Drop Formation Waveforms for Crosstalk Reduction
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Solution Overview
Problem
In continuous inkjet printing systems, the formation of large drops is often incomplete before reaching the deflection air flow, leading to unintended merging with small drops and neighboring jets, causing disturbances and affecting print quality due to acoustic stimulation crosstalk and uneven drop spacing.
Innovation Solution
A method involving specific drop waveforms with a small drop waveform period approximately equal to the Rayleigh frequency and a large drop waveform with a second pulse occurring within a specific time frame of a subsequent small or large drop waveform, reducing drop formation length and minimizing disturbance to neighboring jets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a large drop waveform with period Nx is used to form large-volume drops, then the drop volume is increased, but the drop formation length increases causing incomplete coalescence before deflection
Solution Approach 1:
The large drop waveform is segmented into multiple pulses within the period Nx. The first pulse initiates drop formation and the second pulse completes coalescence, dividing the drop formation process into distinct stages that occur within a shortened overall formation length
Solution Approach 2:
The waveform uses periodic pulsing with period Nx where N is an integer. This periodic action creates controlled disturbances at regular intervals, enabling systematic manipulation of drop formation timing and location to achieve complete coalescence within a reduced formation length
2Length of moving object
If the drop formation length is reduced to enable earlier size separation, then the print head size is reduced, but the large drops may not fully coalesce before deflection
Solution Approach 1:
The first pulse of the large drop waveform initiates drop formation in advance, creating an initial disturbance that begins the coalescence process early. This preliminary action allows the drop formation to start before the drop reaches the deflection region, ensuring complete coalescence within the reduced formation length
Solution Approach 2:
The second pulse in the large drop waveform acts as a feedback mechanism that monitors and completes the coalescence process. By applying a second pulse within the period Nx, the system ensures that any incomplete coalescence is corrected, guaranteeing complete drop formation before deflection
3Manufacturing precision
If small-volume drops are produced with period x at Rayleigh frequency, then the drop spacing is controlled, but uneven spacing and unintended merging with large drops occurs
Solution Approach 1:
The system changes the waveform parameters (period, pulse width, amplitude) depending on the desired drop volume. Small drops use period x at Rayleigh frequency while large drops use period Nx with multiple pulses. This parameter adjustment controls drop spacing and minimizes acoustic stimulation crosstalk between neighboring jets
Solution Approach 2:
Each jet in the nozzle array is assigned a specific waveform pattern tailored to its function. Jets producing small drops receive one waveform while jets producing large drops receive a different waveform. This local customization ensures optimal drop spacing and minimizes harmful acoustic interactions between adjacent jets
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 ensures complete coalescence of large drops before deflection, reduces drop formation length, and minimizes disturbances to neighboring jets, enhancing print quality and reducing the risk of incomplete or merged drops.
Implementation Method 1
periodic heat pulses drive capillary break-up of jets formed at each nozzle to produce an array of drops
Implementation Method 2
the jet responds most sensitively to disturbances at a characteristic frequency fR known as the Rayleigh frequency
Implementation Method 3
A gas flow directed across the stream of ink drops interacts with the stream of ink drops. This interaction deflects smaller drops more than larger drops
Data Source
AI summary
A liquid stream is caused to jet from a nozzle. A small or large drop waveform applied to a drop forming mechanism causes the liquid stream to break up into a small or large volume drop, respectively. The small drop waveform includes a pulse having a width wS, and a period x, where x≈1/fR, where fR is the Rayleigh frequency of the liquid. The large drop waveform includes a period Nx, with the large volume drop being N times the small volume drop. The large drop waveform includes a first pulse having a pulse width wL1, where wL1≧wS, and a second pulse occurring within a period of (fR/fC)x of an initial pulse of a subsequent small or large drop waveform, where fC is the cut off frequency of the liquid. The second pulse includes a pulse width wL2, where wL2<wS.