System and method for compensating for registration errors arising from heated rollers in a moving web printing system

A system for operating printhead firing in a web printing system comprising:

• a first roller configured to rotate with a web moving through a print zone of a web printing system;
• a first encoder mounted proximate the first roller to generate a signal corresponding to an angular velocity of the first roller;
• a first temperature sensor mounted proximate the first roller to generate a signal corresponding to a temperature of the first roller;
• a first printhead positioned in the print zone proximate the web;
• and
• a controller coupled to the first encoder, the first temperature sensor, and the first printhead, the controller being configured to identify a distance change in a first diameter of the first roller and to compute a web velocity for the web moving through the print zone with reference to the distance change in the first diameter of the first roller, and the controller also being configured to generate a firing signal to the printhead to eject ink onto the web at a position corresponding to the computed web velocity.

A method for computing a thermal coefficient of expansion for a roller in a print zone of a web printing system comprising:

• printing a predetermined pattern onto a first portion of a moving web with a first printhead as the web moves through a print zone of a web printing system while a temperature of a first roller in the print zone is at a first temperature;
• generating image data corresponding to the printed predetermined pattern after the first portion of the moving web exits the print zone;
• printing the predetermined pattern onto a second portion of the moving web with the first printhead as the web moves through the print zone of the web printing system while a temperature of the first roller in the print zone is at a second temperature;
• generating image data corresponding to the printed predetermined pattern after the second portion of the moving web exits the print zone;
• and
• identifying a coefficient of thermal expansion from a first diameter for the first roller, a displacement between the predetermined pattern on the first portion of the web and the predetermined pattern on the second portion of the web, and a temperature difference between the first temperature and the second temperature.