Drop Velocity Modulation in Continuous Inkjet Printheads
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Solution Overview
Problem
Existing continuous inkjet printing systems face challenges in achieving high resolution and print quality due to the need for precise drop placement and the complexity of controlling drop break-off lengths and charge electrode alignment, which are sensitive to variations in nozzle spacing and ink properties.
Innovation Solution
A CMOS-MEMS printhead system uses mass charging and electrostatic deflection with synchronized drop formation and charge electrode waveforms to create drop pairs, allowing for controlled merging of drops and improved drop placement accuracy, while reducing the complexity of charge electrode structures and increasing nozzle spacing tolerance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If individual charging electrodes are used for each nozzle in continuous inkjet printing, then drop placement precision is improved, but device complexity and manufacturing difficulty increase significantly
Solution Approach 1:
The patent merges the charging function for multiple nozzles into a single common charging electrode. This electrode extends across the entire array of nozzles and charges all drops simultaneously as they pass by, eliminating the need for individual charging electrodes at each nozzle while maintaining precise drop placement through subsequent deflection control
2Manufacturing precision
If break-off length is precisely controlled for high resolution printing, then manufacturing precision is improved, but the system becomes more sensitive to variations in nozzle spacing and ink properties
Solution Approach 1:
The patent employs dynamic control of drop velocity through individually addressable deflection electrodes rather than relying on precise static control of break-off length. By deflecting charged drops during their flight path, the system can dynamically adjust drop placement to compensate for variations in nozzle spacing, ink properties, and break-off timing, thereby improving reliability while maintaining high resolution
3Productivity
If closely spaced nozzles are used to increase resolution, then productivity is improved, but the tolerance for nozzle spacing variations decreases
Solution Approach 1:
The system uses feedback through individually controllable deflection electrodes for each nozzle. These electrodes receive control signals that compensate for variations in drop trajectory caused by nozzle spacing tolerances, ensuring that drops from closely spaced nozzles are accurately positioned on the recording medium despite manufacturing variations
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 enables high-resolution, high-quality prints with minimized drop volume variation and improved robustness against break-off time variations, reducing the likelihood of liquid splatter and simplifying control signals for nozzle arrays.
Implementation Method 1
The stream of ink is perturbed in a manner such that the liquid jet breaks up into drops of ink in a predictable manner
Implementation Method 2
A charging electrode structure is positioned at the nominally constant break-off point so as to induce a data-dependent amount of electrical charge on the drop at the moment of break-off
Implementation Method 3
The charged drops are then directed through a fixed electrostatic field region causing each droplet to deflect proportionately to its charge
Data Source
AI summary
A continuous ejection system includes a chamber containing liquid under pressure sufficient to eject a liquid jet through a nozzle. A drop formation device modulates the jet causing portions to break into drop pairs including first and second drops separated in time on average by a drop pair period. A charging device includes a varying electrical potential source providing a waveform including first and second distinct voltage states and a period equal to the drop pair period. The charging device produces first and second charge states on first and second drops of the drop pair, respectively. A drop velocity modulation device varies a relative velocity of first and second drops of selected drop pairs causing first and second drops of selected drop pairs to form combined drops having a third charge state. A deflection device causes the first, second, and combined drops to travel along different paths.