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Impedance Matched DOD Printhead Channel

IP.com Disclosure Number: IPCOM000062545D
Original Publication Date: 1986-Dec-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Ream, GL: AUTHOR

Abstract

To achieve good print quality at high frequencies of operation, e.g., 10 KHz, a drop-on-demand (DOD) printhead must be designed such that the "reflection history" within the printhead is minimized. Internal reflections produce resonances within the drop generator channel -- which, in turn, limit the maximum frequency of operation due to spurious drop generation. To minimize internal reflections, it is necessary to avoid mismatches in acoustical impedance within the channel or at least spread out changes in impedance. To avoid any mismatch in acoustical impedance within the channel, each material within the channel must be evaluated to either theoretically or experimentally determine the acoustical wave velocity when that material is used as a waveguide.

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Impedance Matched DOD Printhead Channel

To achieve good print quality at high frequencies of operation, e.g., 10 KHz, a drop-on-demand (DOD) printhead must be designed such that the "reflection history" within the printhead is minimized.

Internal reflections produce resonances within the drop generator channel -- which, in turn, limit the maximum frequency of operation due to spurious drop generation. To minimize internal reflections, it is necessary to avoid mismatches in acoustical impedance within the channel or at least spread out changes in impedance. To avoid any mismatch in acoustical impedance within the channel, each material within the channel must be evaluated to either theoretically or experimentally determine the acoustical wave velocity when that material is used as a waveguide. For instance, a steel wall results in a high wave velocity (nominally 1430 m/s with water); a piezoelectric (PZT) crystal with a 10-mil wall thickness results in a medium velocity (nominally 1360 m/s with water); and a wall made with plastic such as polyphenylene oxide results in a low velocity (nominally 825 m/s with water). The acoustical impedance of each segment of the waveguide channel is given by the expression: (1)

Z = rho x ci/Si whererho = Fluid density, ci = Wave velocity in waveguide segment i,

Si = Cross-sectional area of waveguide segment i. In accordance with this expression, the cross-sectional area of each segment of the DOD printhead channel can then be chos...