(159n) Dynamics of Fluids and Inkjet Printers

There are two models of producing inkjet printers that is continuous mode and drop on demand. In continuous mode ink-jet printing systems, droplets are produced that are approximately twice the orifice diameter of the droplet generator. Droplet generation rates for commercially available continuous mode ink-jet systems are usually in the 80-100 kHz range, but systems with operating frequencies up to 1MHz are in use. Droplet sizes can be as small as 20 μm in a continuous system, but 150 μm is typical. Inkjet printer, a dot-matrix printing technology, drop on demand (DOD) and continuous ink-jet printing (CIJ). DOD printer requires a jet of liquid exits as a drop under surface tension forces to be forced CIJ printing involves breaking a continuous jet into droplets. Short time thinning and break-up behavior are of particular relevance to ink jet processing where base viscosities are normally below 20 m Pas, and timescales are very short relaxation times of less than 10 ms. In DOD, a volumetric change in the fluid is induced by the application of a voltage pulse to a piezoelectric material that is coupled, directly or indirectly, to the fluid. This volumetric change causes pressure and velocity transients to occur in the fluid and these are directed so as to produce a drop that issues from an orifice. Since the voltage is applied only when a drop is desired, these types of systems are referred to as drop-on-demand, or ‘demand mode’.