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To Contact…Or Not To Contact

Product News Friday, February 11, 2011: Meech International Ltd.

Communication and web cleaning might not appear immediately to have anything in common, but in both cases there are times when it is good to be in contact and other times when it’s best to leave a little distance. The skill, in each scenario, is to know which is right. UK manufacturer Meech International makes contact and non contact web cleaning systems for a wide variety of applications and markets. Below it looks at some of the issues that should be considered when purchasing a system.

“The drive towards lower wastage and higher levels of productivity can be seen across a huge number of industries, as companies seek to increase the efficiency of existing equipment in order to improve profitability, without incurring the cost of investing in a new line,” says Adam Battrick, business unit director, cleaning systems.

One factor above all else determines whether a company should invest in contact or non contact technology; if the substrate being handled is in any way prone to marking then the later is the sensible choice. There is another influence - the general desire by companies to have as few objects as possible touching the substrate, especially important in the pharmaceutical packaging, LCD and plasma screen industries.

“Since the autumn of 2009 we’ve seen a surge in orders for web cleaning systems. During 2010 companies have been investing increasingly in non contact web cleaners because they want the maximum flexibility in the future - equipment should not dictate what types of material they can run on a particular press or production line. This trend is quite noticeable in some areas of the graphic arts market and has started to emerge in the label sector.”

When selecting a web cleaner, whether contact or non contact, one of the crucial factors is to make sure the cleaner will break the boundary layer of air that is entrained by the moving web, holding contamination firmly to the substrate’s surface. To break the boundary layer, different systems use varying technologies, which may rely on powerful airflows, air turbulence or actual contact with the web.

In the rotary label arena, it is common to see web cleaning systems that are based on a tacky [elastomer] roller, which is driven by contact with the web. Contaminates picked up by the roller are transferred to a second, more adhesive roller. The technology has many benefits; it is relatively easy to install and on the whole provides adequate results.

The main gripes from users are the cost of buying the adhesive sheets and the time needed to replace used sheets when they reach a certain level of contamination. If not replaced, the cleaning performance deteriorates. For example, if the roller picks up particles from the web that adhere to the same spot during each revolution, then the system normally becomes ineffective at removing dirt from that one area.

Some form of static control, whether passive or active, is normally incorporated just after the cleaning process in order to reduce the risk of recontamination of the web. Indeed, regardless of the cleaning technology, any system should have electrostatic control, preferably active, or the web can become re-contaminated quite quickly.

Also within the category of contact cleaning systems are those that use brushes to remove dirt and debris from the web surface and those that rely on some form of vacuum. The former are probably the least commonly found systems but there are several companies offering vacuum based options.

In these systems the web comes into contact with some part of the cleaning equipment. In the case of the Meech Tornado, the web contacts a highly polished stainless steel faceplate, which creates a turbulence that breaks up the web boundary layer. In conjunction with active static control, this releases contamination into the vacuum slot.

Apart from purchase and installation costs, potential users should examine in detail several areas during evaluation. The effectiveness of systems can vary dramatically so make sure that if you need to remove particles down to a certain size, for instances less than five microns, that the equipment is up to the job.

Systems can typically be tailored to suit a particular application, for example a pre-filtration facility will avoid fibres passing through the vacuum unit (useful if the contamination is fibrous or abrasive), while for heavily contaminated substrates a filter bag with a large capacity will reduce the number of changes that have to be carried out.

Check carefully any running costs eg electricity usage and consumables, plus the vibration and noise levels, which can be sufficient in some cases to effect the positioning of the equipment in relation to operators or other equipment. Ease of access and maintenance requirements should not be ignored.

“Of course, price is also an issue but this is such a wide area that it’s impossible to give much of a guide,” says Adam Battrick. “Normally, non contact systems require a greater investment than contact systems due to the complexity of the technology involved. Some contact systems can be purchased for as little as £5,000 depending on web width and whether you wish to clean one or both sides of the substrate.”

Return on investment is an obvious consideration and Meech has been conducting some extensive research along these lines following its recent launch of the non contact web cleaner, ShearClean. This has included studying the effects of installing ShearClean on a 1,200 mm wide, ten-colour Cerutti gravure press at a European printer.

“We examined the monthly costs incurred due to press downtime and wastage caused by damaged/worn doctor blades or cylinder rollers, debris in the ink pan, streaking and hickies plus web breaks. The customer had kept a careful record of costs prior to the installation and during a normal four week period it would expect sixteen stoppages due to the reasons above, which equated to 4,000 metres of wasted material. In monetary terms this resulted in a combined (downtime/material) average monthly potential sales revenue loss of £13,000.

“Since equipping the Cerutti with ShearClean, press stoppages have been reduced to an average of six per month and wastage has been cut to 1,500 metres. The result was an increase in monthly sales revenue in the region of £8,000. Along with the customer, using their sales revenue margin, we calculated a return on investment for the web cleaner of under nine months, with the added benefit that the printer is able to provide a faster service to its clients...a good message to communicate.”