Inkjet Nozzle Joint Ejection Control for White Streak Suppression
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Solution Overview
Problem
Inkjet printing apparatuses with vertically arranged nozzles experience pressure differences between nozzles due to hydraulic head differentials, leading to varying drop distances and image quality deterioration at joint portions between inkjet heads, especially when printing on vertically oriented surfaces.
Innovation Solution
A droplet ejection control apparatus that adjusts the ejection amount and dot data for nozzles at joint portions between vertically adjacent nozzle groups, reducing ejection from upper nozzles and increasing it from lower nozzles to equalize drop distances and improve image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If ink is ejected horizontally from nozzles at joint portions between vertically arranged inkjet heads, then printing coverage is improved, but pressure differences between adjacent nozzles cause varying drop distances and white streaks
Solution Approach 1:
The patent applies different ejection control strategies to different nozzle groups based on their vertical positions. Specifically, nozzles at joint portions (4th and 5th nozzles from each end) are controlled to eject fewer droplets or no droplets, while other nozzles maintain normal ejection. This local differentiation resolves the contradiction by preventing white streaks at critical joint portions while preserving printing coverage across the entire surface.
Solution Approach 2:
The patent changes the ejection parameters (number of droplets, ejection timing) for nozzles at joint portions compared to other nozzles. By adjusting these parameters locally at joint portions where pressure differences cause problems, the system maintains overall printing coverage while eliminating image quality defects at specific locations.
2Adaptability or versatility
If the head gap between inkjet head and print medium is increased, then printing flexibility is improved, but drop distance differences between upper and lower nozzles become more pronounced
Solution Approach 1:
The patent implements position-dependent control where nozzles at joint portions are treated differently from other nozzles. This local quality approach ensures that even when head gap is increased for printing flexibility, the problematic drop distance variations at joint portions are compensated by reducing ejection from those specific nozzles, maintaining overall image quality.
3Productivity
If multiple inkjet heads are arranged vertically to increase printing area, then productivity is improved, but pressure differences between adjacent nozzles at joint portions cause image quality deterioration
Solution Approach 1:
The patent maintains the vertically arranged multi-head configuration for increased productivity, but applies local quality control at joint portions. By reducing or stopping ejection from nozzles at joint portions (4th and 5th nozzles from each end), the system eliminates white streaks caused by pressure differences while preserving the high-productivity multi-head vertical arrangement for large area printing.
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
Suppresses white streaks and enhances image quality by equalizing drop distances and landing positions of ink droplets at joint portions between inkjet heads.
Implementation Method 1
pressure differences between nozzles due to the difference in hydraulic head differentials among nozzles within one inkjet head
Data Source
AI summary
A droplet ejection control apparatus includes a head unit in which a plurality of vertically arranged nozzle groups in which a plurality of nozzles for ejecting droplets onto a predetermined target of ejection are arranged in the vertical direction; and a control unit for controlling ejection of the droplets from the nozzles. The control unit controls ejection of the droplets for vertically adjacent nozzle groups such that an amount of ejection from at least one nozzle of a vertically upper nozzle group at a joint portion between nozzle groups is reduced, and an amount of ejection from at least one nozzle at the joint portion between the nozzle groups of a vertically lower nozzle group is increased.