Printhead Alignment Correction for Print Media Thickness

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Solution Overview

Problem

Misalignment of a printhead in printers, particularly during bidirectional printing, leads to a mismatch between drops fired during forward and reverse travel, affecting the quality of the printed image.

Innovation Solution

The printer employs an alignment module that determines an alignment value for each printhead based on the difference in height from the calibration position, using a method that calculates a correction to the calibration alignment value, which is then used to adjust the firing times of the nozzles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the printhead height is adjusted from the calibration position, then the printer can accommodate different print media thicknesses, but the printhead alignment deteriorates causing mismatch between drops fired during forward and reverse travel

Engineering Contradiction:

Improveaccommodation of different print media thicknessesVSAvoidprinthead alignment

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The system changes the alignment parameter (firing time offset) based on the printhead height position. When the printhead is raised or lowered from calibration position, the controller calculates a corrected alignment value based on the height difference and applies it to adjust the firing times, maintaining drop alignment across different heights

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The alignment value is made dynamic rather than static. The system continuously monitors printhead height position and dynamically adjusts the alignment parameter in real-time based on the current height, allowing the alignment to adapt as the printhead moves between different printing positions

Inventive Principle:

Principle #15Dynamics

2Manufacturing precision

If recalibration is performed to restore alignment after height adjustment, then printhead alignment is restored, but printing materials are wasted and productivity decreases

Engineering Contradiction:

Improveprinthead alignmentVSAvoidprinting efficiency

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The system performs preliminary calculation of the corrected alignment value based on the height difference before actual printing occurs. By pre-calculating the required alignment adjustment, the system avoids the need for time-consuming recalibration procedures and material waste associated with test printing

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The physical recalibration process (which requires mechanical test printing and manual adjustment) is replaced by a computational method. The controller calculates the corrected alignment value using the measured height difference and applies it electronically, substituting the mechanical recalibration process with a mathematical calculation and electronic parameter adjustment

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS12233644B2Determining alignment of a printhead

Publication Date: 2025.02.25 HEWLETT PACKARD DEVELOPMENT COMPANY LP

AI summary

A method is described in which a difference in height is determined between a current position and a calibration position of a printhead of a printer. An alignment value for the printhead is then determined based on the difference.