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Servoing Method for Ink Jet Head and Ink Systems in Multinozzle Environment

IP.com Disclosure Number: IPCOM000046168D
Original Publication Date: 1983-Jun-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 3 page(s) / 48K

Publishing Venue

IBM

Related People

Irwin, JW: AUTHOR

Abstract

This article describes a method for locating and maintaining a print window in which a multinozzle ink jet head can be safely operated. Once the print window is determined, several interacting servo loops are used to return the head to the window for proper operation. In order to identify the print window, the following conditions must be met:

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Servoing Method for Ink Jet Head and Ink Systems in Multinozzle Environment

This article describes a method for locating and maintaining a print window in which a multinozzle ink jet head can be safely operated. Once the print window is determined, several interacting servo loops are used to return the head to the window for proper operation. In order to identify the print window, the following conditions must be met:

1)The streams are satellite-free for proper charging. 2) A phase window is present in which data to the head can be changed. 3) The droplets are breaking off from associated streams uniformly across the head.

The procedure is that at start-up the print window is determined and that during operation the head is forced to remain in the print window.

Shown above is a flow diagram for determining the print window.

The process ensures the setting of optimum crystal drive, optimum ink stream velocity, and optimum phase of charge electrode signals. Initially at start-up, an initial crystal drive is set. Immediately thereafter, an average time of flight (T.O.F.) or ink stream velocity is set. Both of these steps 10 and 12 are done without any check on their correctness. The values are picked from past experience. Next, the crystal drive is lowered in step 14 to a minimum voltage that will guarantee that it is less than the optimum voltage.

The servoing process step 16 tests and logs the charge placed on droplets in each stream as a function of the phase of the charge electrode signal within a charging window or range. The charge window is divided into l6 possible charge electrode signal phases. As each phase is tested for each nozzle, the data is recorded. Then the crystal drive is incremented one voltage unit by step 18, and new data is tested and collected for each of the nozzles.

When the optimum crystal drive voltage is reached, most of the charge signal will be applied to droplets in the streams near the centerpoint of the charging window. Process step 20 for selecting the optimum crystal drive analyzes all the charge value and phase data for the various crystal drive voltages. When it detects that most of the charge dro...