Problem solving based on accurate technical models of coating and printing

Too many people have claimed that coating and printing are arts not sciences. Or they claim that if they are sciences then they are too complex for helpful analysis. So they rely on "Old Joe" who has the "magic fingers" to tweak the process and get the product out of the door.

I completely disagree. Most current coating and printing techniques are readily understood with help from a suitable computer model. Not the sort of model used by academics (though my academic colleagues at U. Leeds have wonderful models that we use for deeper analysis of issues), but hands-on modellers where you can see what happens when you change the web speed or viscosity, when you change the angle of your slot coater, when you change the speed ratio of your rollers, when you change the tension of your web, when you change the thickness of your screen-print stencil, or when you change the hardness of your flexo rubber.

Coating

So my colleagues at RheoLogic and I developed TopCoat. TopCoat covers all the relevant coating techniques (roll, curtain, slot, knife, dip...), has a powerful drying modeller and has models of many types of defects (causes and cures) and explanations of the flow and surface effects relevant to coating. A lot of complex science is packaged up so that you can have the software next to your production machines and trouble-shoot issues live on the screen. They are also used for training the development team and production staff in the subtleties of the coating processes. If you can't afford to have your own copies (though normally you pay back the price of a copy with the savings from your first production trial that uses the software) then I or my RheoLogic colleagues can help you troubleshoot your processes using our own copies of the software. We very much believe in using the tools we developed.

Web handling

The way that webs wrinkle or form poorly-wound rolls, or curl during lamination, or scratch etc. often seem mysterious. With advice from three top web-handling consultants, Dr Dilwyn Jones, Dr David Roisum and Timothy Walker I wrote TopWeb as part of the RheoLogic product range to capture as much of the theory as possible and make it possible for non-experts to diagnose their problems. Timothy Walker has generously put a lot of his expertise on-line at WebHandling.com and the combination of his lucid explanations with the hands-on calculations of TopWeb is a particularly effective method of troubleshooting. If you need a real consultant on web-handling then I recommend that you call in Jones, Roisum or Walker. But within the context of a broader project I can use TopWeb to help advise on web-handling issues.

Printing

Screen printing is, sadly, a prime example of the triumph of art over science. Many printers continue to insist that only their instincts and their magic tweaks to the press can provide the answer. In fact, the whole process is readily understandable and done properly requires no magic tweaking. Most of the problems are self-induced: by insisting, for example, on using the wrong stencil, then the ink has to be changed which causes other problems which then have to be fixed with higher squeegee pressure which in turn ...

By making sure that the mesh does the metering, the stencil does the shaping and the ink does what it does best, then the printing process is very straightforward. All this has been described by me in numerous articles for the screen print press and in the eBook I co-authored at MacDermid Autotype with Anna Harris, David Parker and Tricia Church How To Be A Great Screen Printer (6MB pdf). My thanks to MacDermid Autotype for permission to add this download to my website.

Similarly, there is a lot of mythology involved in flexo-printing. With my colleague ( Dr Nik Kapur at U. Leeds I developed a simple animation of the flexo process which provides many insights into what is going on during the crucial ink transfer step.

Printed electronics

There has been an extraordinary amount of misinformation, unrealistic dreams (remember when OLEDs were going to be produced reel-to-reel on inkjet printers?) and wasted effort in trying to create viable printed electronics devices such as displays or organic photovoltaics. As a hard-headed skeptic I have often had to break the bad news that a favoured approach simply could not work because it went against the laws of physics. The bad news can be the precursor for good news. By making sure you don't waste resources on techniques that will never work, you can focus on methods that will work. With the right combination of coating and printing modellers it is relatively straightforward to show why things will or will not work.