A relatively small number of chemicals are used to formulate inks, and so understanding how these chemicals interact and behave in different environments, and in different printing processes, is key to ensuring consistent, reliable print quality.
In this article, Dr Josie Harries, Group Programme Director, Domino Printing Sciences (Domino), 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 coding and marking industry for decades.
R&D at Domino
At Domino, we are constantly seeking new ways to advance our products, solutions, and services to deliver the best performance and value for our customers. Our research and development (R&D) efforts include a strong focus on developing new reliable ink formulations and looking at how we can optimise inks for different production environments.
Achieving 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. To ensure reliability, it’s therefore important to consider the way an ink behaves under different conditions, and any subsequent impact on printer performance.
Part of our research includes an ongoing project to better understand the jetting process in CIJ printers. We are looking to examine how inkjet formulations behave in every type of atmosphere from hot to icy cold, from sticky to dusty, to reflect all the variables likely in our customers’ plants, so that we can identify which formulations make reliable inks.
One specific area that we have looked to explore is particle build-up – that is, where small ink deposits accumulate on the deflecting plates within a CIJ printhead. The accumulation of particulate matter is an issue for manufacturers using CIJ printers, as this necessitates more frequent cleaning, and, if left to build-up for an extended period, can cause downtime.
Particle build-up is inherent to 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 minimise the issue. That said, concrete evidence as to why the issue occurs, and so 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 visualise. As part of our research, we sought to uncover the root cause of particle build-up by examining the phenomenon in close detail. To do this, we collaborated with Cambridge University Institute for Manufacturing (IfM) to study the jetting process at the micro level, to gain a clearer understanding of exactly what was occurring.
Collaborating for success
Working with the IfM, we conducted a series of high-speed visualisations 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. The visualisation revealed that the particle build-up stems from small satellite droplets that break off from the main inkjet stream and are subsequently charged by the electrostatic field generated by the deflecting plates. Charged particles build up in the print head, resulting in the need for more regular washing to ensure that the printer keeps working.
The visualisation technique allowed us to observe the phenomenon and monitor the behaviour of the satellite droplets in different formulations, and with changes to the settings used to run the print head, so we could better understand 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.
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 optimise 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 visualisation 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.
Conclusion
Exploring the origin of particle build-up in CIJ printers is one of our latest examples of R&D success which will go on to benefit our customers and the wider coding and marking industry. It is also a small part of much wider efforts occurring at Domino to develop a better understanding of how printers perform, and to uncover new and improved ways of developing reliable solutions, quickly and efficiently.
Collaboration, whether with the IfM, our colleagues, or external partners, is key to our R&D efforts in this area – it is also 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 organisation 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.