailing side of the printhead. view more