微型噴墨三維模擬系統之開發及其實驗驗證

Development of a Three-Dimensional Simulation System for Micro-Inkjet and Its Experimental Verification

吳鉉忠(H. C. Wu) ； 黃文星(W. S. Hwang) ； 林惠娟(H. J. Lin)

《材料科學與工程》 36卷2期 (2004/06) Pp. 86-97

https://doi.org/10.6409/JMSE.200406.0086

摘要

本研究開發一可模擬壓電式噴墨系統在列印過程中之液滴生成、飛行與擊打到標的之三維電腦輔助分析系統。模擬以壓電式-收縮管型(squeeze tube mode)噴墨頭(printhead)為載具，模擬液滴生成、飛行與擊打到標的之完整過程，並以實驗觀測結果來驗證模擬系統的準確性。在模擬系統被驗證可靠之後，再據以進行數值實驗來評估表面張力與黏滯係數對液滴噴射行為的影響。
本研究之模擬系統在速度與壓力的求解上是使用SOLA (Solution Algorithm)數值技術，在界面重建及F值的傳遞問題上採用PLIC (Piecewise-Linear Interface Calculation )並耦合VOF (Volume of Fluid)法來計算，在表面張力的處理上是使用CSF (Continuum Surface Force) Model，壓電材料經受電壓影響而產生變形所造成的噴嘴壓力隨時間變化關係則是採用波傳導理論處理。實驗上所採用的噴墨頭為MicroFab公司所生產的壓電式收縮管型其型號為MJ-AB-01，使用CCD (Charge Couple Device) Camera擷取液滴影像。
模擬結果在液滴形態、斷裂時間、飛行距離與液滴體積四方面與實驗比對，具有良好的一致性。模擬結果並顯示當液體之表面張力較小，液滴串之斷裂時間較晚，液滴串之長度也較長，飛行速度較快，尾液滴較長，液滴呈現較不穩定的狀態，對噴墨列印品質而言，屬於較不理想之噴液。液體之黏滯性較大，對液滴串之斷裂時間的影響較不顯著，但液滴串長度則較短，飛行速度較慢，尾液滴較短，液滴較為穩定，對噴墨列印品質而言，屬於較佳之噴液。

關鍵字

壓電式噴墨列印、數學模擬、SOLA-VOF、CSF、PLIC

並列摘要

A three-dimensional computer-aided analysis system has been developed in this study to simulate the formation, ejection, and impact of liquid droplet in a squeeze-tube type piezoelectric inkjet printing device. The simulated results are compared with the corresponding experimental observations to verify the accuracy of the analysis system. The validated model is then employed to conduct numerical experimentation to evaluate the effects of surface tension and viscosity of the liquid on the ejection behaviors of the liquid droplet.
The computer simulation system is based on a SOLA (Solution Algorithm) scheme for the solution of velocity and pressure fields. It is coupled with VOF (Volume of Fluid) and PLIC (Piecewise-Linear Interface Construction) techniques for the transport of F values and construction of the interface. For the treatment of surface tension effects, a CSF (Continuum Surface Force) model is employed. The pressure at the nozzle inlet, which is related to the applied voltage, imposed on the simulation system is determined by the propagation theory of acoustic wave. For the experimental observations, a MJ-AB-01 piezoelectric printhead, which is a squeeze tube mode and manufactured by MicroFab Technologies, Inc., is employed. The images of the liquid droplets are captured by a CCD (Charge Couple Device) Camera.
The simulated results are rather consistent with the experimental observations in terms of droplet morphology, break-up time, flying distance, and droplet volume. The numerical experi- mentations show that for the liquid column as surface tension of the liquid decreases, the break-up time is longer, the length is longer, the flying velocity is faster, and its tail is also longer. The liquid droplet is relatively unstable, which is not desirable for the quality of the printing. As viscosity increases, the effect on break-up time is not obvious. However, the length becomes shorter, the flying velocity is slower, and its tail also becomes shorter. The liquid droplet is more stable and desirable for the printing quality.

並列關鍵字

piezoelectric inkjet printing, mathematical modeling, SOLA-VOF, CSF, PLICs