Continuous Ink Jet Printers - By: Mae Alexander

Perhaps the best known method of non-contact marking and coding is continuous ink jet (CIJ). The continuous ink jet method is used commercially for marking and coding of products and packages. Using a non-contact process, continuous ink jet printers have become one of the most versatile and durable options for manufacturers. Small character CIJ allows codes to be applied in a variety of fonts, lines and direction and at a range of throughput speeds – more than 1,000 feet/minute and with code heights ranging from 1/32- inch to more than ½-inch. A small character ink jet printer can create lot codes, expiration dates, bar codes and graphics on a wide variety of primary packaging. Also key is that many small-character CIJ printers are portable and can be moved from line to line as needs arise.

In continuous ink jet printers, ink constantly flows through the system, but only prints when signaled to do so. Ink is pushed by air pressure from an ink cylinder to the printhead. The pressurized ink then enters the nozzle, where the tube carrying the ink passes through a ceramic ring. Pulses of electricity are sent to this ring from the control board. The piezoelectric crystal in the ring contracts with each pulse of electricity, squeezing the tube. These quick squeezes create a wave action in the ink. The wave action causes the ink to break into droplets shortly after it leaves the nozzle opening and enters the charge tunnel.

The destination of each of the ink droplets is determined by the control board inside the small character inkjet coder. When a droplet breaks from the ink stream, a positive voltage is applied to the charge tunnel. This gives the droplet a negative charge as it separates in the tunnel. The ink droplets then pass under the deflection plate, which has a fixed positive charge. Each droplet is given the precise charge that will deflect it to an exact location on the material to be printed. Those droplets not needed for printing are given no charge at all and are re-circulated back into the system for subsequent printing.

The vertical placement of each ink drop is determined by the printer. The horizontal placement is determined by the movement of the surface to be printed, such as packages on a production line. Characters are created in a dot matrix format with multiple dots creating a single character. The feed motion of the product is used to spray the numbers or letters one after the other onto the product. Since some evaporation of the ink solvent occurs during the continuous ink jet printing process, the viscosity of the ink is maintained by an automated control system which determines how much more solvent to add. The ink is kept at the proper consistency for easy flow through the printer and clean, crisp printed images.

About the Author

Videojet Technologies Inc. is a world-leading manufacturer of barcode printers, bottle printer, packaging printer and accessories for the wood printing industry. As experts in continuous ink jet (CIJ), thermal transfer overprinting (TTO), food grade ink, laser technologies & track and trace solutions, Videojet has over 275,000 units installed worldwide. Our global network of sales and service centers provides all regions with high quality service.

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