Research Academics  
 
   
 

A Micromachined Continuous Ink Jet Print Head For 
High Resolution Printing

 

Contact Person : Dipl.-Ing. Biswajit Mukhopadhyay

 

Introduction

For applications like printing machines high image quality and a short printing time are necessary. A high resolution (1200 dpi) ink jet print head based on the principle of continuous ink jet printing (Fig. 1) is presented. The print head consists of a multinozzle print head, a charging electrode array, and an array of ink shields to drain off the unused ink.

Operation Principle

 Fig.1: Operation principle of a continuous ink jet print head

Design of the nozzle array:

The nozzle array consists of 28 pyramid shaped inlets each of them with a polysilicon membrane, a single nozzle with a diameter of 5 µm, and two V grooves for the ink supply. The thickness of the silicon wafer is 390 µm and the size of the 2.5 µm thick polysilicon membrane is 25*25 µm2.

Manufacturing Process

Fig. 2 Illustration of the manufacturing process

  

Fig. 4: SEM micrographs of the nozzle array (without pyrex glass)
a) Section of the nozzle array with pyramidal inlet and 2 V-grooves
b) Single nozzle (diameter 5 µm)
c) Cross section of one membrane with a nozzle

Design of the charging electrodes:

SEM micrographs of the charging electrode array and the fabrication process are shown in Fig. 5 :

 

Fig. 5 Charging electrode array
a) Fabrication process
b) Front side (section) with metallisation
c) Cross section of one charging electrode

Design of the ink shields:

One possibility to realise the drain off of the unused ink is presented with an array of 28 ink shields
(Fig. 6).

 

Fig. 6 An ink shield
a) Fabrication process
b) Cross section of one ink shield
c) The ink shield in detail

Results and Conclusions

Experiments with the nozzle arrays have shown that an ink pressure in the range from 1 MPa to 1.5 MPa is enough to reach the needed drop velocity of 20 - 30 m/s. The print head in function is shown in Fig. 7.

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Fig. 7 Photographs of the print head in function (used frequency 800 kHz)

Fig. 8 Drop velocity as a function of the applied pressure

One of the main problems in such ink jet systems is the jet directionality. It depends on different factors like the misalignment of the nozzle, the nozzle design, and mechanical deformations. It was shown that a high resolution ink jet print head could be realised using silicon bulk micromachining. The first experimental results encourage to a further development of this microsystem.