| || Simulation of Droplet Formation, Ejection, Spread, and Preliminary Design of Nozzle for Direct Ceramic Inkjet Printing
Author : Reddy, A. Venumadhav;Rajesh, P. K.;Krishna Prasad, P. S. R. ;Ponnambalam, P. ;Prakasan, K.
Source : Defence Science Journal ; Vol:57(2) ; 2007 ; pp 287-297
Subject : 621.38 Electronics;681.2 Instrumentation
Keywords : Drop-on-demand;Direct ceramic inkjet printing;Piezoelectric actuation;DCUP Solid free forming;SFF;Inkjet printing
Abstract : Recent advances in drop-on-demand (DOD)-type inkjet printing techniques have increased research activities in the area of direct ceramic inkjet printing. In an attempt to develop a ceramic inkjet printer for the manufacture of ceramic components with their sizes in micro scale, the formation of ceramic ink droplet (ethyl alcohol loaded with different volume fractions of alumina particles) and its spread from a reservoir using piezoelectric actuation are simulated. The properties of the ceramic ink are taken from the data reported in literature. The simulations were performed with computational fluid dynamics software (CFD-ACE+), CFDRC. This study gives details of the interaction among different physical phenomena that contribute to the droplet formation and ejection process. The results from this study are being used for a preliminary design of nozzle and for the preparation of ceramic inks to achieve the desired droplet characteristics.
| || Rheological Behaviour of Ceramic Inks for Direct Ceramic Inkjet Printing
Author : Ponnambalam, P.;Ramakrishnan, N.;Rajesh, P.K.;Prakasan, K.
Source : Defence Science Journal ; Vol:56(2) ; 2006 ; pp 279-288
Subject : 620.1 Material Science and Technology
Keywords : Direct ceramic inkjet printing;Sediment packing density;Dispersant;Solid loading
Abstract : In this paper, studies were made on the preparation of ceramic inks with: (i) alumina powder in ethyl alcohol and (ii) zirconia powder in ethyl alcohol at different volume fractions of ceramic. Different amounts (0.75-3.00 vol %) of an organic dispersant (oleic acid) were added to ceramic ink containing 5 per cent of ceramic by volume in ethyl alcohol. The viscosities of the suspensions were determined with Brookefield viscometer (model: DV-E), which is suitable for measuring the viscosities of suspensions accurately. These inks were deposited on a substrate to see their spread. The sediment packing densities (fm) of the resulting suspensions were calculated using theoretical models which can be related to the density that can be achieved in the final product. The highest sediment packing density was arrived at low viscosity values of the ink and occurred when 1 per cent of dispersant by volume was used for 5 per cent alumina content. For 5 per cent zirconia content, 2 per cent of dispersant by volume gave a similar result. Experiments were also conducted to find the value of fm for different solid loadings (5-25 vol %) of ceramic with 1 per cent dispersant. It was observed that the sediment packing density and the apparent viscosities were increasing when solid loading concentrations were increased for both alumina and zirconia-based inks. The optimum value of fm and viscosity have been determined from this study. The results of this preliminary study will be useful for further investigations on the rheological behaviour of ceramic inks for direct ceramic inkjet printing.