Monthly Archives: June 2017

Inkjet Printing Basics CIJ vs DOD

When conceptualizing inkjet technology, it is incredibly easy because it is essentially a digitally controlled ejection of drops of fluid from a print head onto a film or substrate. The manner in which the ejection happens, varies in two primary ways. The first being industrial inkjet, and is most commonly referred to as CIJ or Continuous Inkjet, where the second way to classify it is drop-on-demand inkjet. Variants of each of these styles are numerous and generally are only initiated for unique solutions.

Continuous inkjet ejects drops continuously, where the droplets are directed directly to the substrate, or in some instances to a collection tank for recirculation, recycling, or reuse. Drop-on-demand only produces and ejects droplets when required.

Continuous Inkjet

Continuous inkjet is stigmatized in the printing industry as a primitive or amateur type of printing. Continuous inkjet printers account for roughly 10% of the printer sales in North America in 2016. This is primarily and almost exclusively used in the marking and coding of products and packages, where high volumes and fast line speeds are critical to manufacturing process performance. CIJ utilizes a pump which pushes fluid from a reservoir through small nozzles to produce a continuous stream of droplets between (50kHz and 175kHz) via vibrating piezo print head crystals. The print quality and resolution is determined by how the droplets are charged through an electrostatic field, and deflected using a magnetic plate or field. The charge on the droplet, the magnetic field strength both determine where the droplet lands on the substrate, or if not charge is applied, the droplet will be directed to reflow through the reservoir conserving and recycling the unused ink. One of the unique benefits of CIJ printing is the fact that the droplets are pumped through the system at speeds often ten times faster than other methods which enables the substrate to be printed upon from a further distance away. Finally, the benefit of using a solvent based ink, allows for compatibility with a wider range of substrates including those with high surface energies.

The main drawback of CIJ is that most people consider this technology to be bad for the environment due to solvent being driven off in the curing process. While, this may be true, often times the alternative method of printing these labels or specialty signage have a far worse impact on the environment.

In the above image, pressure (red arrow) is applied to the heating plate (orange outline) in order to force the droplet of ink out through the print head nozzles.

Drop-on-demand inkjet

DOD inkjet is by far the most common and broadest classification of inkjet printing. This is most commonly used by companies such as Hewlett-Packard, Fujifilm, Lexmark, and Canon. As the large brand names suggest, these are most commonly used in consumer products such as desktop printers, but in the recent history has been proving to be useful in industrial printing as well. DOD print heads such as, thermal, piezo, and electrostatic use large pulses of pressure, with the differentiating factor being how the pressure is generated. Many companies may consider MEMS to be a unique method of drop-on-demand printing, but in the end it is still a subcategory based upon piezo or thermal architecture.

DOD droplets can be formed by rapidly heating a resistive element in a small enclosed chamber containing the ink. In this scenario the heated element is increased to 350°C to 400°C, which will cause a thin film of ink above the heater to vaporize. The vaporization causes a bubble to create a pressure pulse that forces a droplet of the ink through the print heads nozzle. Upon relaxation, the small chamber is then backfilled with more of the ink which will then be jetted through the nozzle onto the substrate as well.

The greatest advantages of DOD inkjet are the ability to create extremely fine droplet sizes which translate to resolutions observed greater than 1000p. Additionally, the high nozzle density due to the creation of droplets via pressure allows for more compact devices, lower print head prices, and reduced production costs. The main disadvantage is most commonly stated to be the limited inks available for vaporization. Each of the components in an inkjet droplet must be able to withstand high temperatures during vaporization without being adversely impacted upon solidification on the printed surface.

Inkjet Printing Technologies

After the 1990’s inkjet had worked its way into nearly all households through its printing presence in consumer benchtop printers as a low cost, reliable, fast, and convenient method for printing anything from digital files, photos, or screen shots. It has come a significant distance since its advent in the 1950s, in commercial products such as medical strips and chart recorders. As the industry has seen success the technology spread throughout the 1970s, into the widely recognized printing technique that exists today.

In theory, inkjet printing is simple. A print head ejects micro droplets of ink, carrier, and water onto a substrate (paper, vinyl, PET, etc.). When executing these techniques, companies have spent decades and countless millions practicing their disciplines in this skill. Piezo and thermal print heads are the most common when it comes to jetting UV inkjet or water based latex inkjet ink.

Taking into account the complexity of the practice of inkjet printing, what drives the industry to adopt these techniques is the wide range of applications that are available. Initially, it was seen as a drop on demand product, which can produce any color gamut available without pre-blended colors or a unique colored thermal transfer ribbon. As this technology continues to develop, it is turning into a wider range of applications including educational and industrial where professionals need to accurately deposit precise amounts of materials. Additionally, inkjet printing laid the ground work for the 3d printing technology that is still premature and developing today. The list of industrial uses for inkjet technology appears endless and is only being improved by reduced manufacturing costs, higher quality materials (such as outdoor durable jetted materials, 3d printed materials, and accurate doses), printing on difficult surfaces, reduction of waste, and rapid prototyping.

Benefits of Inkjet
Automotive coatings Replaces spraying or dipping, thereby reducing waste and increasing coating uniformity.
Plastic part decoration Non-contact accommodates curved surfaces. Improved print quality over pad or screen printing. Digital eliminates requirement for inventory of screens or pads, resulting in faster prototyping and wider variety of designs. Process color capability reduces the number of ink colors that must be stocked.
Conductive patterns Minimizes waste of costly materials; very suitable for short runs.
Rapid Prototyping Rapid formation of three-dimensional structures designed by using computer software.
Variable information Allows fast changing of the printed information, unlike analogue printing methods which require formation of new hardware (e.g., screens in silk screen printing).
Ceramics Minimizes setup time, eliminates requirement for inventory of screens.

(Magdassi, 2009)

The introduction of inkjet printing in industrial markets has proven to increase manufacturing environments with often more than a modest improvement, or in some cases revolutionize the production and identification of materials and products.


Pardon our mess, we are currently remodeling out website. Check back this week for news and updates regarding Thermal transfer printing. Our expert staff is preparing a fantastic article about the fundamentals of thermal transfer printing, as well as improving chemical resistance of the THT print.

From there, we will have our most senior staff provide us with an article on ink jet applications and the current limitations of eco-solvent inks.