Bidirectional Printhead Segmentation for Missing Nozzle Compensation

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Solution Overview

Problem

Conventional inkjet printers are unable to effectively minimize printing defects caused by missing or nonfunctional nozzles, leading to suboptimal print quality due to inconsistent ink drop distribution and color order issues.

Innovation Solution

A method involving a printhead that traverses a media sheet in two directions, with different portions of the printhead aligning and printing in each direction to compensate for missing nozzles by adjusting the media sheet relative to the printhead by an index distance, ensuring that each area is printed twice by different sets of nozzles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional inkjet printers use single-pass or traditional multi-pass printing, then print speed and basic functionality are maintained, but printing defects occur due to missing nozzles causing inconsistent ink drop distribution and color order issues

Engineering Contradiction:

Improveprint quality consistencyVSAvoidprinting defects from missing nozzles

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The printhead is divided into multiple segments (first portion and second portion), each responsible for printing different portions of the media sheet. This segmentation allows the system to compensate for missing nozzles in one segment by using the other segment to print the same area, thereby maintaining print quality consistency despite nozzle failures.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The printing process is performed in periodic passes, where the printhead traverses the media sheet multiple times in alternating directions. Each pass uses different portions of the printhead, creating a periodic pattern of printing that ensures redundant coverage and compensates for missing nozzles across multiple cycles.

Inventive Principle:

Principle #19Periodic action

2Area of stationary object

If the printhead traverses the media sheet in multiple passes with bidirectional printing, then coverage area increases, but dry-time banding defects occur due to variable drying times on different sides of printed regions

Engineering Contradiction:

Improveprinted area coverageVSAvoidcolor consistency

Core Design Contradiction:

Area of stationary objectVSManufacturing precision

Solution Approach 1:

The printhead traverses the media sheet in opposite directions during different passes. By inverting the printing direction and using different portions of the printhead for each direction, the system ensures that both sides of any given region receive ink at similar times, eliminating the variable drying times that cause dry-time banding defects.

Inventive Principle:

Principle #13The other way round (Inversion)

3Reliability

If redundant ink channels are added to achieve consistent color order in bidirectional printing, then color-order defects are eliminated, but device complexity and cost increase

Engineering Contradiction:

Improvecolor order consistencyVSAvoidnumber of ink channels

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Instead of using static redundant ink channels, the system dynamically assigns different portions of the existing printhead to different printing tasks based on the pass direction. The first portion prints during traversal in the first direction, while the second portion prints during traversal in the opposite direction, providing dynamic compensation for missing nozzles without adding physical redundancy to the ink channel structure.

Inventive Principle:

Principle #15Dynamics

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach significantly reduces printing defects associated with missing nozzles by ensuring that each row of the media sheet is printed with two different sets of nozzles, thereby maintaining print quality and consistency.

Implementation Method 1

Each nozzle may be 'fired' by means of activation resistors, such that a corresponding activation resistor of the nozzle heats the ink in the corresponding bubble chamber of the nozzle

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

The ink heats up to form an ink bubble in the bubble chamber. The ink bubble is expelled out of the nozzle on to a media sheet

Methodology Applied

Scientific EffectThermal expansion and bubble formation: Phase Change

Data Source

PatentUS8210631B2Method for minimizing printing defects due to missing nozzle in media processing device

Publication Date: 2012.07.03 BRADY WORLDWIDE INC

AI summary

Disclosed is a method for printing a media sheet in a media processing device. The method includes aligning a first portion of a printhead of the media processing device to a print area of the media sheet. The method further includes printing the print area of the media sheet by traversing the printhead over the print area in a first direction. The printing is performed by the first portion. Further, the method includes aligning a second portion of the printhead to the print area by adjusting the media sheet relative to the printhead by an index distance in a direction perpendicular to the first direction. Thereafter, the method includes reprinting the print area by traversing the printhead over the print area in a second direction opposite to the first direction. The reprinting is performed by the second portion.