Continuous inkjet

Continuous inkjet – perhaps most widely used in the industrial coding, marking and labelling markets - can be designed using a binary or multiple deflection system.

Put simply, with a binary deflection system some of the ink-drops are charged and some are uncharged. It is the charged drops that fly directly onto the media, while the uncharged drops are ‘deflected’ into a gutter for recirculation. Whereas with a multiple deflection system (also known as raster imaging) the design is essentially reversed, so while the uncharged ink-drops fly directly into the gutter for recirculation, the charged drops are ‘deflected’ onto the media at different levels.

INK JET TECHNOLOGY

ContinuousDrop-on-Demand

Binary

Multiple

Hertz

Microdot

Deflection

Deflection

 

 

Elmjet

Videojet

Iris Graphics

Hitachi

Scitex

Diconix

 

 

Image

Domino Amjet

 

 

 

Linx

 

 

Thermal Piezoelectric Electrostatic Accoustic

Roof-shooter Side-shooter

Hewlett-Packard Canon

Olivetti Xerox

Lexmark

Squeeze

Tube

Bend Mode

Push

Mode

Shear

Mode

Siemens

Tektronix

Dataproducts

Spectra

Gould

Sharp

Epson

Xaar

 

 

Epson

Trident

Nu-Kole

 

 

On Target Tech.

 

 

Brother

 

 

 

 

 

Microfab Tech.

 

 

 

 

 

Philips

 

 

 

 

 

Topaz Tech.

 

 

 

 

 

 

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Meanwhile, another continuous inkjet concept - the Hertz concept (named after Professor Hertz of the Lund Institute of Technology in Sweden) - can be given separate classification because of its unique way of obtaining gray scale through a burst of small drops. By varying the number of drops laid down, the amount of ink volume in each pixel was controlled by Hertz, therefore the density in each colour could be adjusted to create the gray tone desired, making this ideal technology for high quality colour images at a stage where drop-on-demand quality could not really compete.

Drop-on-demand

But today, drop-on-demand technology can readily compete, and the majority of activity in inkjet printing currently available utilises one of two drop-on-demand methods: thermal and piezo (or piezo-electric). That is to say that the printing devices supplied by most of today’s manufacturers are equipped with either thermal or piezo print heads. This is mainly due to the cost effectiveness of this technology over continuous inkjet.

Thermal inkjet print heads receive signals from the control unit, which causes an internal heating device to heat up rapidly and boil the ink present to form a bubble. The heat increases until the bubble bursts and forces the droplet out through the nozzle onto the substrate at high speed. Droplet size may vary from half to full size by heating one or two elements respectively.

Piezo processing on the other hand, works through the piezoelectric effect. Here, currents pass through piezoelectric crystals or ceramic chambers. This causes the chambers to change shape, which squeezes ink from the nozzles. To produce larger droplets the voltage must be increased which displaces more ink, resulting in a larger droplet. Manufacturers have also experimented more recently with acoustic (also referred to as airbrush) and electrostatic inkjet, but these technologies are still very much in the developmental stage and few commercial products employing them are yet available.

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