The term ‘inkjet printing’ is probably familiar to you. In fact, chances are that you probably have a desktop inkjet printer at your home. However, ‘thermal’ inkjet printers (the ones typically found in homes) represent only a portion of inkjet printing technology. In most industrial settings, a continuous inkjet printer is used instead. What exactly is a continuous inkjet printer?

What is continuous inkjet printing?

Continuous inkjet (CIJ) printing was actually the first inkjet printing technology developed – a good two decades before thermal inkjet printers were created. Since the 1950s, the fundamental concept behind its operation has barely changed, which is more of a testament to how reliable and effective the technology is.

CIJ printing starts with a high-pressure pump delivering ink from the printer’s reservoir to the nozzle. The printer nozzle continuously vibrates because of a connected piezoelectric crystal – a crystal that creates vibration when it receives a current supply. The vibration of the nozzle breaks apart the stream of ink into microscopic particles. The spacing of these ink particles can vary according to how quickly the piezoelectric crystal vibrates because of the current that it receives.

From the nozzle, the ink particles go through a charged electrode that creates an electric field. The current supply to this electrode turns on and off, resulting in an alternating series of charged and uncharged ink droplets.

The droplets then pass through another electric field, this time created by a charged plate. The ink droplets are repelled away from the charged plate at an angle determined by the charge status of each droplet. These repelled ink droplets then hit the printing substrate.  Uncharged particles simply go straight through the second electric field and enter a recycle stream that brings them back to the printer reservoir.

Where is it used?

Not many people may know about CIJ printing, but just about everyone has seen products of the technology around. Because of its superior printing speed, adhesion, and durability, CIJ printing is the most preferred method for marking product packaging with product codes, expiration dates, and barcodes.

If a product needs to bear markings that should not be rendered illegible under any circumstance – such as warning labels or hazard symbols – then CIJ printing is still the most reliable technology.

CIJ printing is even versatile enough for printing directly on food, such as meat and dairy products. Naturally, food-grade ink needs to be used with CIJ printers for such applications.

The applications of CIJ printing aren’t limited to consumer products. It has also been used to mark medical supplies such syringes, IV bags, and rubber tubes. Even NASA uses CIJ printing for parts that are meant to be used in space, which is quite a statement to the reliability of CIJ printers.

What are its benefits over other inkjet printing technologies?

1. Faster

The combination of the Rayleigh mechanism for breaking up the ink droplets and the electric field-propelled ejection of ink into the substrate makes CIJ printing extremely fast – up to a maximum of almost 200 meters per minute, or equivalent to around 120,000 drops of ink per second. For reference, even modern thermal inkjet printers are only capable of about half of that speed. This has made TIJ printing the method of choice for high-volume marking and coding requirements.

2. Better adhesion

Since all ink droplets that hit the substrate are electrically charged, the ink used in CIJ printing adheres exceptionally well to a variety of materials. It has a low tendency to smudge even on smooth surfaces such as glass or photo paper. Prints made using the CIJ method don’t fade or become damaged over time, which makes them excellent for products that can go through a lot of handling or be exposed to the outdoor elements.

3. Versatile

The superior adhesion of CIJ printing makes it a suitable method for printing on curved or uneven surfaces that can otherwise result in the ink pooling or smudging. Despite being an old technology, there is still a whole spectrum of different inks compatible with CIJ printers that can be used for different materials and applications. CIJ printing performs equally well whether it’s used to print on smooth, porous, absorbent, or biodegradable materials.

Summary

Despite the age of the technology, continuous inkjet printers are still alive and kicking. With so many commercial and industrial applications even until today, it has proven itself to be one of the most enduring printing technologies in human history.