The inkjet printing sector is filled with different technologies that excel in their own distinct ways. Despite differences in build and title, all inkjet printers are built around the same basic concept—precisely expelling small ink droplets from a printhead to place images, text, and codes onto a variety of substrates. 

Since first arriving on the market in the 1950s, inkjet printers have become an integral part of the coding and marking field. Today, the entire inkjet printer sector is valued at $80.4 billion and is projected to continue growing at 11.4% CAGR. This high profitability is largely driven by the variety of inkjet printer types with unique abilities and application specialties.

Some of the most high-profile inkjet printer models include:

• Continuous inkjet (CIJ) printers.
• Thermal inkjet printers.
• High-resolution piezo printing systems.

With all of these different inkjet printer types on the market today, many consumers are left wondering how they differ in build, application abilities, upkeep, and more. To simplify, inkjet printers can be separated into two categories:

1. Those that use continuous inkjet systems
2. Those that use drop-on-demand (DOD) systems

Here’s what you need to know about CIJ vs. DOD hardware differences as well as application specialties for each.

CIJ vs. DOD: The Hardware Differences

As we touched on above, inkjet printers create images by expelling ink out of a printhead in a precise, controlled manner. The difference between CIJ and DOD printers lies in how the two systems propel the ink droplets. Based on this difference, CIJ and DOD printers have separate specialties and marking possibilities.

How CIJ Printers Work

CIJ printers mark substrates by pressurizing ink into a continuous flow. Within a CIJ printer are two cartridges—one filled with ink and one filled with solvent/make-up. These two cartridges filter into the main reservoir where they combine into one printable mixture. Adjacent to the reservoir is a pump that pressurizes the mixture so that it moves toward the printhead. 

When the ink reaches the printhead, an element uses vibrations to convert the stream into individual drops. An electrode plate then electrifies the drops, enabling them to be directed toward the substrate. Once charged, the drops are propelled from the printhead and onto the substrate to form the intended image. The remaining ink is then directed toward a gutter which reroutes the stream back to the reservoir to repeat the process. 

With the help of this continuous ink flow, CIJ printers can mark substrates at fast speeds without interruptions. 

How DOD Printers Work

DOD printing became popular in the 1980s with the introduction of the valve jet printer, which was the original case coding system. The drop-on-demand association materialized simply from not knowing what category this hi-resolution printing fell into. This is a prime example of how many printing systems are oversimplified and placed into either the CIJ or the DOD categories simply because these are the two original acronyms used in the coding and marking industry. Where valve jet printers were once considered hi-res, technologies such as piezoelectric printing have increased the resolution printing capabilities of DOD systems. It’s also important to note that what each company defines as DOD printing has changed, especially in the last 10 years.

Drop-on-demand printers mark substrates by propelling ink one drop at a time. In contrast with CIJ machines that use the same method to create continuous ink flows, DOD printers perform the printing process in a variety of ways, including through the use of heat, electricity, and vibrations. 

Due to this mechanical diversity, there are many different types of DOD printers on the market today. However, two DOD categories surpass all others in popularity—thermal DOD printing and piezoelectric DOD printing. 

• Thermal DOD printing utilizes heat to move ink drops from a cartridge and out of a nozzle in a controlled manner. Within a thermal DOD cartridge lies a series of heating chambers. To move ink from the cartridge, the chambers emit heat to create a bubble. As the bubble expands, the pressure causes the ink to move from the cartridge and out the nozzle onto a substrate. Once the ink is expelled, the bubble collapses, creating a vacuum effect that begins the process again.
  
• Piezoelectric DOD printing utilizes vibrations to move ink drops from a cartridge and out of a nozzle in a controlled manner. Like thermal DOD cartridges, piezoelectric ink chambers are lined with elements that propel ink toward a nozzle. Instead of emitting heat, however, these elements generate vibrations. In response to the vibrations, the ink is separated into droplets and pushed out of the nozzle. Given that the vibrations are caused by precise electrical charges, piezoelectric DOD printers provide users with a great amount of control over droplet size and speed. 

Note about piezoelectric printing: It’s important to note that piezoelectric technologies are not exclusive to DOD printing. In fact, piezoelectric elements are often used in CIJ printheads to oscillate the ink into individual drops. However, that does not change how the CIJ printer is classified, as the printer is still expelling ink due to the continuous inkjet principle. 

CIJ vs. DOD: Application Specialities

CIJ and DOD printers use very different methods to create text, codes, and other images. These mechanical differences impact several mechanical qualities, including:

• Printing speed.
• Possible line placement.
• DPI-resolution.
• Environmental resistance.

Generally speaking, CIJ printers weigh around 60 to 90 pounds and can print at uninterrupted high speeds 24/7. They also frequently have a wide operating temperature range, as they don’t rely on heat to mark substrates. Due to their large machine size, speed capabilities, and environmental resistance, CIJ printers are often placed on fast-moving production lines to code materials with traceable markings like lot codes, expiration dates, barcodes, etc. However, they are often limited in resolution capabilities, as most CIJ printers print at around 60-100 DPI.

As such, CIJ printers are commonly utilized to place codes on:

• Food packaging.
• Beverage bottles and cans.
• Pharmaceutical packaging.
• Wires and cables.
• Chemical packaging.

By nature, DOD printers come in more varieties than CIJ printers. Under the DOD umbrella are many different printer types, most notably including thermal inkjet printers and high-resolution case coders. 

Compared to CIJ printers, DOD machines can form larger ink drops for higher-resolution codes. This is very useful when creating markings like barcodes and data matrices that must be machine-scannable. The printheads on DOD machines can also be larger than those on CIJ printers, allowing for bigger images such as brand logos. However, DOD printers are more difficult to move along production lines compared to CIJ printers. They also cannot print down or up, limiting their line position possibilities.

Common DOD applications include:

• Printing logos on boxes.
• Placing traceable markings on both porous and non-porous substrates.
• Marking shipping containers.

Looking for More Info on CIJ and DOD Printers? Stay Tuned to C&M Digest’s Coverage

The modern coding market is filled with countless hardware choices and coding technologies. Just within the CIJ and DOD fields lie thousands of models with diverse printing capabilities and mechanical properties. Fortunately, you have a source that can help you make sense of these machines and printer types. C&M Digest is here to help readers learn about the different facets of the industrial printing industry.

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