CUED Publications database

Towards satellite free drop-on-demand printing of complex fluids

Morrison, NF and Harlen, OG and Hoath, SD (2014) Towards satellite free drop-on-demand printing of complex fluids. In: UNSPECIFIED pp. 162-165..

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© 2014 Society for Imaging Science and Technology. We investigate the influence of fluid properties on jet breakup in the context of drop-on-demand inkjet printing. In drop-on-demand printing, each drop remains temporarily connected to the printhead by a ligament which thins while the drop is in flight. Upon pinch-off the severed ligament may recoil into the leading drop, or it may fragment into 'satellite drops' which reduce printing resolution. A key goal of inkjet research is to prevent or impede the creation of satellite drops while maintaining a high drop speed. Complex fluids often exhibit enhanced resistance to fragmentation in jetting flow s compared to Newtonian fluids of similar viscosity [1]. Indeed, some complex fluids have been found in experiments to produce satellite-free jets even at high drop speeds [2] . In this work we exploit rheological considerations with the aim of eliminating satellite drops when printing at prescribed drop speeds, without any alterations to the driving waveform other than a simple amplification. In explicit terms, we attempt to design the rheology of the fluid in such a way as to calibrate its effective viscosity during the key stages of a drop-on-demand flow cycle. Using a purely shear-thinning fluid model, we outline the key fluid parameters and dimensionless groups and we use a Lagrangian finite-element numerical method [3] to simulate a drop-on-demand printing flow under realistic industrial inkjet conditions, exploring the parameter space of critical fluid properties for a variety of drop speeds. We show that a shear-thinning fluid model with calibrated viscosity plateaus is able to eliminate satellites without compromising on drop speed and without adjusting the driving waveform. The present study complements previous work in which we have presented results of drop-on-demand simulations for a vis-coelastic fluid model with constant shear-viscosity [4] , a generalized Newtonian fluid model (shear-thinning) [5], and the Giesekus fluid model which is both viscoelastic and shear-thinning [6] . In each case we demonstrated the capacity of non-Newtonian fluid properties to reduce the number and net volume of satellite drops. In these works, the elimination or reduction of satellites was considered only as a desirable potential outcome; by contrast, in the current work the elimination of satellites is imposed as a requirement.

Item Type: Conference or Workshop Item (UNSPECIFIED)
Divisions: Div E > Production Processes
Depositing User: Cron Job
Date Deposited: 17 Jul 2017 19:45
Last Modified: 03 Aug 2017 03:14