Our Vice President of Technical Sales, Kevin McKell, explains what effect cleaning the web can have on the surface energy and why Vetaphone decided to become involved in web cleaning.
Vetaphone is renowned for applying surface treatment to the web – why did you get involved in the process of cleaning it too?
It was not a decision we took lightly. Web cleaning is a well-established and mature market with a range of respected manufacturers offering both contact and non-contact solutions. But we were finding increasingly that printers and converters were having issues with some of the substrates they were processing, and this was being reflected in the quality of work they were producing.
What was the problem?
When we investigated each case, we found the commonality was an issue with surface energy after the web had been cleaned. Standard procedure in the industry is to use contact web cleaning, which as its name suggests, picks up particles from the web on a roller and transfers them to the adhesive roll – but it does it by physically contacting the web.
What is the effect of this type of cleaning?
While the process is very successful, giving continuous cleaning of the web and removing particles down to 1-micron in size, there is a side effect in the form of reduced surface energy – and sometimes it’s a dramatic reduction. Unfortunately, in a bid to clean the web, many equipment suppliers and converters have lost sight of the reason they are trying to clean it – and that is to improve the quality of the end product.
But surely that’s not a bad thing?
Not at all, but you have to appreciate there are consequences for your actions. Every converter wants the web to be as clean as possible because it will improve the performance of downstream processes like printing, coating, or laminating. The problem is that in cleaning the web they can significantly reduced its surface energy. You have to get the two processes to work together, and to do that, you have to understand what each is doing, and how it is doing it.
Can you explain how this works in action?
I’ll give you two examples of what we found when we investigated the problem. The first converter had mounted the web cleaner after the corona treating unit. This had the effect of reducing the dyne level of the web from 44 when it left the corona station to 34 after it emerged from the web cleaner – and this is way too low for ink to adhere securely to the web. In the second instance, the converter had mounted the units correctly, web cleaner before corona treater, but the cleaner was depositing so much silicon onto the web that the corona unit needed more power to deliver the surface energy required to reach the correct dyne level.
So, is it at this point that Vetaphone took an active interest in web cleaning?
Yes, because as the pioneers of surface treatment we were in the best position to understand the science involved and be able to develop a practical solution. The key element of our web cleaning system is that it is designed to work with the corona treater without affecting the surface energy of the web. The two processes need to complement each other so that the web is delivered in the best possible condition for printing, coating, laminating, or whatever other process is required.
So, what makes the Vetaphone web cleaning system special?
We set out to integrate it with our existing portfolio of products rather than manufacturing something as a standalone product. This offers customers a single source of supply and the benefit of operator control that is combined with the corona treater. Like all Vetaphone technology, the web cleaner is designed for maximum flexibility, and can be mounted in various locations to suit any press configuration and web orientation.
What are its specifications?
It’s designed for narrow web applications where we currently hold a global market share for corona treaters in excess of 80% – so you could say we are playing to our strength! The Vetaphone web cleaner can be single- or double-sided, is available in four standard web widths from 350mm to 570mm and has a maximum web-driven operational speed of 250m/min.
How does it work?
Our design and clever use of high-quality elastomer cleaner rolls and perforated adhesive rolls makes sure that all contamination is removed. The side-access to the unit allows the operator to remove the used sections of the roll sheet quickly and easily, and the top opening gives access for web threading and cleaning of the elastomer rolls. To make it even easier, we have added a quick-release device that allows the adhesive roll to be changed without the need for tools, and the cartridges have a self-locking system to prevent any movement during operation. Also, the active anti-static system prevents any possibility of re-contamination after the cleaning process has finished.
You mentioned integrated control…
Yes, our web cleaner can be linked to the Vetaphone iCorona Generator, which means there is no need for any additional operating system. This improves production efficiency and reduces stress on the operator because web cleaner control and maintenance is fully integrated with our corona system on the same module. It means that one screen provides all the information required for both web cleaning and surface treatment.
Is this really valuable?
Yes, it is, because the console alerts the operator to all maintenance requirements, provides him or her with fault diagnosis, and also acts as an instruction manual. It has prompts built-in for paper changing and roller cleaning, so all the operator needs to do is monitor one control screen. Feedback from users include comments like: ‘it’s a dream to operate’ and ‘it takes one more variable out of the equation’, so we know the value of its clever design.
One final tip for converters?
The most important house rule of all is: ‘locate the web cleaner before the corona treater’ – you must clean then treat – if you don’t, you risk reducing the dyne level on the web by anything from 10% to 30% or even more – and that will seriously affect your production quality!