Inkjet Fluid Dynamics and Fundamentals - Part 1: Acoustics of Piezo Print Heads: The Physics of Drop Ejection
Instructor: J. Frits Dijksman, University of Twente
Duration: 2:00 plus 15 minute break. After the class, adjourn to Zoom to join the instructor and other students in a discussion of the class.
New York: Monday 12 October 10:00 - 12:15
London: Monday 12 October 15:00 - 17:15
Tokyo: Monday 12 October 23:00 - Tuesday 13 October 01:15
This course enables an attendee to:
- Appreciate the influence of pulse shape on pump performance.
- Discern the basics of formulation of ink in terms of viscosity, density, wave speed of sound, and surface tension.
- Understand the importance of the different design options for throttle, pump chamber, and nozzle.
- Get a feeling the influence of applying under-pressure to prevent the print head from leaking during idling.
- Understand the effect of enclosed air bubbles.
- Obtain a basic idea on piezo performance and electrical time constant.
Intended Audience: Scientists and engineers interested in designing and tuning piezo inkjet print heads.
Piezo driven droplet-on-demand inkjet print heads consist of a large number of parallel integrated piezo actuated valve less pumps. Each pump is a series connection of a throttle (the connection to the main supply channel), a pump chamber, and a nozzle (the connection to ambient). Such pumps are acoustic cavities filled with ink and upon actuation pressure waves are generated in the ink. At the nozzle these pressure waves are transferred into a time dependent fluid velocity and ultimately in one droplet or more droplets (satellites). The action of such a pump depends on the pulse shape (height, rise time, dwell time and fall time, or more complicated shapes), the driving frequency, the layout of the pump, in particular, the dimensions of throttle, pump chamber, and nozzle and ink properties like viscosity, density, the wave speed of sound and surface tension.
J. Frits Dijksman obtained his masters (1973) and PhD (1978) at the Technical University of Delft in The Netherlands. He worked with Philips Research Laboratories in Eindhoven, The Netherlands, for 32.5 years, mainly on inkjet printing, rheology of polymers, and medical devices. After his retirement he became part time professor in fluid dynamics at the University of Twente, The Netherlands. He is the author of a book Design of Piezo Inkjet Print Heads (Wiley-VCH 2018). He is now emeritus professor.
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