How to transform reliability in ink jet: The need to control electric charge

                                         Guy Newcombe, CEO, Archipelago

                                         Guy Newcombe, CEO, Archipelago

In a previous interview with on this blog (23 January 2015), I commented that “The world of inkjet has been bedevilled by systems – often well-established systems – falling over, without their producers necessarily knowing why. Our understanding of the fundamentals, supplemented by use of highly precise measurement, helps us to avoid these traps”.

So I thought it was time to give an example of this “trap”?

Industrial printing systems used for wide-format printing are a good example. We find that companies regularly report a number of problems – notably (1) ghosting, (2) misting, and (3) ink landing on the nozzle plate. Taken together, these problems constitute a major challenge to achieving the desired levels of productivity and print quality. 

Printing companies hate this! They have to keep halting the printing process – often many times a day. The delays caused by fixing problems and then running checks before restarting the print run are a major source of inefficiency. The problems are particularly severe if you print on a web.

And how does an understanding of “fundamentals” help to overcome these problems?

These occurrences often cause companies a good deal of confusion, not least because of the large number of variables involved.  The scale of the problem varies with the printhead, the type of substrate, and the inks to name but a few. This is very frustrating for inkjet companies, understandably so, given the considerable resources that that the inkjet industry has invested in the development of inks, printheads, and systems. Our grasp of the fundamental science of inkjet has allowed us to see that companies often look for solutions in the wrong place. For example, common sense might suggest that the problems arise from the droplets coming out of the printhead in the wrong direction – yet we’ve seen that it’s common for the ejection process to be working well and yet the droplets end up in the wrong place.  This has led us to look elsewhere for a diagnosis.

The diagnosis

Because we’ve had extensive experience of printing with both charged and uncharged droplets, we realised that a major cause of printing problems was the presence of electrical charge in the droplets. This requires a different kind of solution.

What's our solution?

We’ve developed two solutions – one short-term solution and a long-term one.

We provide the short-term solution through consultancy. The key is to enable the client to understand precisely what they are printing. We use our precision instruments to characterise the scale of droplet charging for the different, inks, printheads and waveforms– and then develop a customised solution. This involves remedial action – dealing with the problem of electrical charge once it has arisen.

Long term solution

The long-term solution is not to remedy the problems associated with electrical charge once they have arisen, but rather to eliminate the charge from the process. 

Elimination requires modification of the hardware. To do this, we deploy our intellectual property – we have filed a patent for the technology essential for the process so that we can license it to our clients.

A focus on electrical charge might sound like a matter of mere technical detail – in the grand scheme of things, how important is this issue to the future of the inkjet industry? 

It is a matter of technical detail – but it’s also a fundamental issue.  Charged droplets can cause an inkjet system to fall over in minutes so they cannot be ignored.  As the number of printheads in operation grows, reliability becomes more of an issue and so controlling charge becomes critical.  Indeed, maintaining control of all the processes that are associated with droplet ejection becomes more important as the number of heads increases. Control of charge is a vital part of this.

Our experience is that, as systems become bigger, the recipe for success is to be on top of every technical detail and then control all the processes involved.  This is what we’ve done with charge and is our formula for success in reliable industrial inkjet.

To take inkjet to the next stage of development, the industry needs not only to continue to develop the printheads (P),  ink (I), and nozzles (N), it uses, but also to open up the new frontier entailed in the control of charge (C). Think PINC!

For more information on Archipelago