• Journal of the Korean Society for Precision Engineering
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• v.28 no.1
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• pp.73-79
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• 2011

Inkjet printhead may have a lot of nozzles to increase productivity as a manufacturing tool. So, the uniformity of jetting performance among a lot of nozzles has been one of the key issues in inkjet technology In this study, we investigated the cross-talk effect which should be reduced for uniform jetting performance among a lot of nozzles. Due to the cross-talk, the jetting performance of a nozzle can be affected when neighboring nozzles are firing. For experimental study, we used commercial inkjet head SE-128 from Dimatix. To understand the cross-talk effect of SE-128 head, we measured the change in jetting speed of a nozzle when neighboring nozzles are jetting. The measured jetting speed was compared to the case of one nozzle jetting. Also, we used laser vibrometer to measure change in pressure wave due to cross-talk. As a result of the cross-talk, the jetting speed can become faster or sometimes slower depending on firing nozzle location. If the all nozzle are jetting, the jetting speed of a nozzle became slower because the pressure wave for jetting is reduced.

• Journal of the Semiconductor & Display Technology
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• v.4 no.2 s.11
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• pp.21-24
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• 2005

Ink-jetting characteristics of pulse width and pulse amplitude for a piezoelectric ink jet printer driver have been mapped with various polymer EL ink. In this study, the jetting characteristics have been classified into 4 regime; no Jetting, unstable jetting, stable jetting, and spraying, and the importance of fluid viscosity on the scope of the stable jetting regime has been emphasized. The relation between jetting speed and the width and amplitude of driving signal has also been investigated and the effect of the speed on the jetting characteristics has been discussed.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.9
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• pp.143-147
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• 2009

Inkjet printing makes use of ink droplets to form required patterns on a substrate. In order for the inkjet technology to produce reliable patterning tools, the jetting performance needs be controlled precisely. For controlling ink jetting performance, input waveform should be properly designed. In the past, the research was focused on designing dwell time of the input waveform for controlling jetting speed. However, the jetting performance is also closely related to rising and falling time. In this study, the effect of the rising and falling time on droplet speed will be investigated by measuring the droplet speed. In this study, the power OP amp (PA98A) was used in order to drive piezo inkjet head by amplifying the waveform generated from arbitrary function generator. The experimental results show that change of rising and falling time in the waveform not only affect the droplet speed but also optimal dwell time.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.4
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• pp.449-454
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• 2012

The method for spraying of liquid through an electrical filed has become a printing method since it can make very small droplet. To increase the reliability using the electro-hydrodynamic (EHD) jet printing, the jetting status needs to be monitored. Vision measurement techniques using high speed camera has been used to visualize the jet images. However, it requires image processing of a lot of images after image acquisitions. So, it is difficult to understand jet behavior such as jetting frequency, jet repeatability etc. In this work, a low cost electrical current measurement method was developed to measure electrical current from EHD jet printing. To verify the jetting monitoring capability of developed circuit, images from high speed camera were processed for comparison purpose.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1913-1916
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• 2008

Electrohydrodynamic (EHD) printing has gained significant interest after a direct writing with a resolution of a few tens nanometer was demonstrated using EHD. Basically, EHD use the electric field to generate droplet which is much smaller than nozzle diameter, so that high resolution printing is possible and the clogging problem can be alleviated as well. However, to adapt this technology to the real application, the fundamental studies are necessary to stabilize EHD jetting, to maximize jetting frequency, and to optimize the design of multi EHD nozzle, etc. In this study, by imaging EHD jetting using high speed camera and measuring the current, the effect of electric field intensity and back pressure on jetting frequency and jetting diameter were studied.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.4
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• pp.432-438
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• 2008

This paper presents a new jetting dispenser driven by a piezoelectric actuator at high operating frequency to provide very small dispensing dot size of adhesive in modern semiconductor packaging processes. After describing the mechanism and operational principle of the dispenser, a mathematical model of the structured system is derived by considering behavior of each component such as piezostack and dispensing needle. In the fluid modeling, a lumped parameter method is applied to model the adhesive whose rheological property is expressed by Bingham model. The governing equations are then derived by integrating the structural model with the fluid model. Based on the proposed model, dispensing performances such as dispensing amount are investigated with respect to various input trajectories.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.10
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• pp.1521-1527
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• 2010

Since inkjet printing is being employed in production lines of electronics and display industries, the tack time for inspection of jetting failure has become very important because the throughput of the inkjet printing system can be extended to the maximum limit by adopting a shorter jetting inspection time. The most popular method for inspecting jetting failure involves the use of a linear stage, a high magnification lens, and a charge coupled devicecamera. However, this conventional approach requires approximately 60 s to complete the jetting inspection and might not be suitable for a high-speed reciprocating jetting inspection in endurance tests due to the unwanted mechanical vibration. In this study, a novel concept of an inkjet monitoring module is introduced, which has an overall inspection time of 18 s. For the shorter tack time of jetting inspection, the parameters affecting the tack time are discussed in this paper.

• Transactions of Materials Processing
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• v.12 no.1
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• pp.3-10
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• 2003

The formation of surface defects associated with Jotting in injection molding is related to the geometries of cavity and fate, operational conditions and the rheological properties of polymer. In this study we have examined jetting phenomena in injection molding process for the throe kinds of PCs which have different molecular weights and structures, PBT and PC/ABS alloy with several injection speeds. We have used various cavity shapes those are tensile, flexural and impact test specimens with various gates and cavity thicknesses. Through this study we have observed that the jetting is related to the dic swell of material. This means that the jotting is strongly affected by the elastic flow property rather than the viscous flow property in viscoelastic characteristics of molten polymer. Different resins have different elastic properties, and elastic flow behavior depends on the shear rate of flow, i.e. injection speed. Large die swell would eliminate jetting however, the retardation of die swell would stimulate jetting. In the point of mole design, reducing the thickness ratio of cavity to gate can reduce or eliminate jetting regardless of amount of elasticity of polymer melt.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.562-565
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• 2008

Measuring system for piezo inkjet droplet and ink jetting status was developed. In order to measure the jetting performance, two different approaches have been used. One is to use the self-sensing capability of the piezo actuator in the printhead. The other is to use the droplet image from a CCD camera. The software as well as hardware using two approaches was developed. The self-sensing signal as well as meniscus motion was shown to be useful in monitoring jetting conditions. Furthermore, ink properties such as viscosity and speed of sound, which is related to jetting performance, can be understood.

• International Journal of Fluid Machinery and Systems
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• v.7 no.3
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• pp.125-129
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• 2014

The paint removal and recoating are the very important process in airplane maintenance. The traditional technology is to use the chemical way corroding the paint with paint remover. For changing the defects, corrosion & pollution & manual working, of the traditional technology, the physical process which removes the paint of airplane with 250MPa/250kW ultra-high pressure rotary water jetting though the surface cleaner installed on the six axes robot is studied. The paint layer of airplane is very thin and close. The contradiction of water jetting paint removal is to remove the paint layer wholly and not damage the surface of airplane. In order to solve the contradiction, the best working condition must be reached through tests. The paint removal efficiency with ultra-high pressure and move speed of not damaged to the surface. The move speed of this test is about 2m/min, and the paint removal efficiency is about $30{\sim}40m^2/h$, and the paint removal active area is 85-90%. No-repeat and no-omit are the base requests of the robot program. The physical paint removal technology will be applied in airplane maintenance, and will face the safety detection of application permission.