Curved Printhead CTE Molding for Print Alignment

Solution Overview

Problem

In printing devices, the collinear arrangement of fluid ejection dies leads to variations in distance and angle relative to the print medium, causing defects such as blurring, stretching, and distortions due to differences in travel time and positioning, resulting in suboptimal print quality.

Innovation Solution

A curved printhead is designed with fluid ejection dies overmolded using epoxy mold compounds with varying coefficients of thermal expansion (CTE), creating a non-planar arrangement that matches the curvature of the print medium, ensuring each die remains equidistant and maintaining optimal printing alignment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a collinear arrangement of fluid ejection dies is used, then the device structure is simple and manufacturing is easy, but the print quality deteriorates due to variations in distance and angle relative to the print medium

Engineering Contradiction:

Improveease of manufactureVSAvoidprint quality

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent applies curvature to the printhead by arranging fluid ejection dies along a curved surface rather than a straight line. The dies are positioned on a cylindrical or arc-shaped substrate, creating a curved array that matches the curvature of the print medium path. This curvature allows all dies to maintain equidistant spacing from the print medium while moving through the printing zone, eliminating the distance and angle variations that cause print defects in collinear arrangements.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Manufacturing precision

If a curved arrangement of fluid ejection dies is used, then print quality is improved by maintaining consistent spacing, but the device complexity increases

Engineering Contradiction:

Improveprint qualityVSAvoiddevice complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent merges the curvature function into the substrate itself by forming the fluid ejection dies on a curved or cylindrical surface. Rather than adding separate mechanisms to maintain curvature, the substrate is designed with the curved geometry integrated into its structure. The dies, fluid channels, and support structures are all conformally arranged on this curved surface, combining multiple functions into a single integrated component that reduces overall device complexity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent changes the geometric parameter of the die array from linear to curved by modifying the substrate shape. This parameter change transforms the spatial arrangement of all components simultaneously - the dies are positioned along an arc, the fluid channels follow the curved path, and the entire assembly maintains a constant radius of curvature. This single parameter change propagates through the design, simplifying the curvature implementation while achieving consistent die-to-medium spacing.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If collinear dies are used, then the device structure is simple, but print defects occur due to variations in travel time and positioning

Engineering Contradiction:

Improvedevice structureVSAvoidprint consistency

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent applies curvature to the printhead by arranging fluid ejection dies along a curved surface rather than a straight line. The dies are positioned on a cylindrical or arc-shaped substrate, creating a curved array that matches the curvature of the print medium path. This curvature allows all dies to maintain equidistant spacing from the print medium while moving through the printing zone, eliminating the distance and angle variations that cause print defects in collinear arrangements.

Inventive Principle:

Principle #14Spheroidality (Curvature)

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

The curved printhead minimizes print defects by maintaining consistent die-to-medium spacing, enhancing print quality, reducing manufacturing costs, and allowing for tighter head-to-paper control and a wider print zone.

Implementation Method 1

Each of the fluid ejection dies and the EMC include a coefficient of thermal expansion (CTE). The combination of the CTE of the fluid ejection dies and the CTE of the at least one layer of EMC defines a curve within the curved printhead.

Methodology Applied

Scientific EffectCoefficient of thermal expansion (CTE): Thermal Expansion

Data Source

PatentUS11351787B2Curved fluid ejection devices

Publication Date: 2022.06.07 HEWLETT PACKARD DEVELOPMENT COMPANY LP

AI summary

A curved fluid ejection device may include a plurality of fluid ejection dies overmolded with at least one layer of epoxy mold compound (EMC). Each of the fluid ejection dies and the EMC include a coefficient of thermal expansion (CTE). The combination of the CTE of the fluid ejection dies and the CTE of the at least one layer of EMC defines a curve within the curved fluid ejection device.