다중 노즐 잉크젯 헤드의 상호 간섭 측정 및 평가

권계시(Kye-Si Kwon),김진원(Jin-Won Kim) Korean Society for Precision Engineering 2011 한국정밀공학회지 Vol.28 No.1

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.

Optimization of pulsed voltage waveform for electrohydrodynamic jetting on-demand

양정근,조백현,정재원 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.8

For electrohydrodynamic jetting-on-demand, the conventional positive voltage pulse superposed by a dc bias voltage have been widely used. Once this voltage pulse was induced, the meniscus at the nozzle tip oscillated and its volume changed owing to the fluid supplied through the nozzle as well. To increase the maximum frequency for consistent jetting, it is desirable to minimize these phenomena. When the oscillation amplitude was sufficiently small to assume the occurrence of linear behavior and no jetting, the above phenomena could be well explained by using a harmonic oscillator model and a one-dimensional flow model. Based on this physical understanding, the root-polar voltage waveform was proposed and could significantly decrease the change in meniscus height; thus it was possible to increase the maximum frequency for consistent jetting. In addition, the residual oscillation could be also suppressed using an extra voltage pulse waveform. Furthermore, the root-polar voltage waveforms with a minus voltage pulse as well as a positive one could be demonstrated; thus it was shown that the root-polar voltage waveform could be implemented into ac-pulse modulated EHD jetting as well.

금속첨가제를 포함하는 3DP용 무기바인더가 적용된 주형의 물리적 특성

편성은,이만식,박대원,백재호 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1

Binder jetting은 분말 소재 상에 액상 결합제를 선택적으로 분사하여 3차원 구조물을 제조하는 기술로 정의된다. 본 프린팅 방식의 바인더의 경우 환경성, 안정성 그리고 작업성의 측면에서 기타 오염물질을 배출하지 않는 친환경 무기바인더의 개발에 대한 요구가 증대되고 있다. 하지만, 물유리 기반 무기바인더는 대기 중에 방치되는 시간이 길어짐에 따라 특유의 흡습성으로 인해 주형 제작 시의 물성 저하에 큰 영향을 미친다. 본 연구에서는 취약한 내수성을 개선하기 위해서 금속첨가제를 도입하여 3D 프린팅에 적합한 무기바인더를 제조하였다. 특히, 선행연구를 통해 토출 조건이 최적화된 무기바인더 함량으로 선정하여 금속첨가제에 따른 영향을 검토하였다. 그 결과, Na 첨가에 따라 일반강도가 소폭 증가하고 Li 첨가에 따라 취약했던 내수강도가 개선되는 결과를 확인할 수 있었다.

Influence of the jetting fluid on the internal flow in a centrifugal pump with jetting device

BaoLing Cui,Qianqian Yang,Kaicheng Zhu 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.3

Jetting the high pressure fluid from the outlet to the inlet is one of the methods to improve the cavitation characteristics. The influences of different jetting flow rates on the external characteristics and internal flow were investigated in the centrifugal pump with jetting device. The experiments were carried out to verify the performance calculated from the numerical simulation. The internal flow was analyzed under the design condition with 0-10 % jetting flow rate. The results indicate the jetting fluid makes the distributions of velocity more uneven in the jetting device. As the jetting flow increases, the entropy generation rate in the jetting device and inlet pipeline shows an incrementally increasing trend, indicating that the hydraulic loss is gradually increasing. At the same time, the pressure at the inlet of the impeller increases, and the turbulent kinetic energy decreases at the centrifugal pump impeller. This research is of great significance to effectively improve operational stability of the centrifugal pump.

CCD 카메라를 사용한 전기수력학적 잉크젯 토출 현상 가시화

권계시(Kye-Si Kwon),이대용(Dae-Yong Lee) Korean Society for Precision Engineering 2012 한국정밀공학회지 Vol.29 No.3

The method for spraying of liquids through an electrical field has become a printing method since it can make very small droplet. For electro-hydrodynamic jet printing to become a reliable jetting tool, the jetting performance should be characterized with respect to various jetting conditions. To optimize jetting conditions, the jetting behavior should be measured. In this study, we present a visualization techniques to measure jetting behavior from electro-hydrodynamic (EHD) inkjet head. Unlike most previous method, we use the CCD camera to measure the jetting behavior. For this purpose, LED light is synchronized with jetting signal and sequential image was obtained by adjusting the delay time of the LED light. Finally, merits and demerits of using CCD camera were discussed to measure jetting image from EHD inkjet head.

Jetting Properties of Inorganic Binders with Stable Droplet Formation in 3D Printing

편성은,백재호,박대원,이만식 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0

Binder jetting (BJ) is one of 3D printing technologies to manufacture 3D geometries, in which a liquid binding agent is ejected to desired position of substrates. For this process, binder properties and jetting condition affect the formability of the geometries. In general, a binder with low viscosity is accompanied by many satellite droplets after ejection and degrades printing quality. For high viscosity, nozzle clogging occurs due to viscous dissipation. In this study, to develop inorganic binders with appropriate jetting properties, we prepared inorganic binders by adding additives such as humectants to water glass. Physical properties were determined by viscosity, surface tension, and density. In order to investigate jetting properties, we analyzed theoretical-experimental behaviors of ejected droplets by Ohnesorge number and jetting test, respectively. Therefore, we confirmed jettable ranges of the prepared binders with stable droplet formation depending on jetting condition.

Pyrolytic Jetting of Highly Porous Laser-Induced Graphene Fiber for Cost-Effective Supercapacitor

Dongwoo Kim,Hyunkoo Lee,Eunseung Hwang,Sukjoon Hong,Habeom Lee 한국정밀공학회 2024 International Journal of Precision Engineering and Vol.11 No.2

The recently reported laser pyrolytic jetting process enables facile generation of highly porous, free-standing graphene fiber from polyimide film upon the scanning of tightly focused continuous-wave laser. As a follow-up study, we claim that the corresponding laser pyrolytic jetting process is favorable for the fabrication of relevant energy device applications compared to the conventional LIG process in both energy-saving and material-saving perspectives. Moreover, the volume of the pyrolysis product is substantially increased in the case of pyrolytic jetting compared to conventional LIG, resulting in an extended surface area for storing more electric charges. At the same time, material characterization by Raman measurement validates that the exfoliated product from pyrolytic jetting is analogous to the conventional LIG and therefore suitable for supercapacitor application. As a result, supercapacitor created by the pyrolytic jetting allows substantial enhancement in the capacitance compared to the conventional LIG for both with and without manganese oxide layer coating, proposing the potential of pyrolytic jetting for the efficient fabrication of carbon-based energy devices.

Experimental and numerical study of the performance and cavitation flow of centrifugal pump with jetting device

BaoLing Cui,Kaicheng Zhu,Yuliang Zhang,Peifeng Lin 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.10

Cavitation is a problem that must be considered when designing and operating a pump. This study proposes an active method using a jetting device to improve its cavitation performance. The influence of jetting flow rate on the external characteristics and cavitation performance of a centrifugal pump is analyzed through numerical simulation and experiment. Results show that the jetting fluid can improve the cavitation performance of a pump and the effect is most evident in the 6 % jetting flow rate. The distribution of entropy generation at the inlet pipe before the impeller shows that jetting flow can increase hydraulic loss in the pipe, thereby diminishing the performance of the centrifugal pump. An analysis of the transient cavitation flow in the centrifugal impeller under 6 % jetting flow rate reveals that the generation, development, and rupture of bubbles deteriorate the flow structure in the passage, thereby resulting in unstable flows and forces.

Evaluation of jet performance in drop-on-demand (DOD) inkjet printing

Byoung Wook Jo,Ayoung Lee,Seung Jong Lee,이승종 한국화학공학회 2009 Korean Journal of Chemical Engineering Vol.26 No.2

Inkjet printing has been widely used in many applications and has been studied for many years. However, there are not many systematic researches on the mechanism of jet formation, nor is there any reliable platform that enables us to evaluate jet performance. In this study, an approach to practically evaluate the jet stability of the dropon-demand (DOD) inkjet printing has been proposed, based on which the transient behavior of the DOD drop formation has been studied experimentally for Newtonian liquids with a range of different viscosities (1.0-11 cp) but of a comparable surface tension. For more viscous liquids, the rate of the jet retraction after a pinch-off from the nozzle was found to increase as the thread motion became more sharp and conical as a result of the shape effect. The break-up time of the jet also increased because the rate of capillary wave propagation was lower for more viscous liquids. The jet stability graph, which can be drawn in terms of jet retraction and break-up time, was employed to characterize the jetting stability, and the degree of satellite drop generation was quantitatively evaluated by two critical jet speeds. The effect of an electric pulse imposed on a piezoelectric plate inside the printhead was also studied. The single-peak electric pulse was used in this experiment for simple analysis, and the jet speed variation was measured under different operating conditions. Both the optimal dwell time and the maximum stable jetting frequency were affected by viscosity and they were explained in terms of the propagation theory.

Effect of water jetting parameters on the penetration behavior of jack-up spudcan in surficial sand condition

Han, Dong-Seop,Kim, Seung-Jun,Kim, Moo-Hyun Techno-Press 2015 Ocean systems engineering Vol.5 No.1

The water jetting system for a jack-up spudcan requires the suitable design considering the platform/spudcan particulars, environments, and soil conditions, either the surficial clay or surficial sand. The usage of water jetting depends critically on soil conditions. The water jetting is usually used for the smooth and fast extraction of the spudcan in the surficial clay condition. It is also required for inserting spudcan up to the required depth in the surficial sand condition, which is investigated in this paper. Especially, it should be very careful to use the water jetting during an installation of spudcan in the surficial sand condition, because there is a risk of overturning accident related to the punch-through. Therefore, in this study, the effect of water jetting flow rate and time on the change of soil properties and penetration resistance is analyzed to better understand their interactions and correlations when inserting the spudcan with water jetting in surficial sand condition. For the investigation, a wind turbine installation jack-up rig (WTIJ) is selected as the target platform and the multi layered soil (surficial sand overlaying clays) is considered as the soil condition. The environmental loading and soil-structure interaction (SSI) analysis are performed by using CHARM3D and ANSYS. This kind of investigation and simulation is needed to decide the proper water jetting flow rate and time of spudcan for the given design condition.