Continuous Liquid Ejection Drop Velocity Modulation
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Solution Overview
Problem
Existing continuous inkjet printing systems face challenges in achieving high resolution and print quality due to limitations in drop placement accuracy and tolerance of drop break-off length, requiring complex control systems and sensitive electrode configurations.
Innovation Solution
The use of mass charging and electrostatic deflection with a CMOS-MEMS printhead, employing image data-dependent control of drop formation and a charge electrode with a time-varying electrical potential, to create pairs of drops that can merge or be deflected independently, simplifying the design and improving drop placement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If individually addressable charge electrodes are used for each nozzle, then drop deflection control is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent merges the charging function for multiple nozzles into a single common charge electrode structure. Instead of having individual charge electrodes for each nozzle, one charge electrode serves multiple nozzles, reducing the number of electrodes required and simplifying the overall device complexity while maintaining the ability to control drop deflection for each nozzle through independent stimulation of the liquid jet
Solution Approach 2:
The patent applies preliminary charging to the liquid jet before drop break-off occurs. The common charge electrode charges the entire liquid jet stream upstream, and then independent stimulation at each nozzle causes selective break-off of charged drops. This preliminary charging action simplifies the electrode configuration by eliminating the need for individual charge electrodes at each nozzle location
2Manufacturing precision
If break off length is tightly controlled, then drop size uniformity is improved, but tolerance to manufacturing variations deteriorates
Solution Approach 1:
The patent employs dynamic control of the liquid jet through independent stimulation of each nozzle's liquid jet while using a common charge electrode. The system dynamically adjusts stimulation parameters for each nozzle to compensate for manufacturing variations, allowing the break-off length to be controlled adaptively rather than relying on fixed geometric constraints. This dynamic approach increases tolerance to nozzle array variations while maintaining drop size uniformity
Solution Approach 2:
The patent changes operational parameters (stimulation frequency, voltage, pulse width) to control drop formation and break-off. By adjusting these parameters independently for each nozzle, the system can compensate for manufacturing variations in nozzle geometry and positioning. The common charge electrode works in conjunction with variable stimulation parameters to maintain consistent drop characteristics despite variations in break-off length
3Manufacturing precision
If complex control systems are used to manage drop formation and deflection, then print quality is improved, but operational complexity increases
Solution Approach 1:
The common charge electrode performs multiple functions: it charges the liquid jet for all nozzles simultaneously, works with independent stimulation signals for each nozzle, and enables both drop formation control and deflection control through a single electrode structure. This multi-functionality reduces operational complexity by eliminating the need to separately control individual charge electrodes for each nozzle while maintaining high print quality
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 enhances print quality and resolution while reducing drop volume variation and operational complexity, allowing for larger tolerances in nozzle arrays and improved drop placement accuracy.
Implementation Method 1
the liquid jet stream is perturbed in some fashion causing it to break up into uniformly sized drops at a nominally constant distance, the break-off length, from the nozzle
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
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AI summary
A continuous liquid ejection system includes a liquid chamber in fluidic communication with a nozzle. The liquid chamber contains liquid under pressure sufficient to eject a liquid jet through the nozzle. A drop formation device is associated with the liquid jet and is actuatable to produce a modulation in the liquid jet that cause portions of the liquid jet to break off into a series of drop pairs traveling along a path. Each drop pair is separated in time on average by a drop pair period. Each drop pair includes a first drop and a second drop. A charging device includes a charge electrode associated with the liquid jet and a source of varying electrical potential between the charge electrode and the liquid jet. The source of varying electrical potential provides a waveform that includes a period that is equal to the drop pair period. The waveform also includes a first distinct voltage state and a second distinct voltage state. The charging device is synchronized with the drop formation device to produce a first charge state on the first drop and to produce a second charge state on the second drop. A drop velocity modulation device varies a relative velocity of a first drop and a second drop of a selected drop pair to control whether the first drop and the second drop of the selected drop pair combine with each other to form a combined drop. The combined drop has a third charge state. A deflection device causes the first drop having the first charge state to travel along a first path, causes the second drop having the second charge state to travel along a second path, and causes the combined drop having the third charge state to travel along a third path.