US 5,889,534 A · Calibration and registration method for manufacturing a drum-based printing system

Abstract

The present invention relates to the a method usable in the field of printing, and in particular to a method of characterizing a drum-based digital print engine so that each of a plurality of ink droplets propelled toward a common picture element location, or pixel, of a print media coupled to an exterior surface of a rotating drum member precisely reaches the same pixel location irregardless of slight variations in portions of the surface of the drum. In a preferred embodiment, a drum based printing system contains eight print heads mounted on an axially driven carriage assembly and arranged in two rows of four such that no two print heads prints upon a common print swath at any given time, and each row of print heads is further oriented rotationally around a portion of the circumference of the drum member. All print heads operate relatively independently of fixed firing locations, and instead operate based on a first firing printing head so that each subsequent print heads fire only after a predetermined delay due simply to its rotational and axial displacement from the first print head. Slight variations in the surface of the drum and non concentric alignment of a rotation sensor coupled to the axis of rotation of the drum are compensated during initial assembly of the print engine. In one embodiment, this technique allows implementation of effective and simple calibration process for a four hundred nozzle wide format ink jet digital print engine during printing by an end user.

Claims5

Dependent claims

A method of calibrating a drum-based print engine, including the steps of characterizing the positional interplay among an exterior print media-bearing surface with respect to a plurality of print heads and compensating for non-concentric alignment of a rotation sensor coupled to the axis of rotation of the drum member, comprising the steps of:

attaching a sheet of printing medium to the exterior surface of a cylindrical drum member;
rotating a cylindrical drum member about its axis at a preselected printing velocity;
printing at least two calibration patterns for each discrete ink-dispensing nozzle, one for axial registration a second pattern for rotational registration;
manually comparing the calibration patterns;
manually entering a value corresponding to a best fit into a computer memory;
adjusting a controlled firing sequence command so that each ink-dispensing nozzle prints at a preselected location upon a media coupled to the drum;
accelerating the rotation of the drum member to a constant velocity in excess of the first preselected printing velocity;
recording a timing signal from a rotary encoder coupled to the axis of rotation of the drum member, wherein the timing signal consists of a timed repeating sequence of on and off signals of varying period;
comparing a difference in a first timing signal to an immediately subsequent timing signal over a plurality of revolutions of the drum member;
calculating a best curve fit of the difference in timing signals per rotation of the drum member;
applying the best curve fit to a print head control circuitry so that for each rotation of the drum member a print head at least one nozzle of an ink jet print head emits ink at a precise location.

8 more elements

Dependencies are inferred from the claim text.

Calibration and registration method for manufacturing a drum-based printing system

Life of this patent

Calibration and registration method for manufacturing a drum-based printing system

Life of this patent

Abstract

Claims5