Drop-on-demand Jetting Waveform Control for Meniscus Stabilization
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Solution Overview
Problem
Ink jet printers face challenges in maintaining stable and reproducible jetting behavior at high drop-on-demand frequencies due to the influence of meniscus conditions, which depend on the history of the jetting device, leading to variations in droplet volume and speed, and compromising print quality when drop frequencies are not constant.
Innovation Solution
Energizing the actuator with a waveform that extends beyond the drop-on-demand period and ignoring the drop signal in the subsequent period to optimize pressure wave shaping, ensuring stable jetting conditions, and using pre-fire and jetting pulses with fixed time delays to maintain a well-defined meniscus state, even when no droplet is expelled in the current period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the actuator is energized with a pre-fire pulse in the preceding DOD period to compensate for residual pressure wave effects, then the jetting behavior stability is improved, but the DOD frequency is limited due to the lower limit on DOD period length
Solution Approach 1:
The pre-fire pulse is applied in advance in the preceding DOD period to create a pressure wave that compensates for the residual pressure wave effect. This preliminary action prepares the meniscus in advance to be in a well-defined state before the actual jetting pulse, ensuring stable jetting behavior while allowing shorter DOD periods and higher frequencies.
2Reliability
If the pre-fire pulse is formed in the preceding DOD period, then the jetting behavior is stabilized, but the print quality is compromised when DOD frequency is not constant due to varying time delays
Solution Approach 1:
The time delay between the pre-fire pulse and the jetting pulse is made dynamic rather than fixed. The control unit adjusts the time delay adaptively based on whether the DOD frequency is constant or variable. When DOD frequency is constant, a fixed time delay can be used; when it is variable, the time delay is adjusted dynamically to maintain optimal jetting conditions and print quality.
3Productivity
If the DOD period length is reduced to increase DOD frequency, then the productivity is improved, but the jetting behavior becomes unstable due to insufficient time for pressure wave propagation and meniscus stabilization
Solution Approach 1:
The pre-fire pulse is applied in advance during the preceding DOD period to create and stabilize the pressure wave and meniscus configuration before the actual jetting pulse. This preliminary preparation ensures that even when the DOD period is shortened to increase frequency, there is sufficient time within the extended waveform for proper pressure wave propagation and meniscus stabilization, maintaining jetting stability at high frequencies.
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 stabilizes jetting behavior and improves print quality by maintaining consistent droplet volume and speed, even at high frequencies, by ensuring the meniscus is in a well-defined state, reducing the impact of varying time delays and residual pressure fluctuations.
Implementation Method 1
the actuator is energized so as to excite a pressure wave in the liquid in the pressure chamber. The pressure wave propagates to the nozzle, where an ink droplet is jetted out onto the recording medium.
Data Source
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AI summary
A method of operating a drop-on demand (DOD) jetting device having a nozzle, a pressure chamber filled with a liquid and connected to the nozzle and an actuator energized by a drive signal, wherein a periodic DOD signal determines whether or not a droplet is jetted out from the nozzle in a given DOD period (n-1), and the drive signal has a waveform configured to cause the actuator to excite a pressure wave in the liquid, the method being characterized by comprising the steps of a) energizing the actuator with a waveform (54) that has a fixed pattern and extends over a time interval that is longer than the given DOD period (n-1); and b) ignoring the DOD signal in at least the first DOD period (n) that follows after the period (n-1) for which the step a) has been performed.