Boosting the 'Jet' in Inkjet

  • By Eric Corzine
  • September 07, 2021
  • Insights
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As any inkjet engineer will tell you, a relatively small number of chemicals are used to formulate inks. As a result, having a deep understanding of how these chemicals all interact with one another and behave in different environments, and in different printing processes, is absolutely key to ensuring consistent and reliable print quality.

Dr. Josie Harries, Domino Group Program Director reveals how close examination of the jetting process in Continuous Inkjet (CIJ) printers helped to uncover the root cause of an issue which had puzzled the entire industrial coding and marking industry for decades.

World Class R&D at Domino

Domino engineers are constantly seeking new ways to advance our industrial printing products, solutions, and services. Our research and development (R&D) efforts include a strong focus on developing new and reliable ink formulations and looking at how we can optimize inks for different production environments that occur in industrial environments every day. These typically include temperature, humidity and any number of environmental factors that can affect ink viscosity and other factors.  

Different inks for different industries

Just as you would never put a racing fuel into an economy car inks must be optimized for their particular usage and environment. In order to achieve a clean, crisp code on a Beverage canning line requires a very different type of ink to that used for harsh industrial applications, like printing on cables or cement bags.

In order to ensure maximum reliability, our engineers have to take how inks behave under different conditions into consideration - and that includes any subsequent impact on industrial printer performance.

CIJ in Hot to Cold Environments & Everything in Between

Part of our research includes an ongoing project to better understand the jetting process in CIJ printers. We are researching how inkjet formulations behave in every type of industrial atmosphere from hot to icy cold; sticky to dusty - in order to reflect all the variables that could occur in customer facilities, so that we can better identify which ink formulations are most reliable.

 

Ink Particle Buildup, a Necessary Evil - Until Now

One specific area that our engineers have explored is particle build-up – that is, where small ink deposits accumulate on deflecting plates within CIJ printheads. The accumulation of particulate matter is an issue for manufacturers using CIJ printers. This necessitates more frequent cleaning, and, if left to build-up for longer periods, can cause downtime.

Particle build-up is inherent to all CIJ printers, but it is not often spoken about in the coding and marking industry. Historically, certain inks developed for use in inkjet printers have been more prone to build-up, and over the years, different printer designs have been developed to minimize the issue. That said, concrete evidence as to why the issue occurs, and a real understanding of how to overcome it, has always been missing.

Until now.

As the material generated during the build-up process is very small, it has been historically difficult to visualize. As part of our research, we sought to uncover the root cause of particle build-up by examining the phenomenon in extraordinarily close detail. To do this, our engineers collaborated with Cambridge University Institute for Manufacturing (IfM) to gain a deeper understanding of what was occurring by by truly studying the jetting process at the microscopic level.

Collaborating with IfM to gain a 'deeper' understanding

Working with the IfM, we conducted a series of high-speed visualizations to observe build-up occurring within the print head. The experiments used illuminating lasers and smoke to provide detailed imagery of the particles within the inkjet stream.

This incredible visualization revealed that the particle build-up, which has plagued our entire industry from its genesis, stems from small satellite droplets that break off from the main inkjet stream. Those droplets are subsequently charged by the electrostatic field generated by the deflecting plates.

Then, charged particles build up in the print head, resulting in the need for more regular washing. Only with regular washing, does it ensure that the printer keeps working. Without washing, the printer can require lengthier service. 

This groundbreaking visualization technique allowed our engineers to observe the phenomenon and monitor the behavior of the satellite droplets in different formulations - and with changes to the settings used to run the print head. This allowed us to gain a deeper understanding of which factors contribute to particle build-up. The full results, and more detail on the specifics of the project can be found in our joint paper with the IfM: Deflecting the Issue: The Origin of Nanoscale Material Build-up in Continuous Inkjet Printing.

Finding the root cause to an age-old issue

Our work with the IfM provided a route to understanding particle build-up, and by extension, the role that ink formulation plays in inkjet reliability. This has allowed us to work to optimize our ink designs to prevent build up occurring by avoiding chemicals that have a propensity to have this issue – we can use these techniques very early in the development process to screen out materials rather than discovering the issue late in the project. It has also allowed us to explore where we can develop in-house capabilities, similar to the visualization techniques employed by the IfM, so that we can conduct further research as part of new ink development processes. That way, we can continue to provide reliable solutions for our customers in the future, as and when new production processes arise.

The benefit of this research is two-fold: it helps the industry to better understand how to design printers that offer better uptime; and it informs the ink formulation process so that R&D teams can develop inks which will function reliably within specific printers, and in specific production environments, helping to reduce downtime and waste. This adds value for our customers from an efficiency and a sustainability perspective, and feeds into our company purpose, and commitment to helping our customers be sustainable and cut waste, while attracting, informing, and protecting consumers.

Discovering Groundbreaking Success - Again

Exploring the origin of particle build-up in CIJ printers is just one of the latest examples of R&D success that will benefit Domino customers and the coding and marking industry as a whole. It is also a small part of much wider efforts occurring at Domino to develop a better understanding of how printers perform - not only at the macro level, but at the micro level, and to uncover new and improved methods of developing reliable solutions, quickly and efficiently.

Collaboration, whether with the IfM, our Domino colleagues, or external partners, is key to our R&D efforts in this area – and achieves one of our core business values, and a key part of how we are working to build expertise within Domino. An issue, or idea, studied in isolation will only progress so far, restricted by the knowledge, experience, and technical capabilities of one entity. By working with the IfM we were not only able to extend our existing testing capabilities, but also benefitted from a broader knowledge base.

Collaborating outside of a specific industry or organization sparks creative innovation because everyone brings a unique set of skills to the table. That is why, across Domino, you will see our R&D teams working closely with customers, industry associations, and universities and other education institutions, to deepen our knowledge and understanding of the many factors affecting our industry, and those in which our customers operate.

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