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Need To Know

Static Control Technology

The issue of static and its impact on print quality has been ever-present. Russ Hicks discovers that the latest wave of anti-static technology could save you significant time and money

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Meech has an extensive range of static control technology that is manufactured right here in the UK

Controlling the forces of nature

Printers will, I am quite sure, fully appreciate that clean sheet separation, optimum sheet travel, and exceptionally high production speeds are only possible if your printing stock is free of electrostatic charges.
This becomes especially important when light grammages, coated materials, metallised boards, and plastic films, all of which have increasing degrees of static holding retention, become the substrate of choice.

Static can cause in feeder trip-offs, print voids from surface contamination, ink offset, or poor sheet jog in the delivery.

Static electricity is defined as a non-moving, non-flowing electrical charge. Static electricity becomes visible and dynamic during the brief moment it sparks a discharge, and for that instant it is no longer ‘at rest’.

What are the causes?

Why do we get a build up of static electricity, where does it come from? Steve Ennew, technical sales manager at MPL, RMGT B1-format press distributors, offers this addition to our physics lesson: “To begin with, there is the potential for static issue with improper grounding of equipment. This will result in the inability of the metal parts of the equipment to effectively neutralise charges. It will not eliminate static electricity, but properly grounded machinery will help drain-off and dissipate large charges, making the problem much more manageable.

Steve Ennew, technical sales manager at MPL, says: “there is the potential for static issue with improper grounding of equipment”

“Control of humidity is also important. Low humidity, or exceptionally dry, ambient moisture levels in substrates can encourage static build-up. Sufficient moisture is necessary to help dissipate static by raising conductivity. Low moisture paper, either by design or due to exposure to a dry environment, can be especially problematic. Coated web papers, manufactured to lower moisture content, may also be more susceptible to static charge when converted to run sheet-fed.”

Ennew continues: “The use of pressure and contact within the printing process is the next issue: the greater the contact area between the paper and other surfaces, the higher the potential for electron exchange and static build. Exceptionally smooth, gloss-coated papers with a greater contact area may be especially difficult to separate when a static charge is present.

“Temperature is certainly going to be a factor. Winter months and colder temperatures bring dryer climates and therefore higher potential for static. Thinner air at higher elevations also tends to be dry and does not consistently hold temperature, resulting in humidity fluctuations. Colder paper tends to be less conductive and more prone to static build than warmer paper properly acclimatised to pressroom temperature.

“Finally there is what can be described as a ‘combination effect’. Certain different materials or objects with variable levels of static charge can create a cumulative effect causing very high static charge.”

Effective management of all of these issues is of course the answer. Ennew offers these solutions: “Machinery should be grounded to a steel rod driven into the ground. This could be as deep as eight feet, depending upon voltage currents, local electrical codes, and machine manufacturer specifications. A properly grounded machine will help dissipate high charges of static electricity from semi-conductors such as coated paper.

“With machines properly grounded, metal core tinsel can then help to dissipate static by induction. The tinsel should be tightly stretched approximately 1/8” from the paper surface without contact. It is best placed across the pile at the feeder head, at the point of sheet separation and across the feed-board where adequate air space exists under the sheet. The tinsel should then be attached to a properly grounded press or other conductive object.”

Ennew also highlights another key area to investigate: “Electronic static eliminators, or neutralisers, are also now widely used. These use a high-voltage discharge to ionise the surrounding air. The ionised air acts as an electron source which, in turn, neutralises the static charge on the paper.

“In-line air ionisers are simple to install in the feeder blower line and very effective if installed properly. As the air blows between the sheets, the paper surfaces build up similar, or like, charges that now repel each other, encouraging sheet separation. Annual replacement of these ionisers is recommended in order for them to remain as effective as possible. Regular maintenance is also recommended as far as cleaning air blower filters and blower heads to ensure optimum sheet separation.”

Ennew also explains: “Anti-static or silicone sprays increase conductivity and minimise excessive contact from friction by applying a thin silicone or soap-based coating to the machine components that transport the material. Application to contact points such as the feed-board, transport tapes, and wheels can also be helpful.

“A properly climate-controlled pressroom includes humidification that aims to maintain 52 percent Rh at 21°C for European countries. Ambient relative humidity below 35 percent Rh can adversely affect paper and decrease conductivity, which results in a greater potential for static,” says Ennew.

He adds: “Paper, properly acclimatised to recommended pressroom temperature also has a better chance of running static-free compared to cold paper. Paper can be properly acclimatised to pressroom temperature without unwrapping—this maintains the relative humidity of paper consistent with its original moisture content.

Paper can be properly acclimatised to pressroom temperature without unwrapping

“Static is a common problem in web heatset sheeting and post-press converting due to the extremely low moisture content of the paper after drying at high temperatures. Re-moisturising the web after the chill rolls with a mix of water, silicone, and liquid fabric softener can further increase conductivity and reduce surface contact from friction, ultimately minimising static while helping the paper re-acclimatise to an ambient environment.”

Readers will note that there are numerous websites offering anti-static products and solutions, which effectively neutralise the presence of static electricity. It is important to note, however, that static electricity is only managed and not entirely eliminated. Semi-conductive materials such as coated paper will always be susceptible to static if once again subjected to the adversities of high contact through pressure and friction, and/or low humidity.

Commercial products

For its take on static solutions, press supplier Heidelberg offers what it describes as progressive solutions such as Static Star Compact and Static Star Advanced to reduce the electrostatic charge of sheets and enable high print production speeds to be achieved.

Heidelberg’s Static Star Compact is designed for everyday substrates such as paper, while Static Star Advanced is for difficult stock

Jim Todd, sales director, explains: “Static Star Compact is designed for everyday substrates such as paper and card, while Static Star Advanced is recommended for particularly difficult printing stock such as labels, light grammages, and coated materials.

“For applications with the most challenging substrates, such as metallised surfaces, in-mould labels, or thick PVC, Heidelberg offers the Foil Package. This includes all electrical components of Static Star, additional de-ionised blast air units on the feeder, and special sheet travel sensors in the printing units. The package delivers excellent reliability in production with printing stocks that are susceptible to the greatest electrostatic charges.”

The package delivers excellent reliability in production with printing stocks that are susceptible to the greatest electrostatic charges

Once again, the good storage of paper is highlighted, as it is important in helping to reduce and control static in printing. Ideally, pallets should be kept in their packaging until one hour before use and the temperature between the paper store and pressroom kept in parity. If there is a large difference in temperature, the paper should be given a period of time to acclimatise in the pressroom.

Humidity will also impact on paper; paper manufacturers specify minimum and maximum RH levels and printers are advised to keep within those limits and use humidifiers if there is a specific issue or if they handle more sensitive stocks such as woodfree papers, thin papers, medical papers, Bible paper or metallised label paper. Humidification of pressrooms is common in many print shops where there is focus on controlling variables that can influence productivity.

Fraser Anti-Static is a business that has developed, advanced, and proven techniques for overcoming quality and productivity problems caused by static electricity in digital, wide-format, commercial, label, and packaging printing.
It cites the common issues caused by static as: ghosting or overspray of ink; dust attraction to the media; static shocks to operators; print heads dropping out or becoming contaminated by ink mist; sheet feeding issues; and problems at the print finishing end of things.

Fraser Anti Static Techniques is based in Bampton, UK, and in 2016 celebrated its 25th year of continuous growth

Traditionally, AC anti-static bars and separate power units have been used to overcome such problems, but new 24V DC technology is gradually taking over. The 24V DC products have many advantages over AC, including more power, remote operation and monitoring, no high voltage cables, and no external power unit. Fraser’s leading Model 3014 is ideal for many print-focused applications.

For gravure printing and coating, the company suggests that its EX1250 Static Eliminator will be of particular interest. Its certification has been extended to include ethylene, MEK, and other group IIB gases. Fraser ATEX certified static eliminators allow the customer not only to run machines with greater safety, but also at much higher speeds. Recently a gravure customer in India was able to double the running speed of the printer after installing Fraser EX1250 bars.

One area which is increasingly used by printers, but remains problematic, is laser printing of high resistivity polymer sheets. Laser printing is not ideally suited to some polymeric media because the high voltage used in the process creates a double layer static charge on the sheet—positive on one side, negative on the other—which is very difficult to remove. The technical team at Fraser will be happy to give customers the latest thinking on these problems.

The Ionfix range of static generators from Fraser Anti Static Techniques has been designed for creating temporary adhesion

With this in mind, did you know that you can also use static electricity to improve your production process? Fraser’s Ionfix Compact Static Generator has been adopted by bindery machinery manufacturers to use static to hold and control signatures, magazines, and inserts in bindery and mailing applications.

Static and inkjet

So, with the groundwork now in place, it is important to consider how to improve static control with new technology. The printing industry is seeing inkjet evolve at quite a remarkable rate with no signs of stopping—increased speed and higher print quality machines are constantly appearing on the market. One unwanted result of these improvements will inevitably be a higher degree of static charge and contamination on web surfaces, leading to product cleanliness becoming an ever more noticeable issue.

In order to address this problem, web cleaning has to become a very important part of production, along with anti-static systems to help minimise such issues. So, touching on web-cleaning for a moment, it is vital for a full understanding of controlling variables in this area.

Iain Cameron, marketing director for Meech International, advises us that his company’s solutions are already well placed to provide the print industry and end users with the expertise required to keep things running productively: “Web cleaners and anti-static systems play an important role in helping companies achieve higher levels of productivity on their printing applications whilst minimising wastage. For these reasons, it is important for print businesses to capitalise on the strengths of these technologies that add significant value.

“For digital inkjet presses Meech employs both contact and non-contact systems for web cleaning on digital inkjet presses—these include the Tak Clean and the Cy Clean.

“Designed for narrower, slower presses, the Tak Clean has specially formulated elastomer contact cleaning rollers and perforated adhesive rolls, named Transk Taks. The Cy Clean is perfect for the newer, high speed presses. It can handle almost any substrate and has an optimised cleaning efficiency that allows for removal of contamination to below 0.5 micron. As more inkjet printable webs become available, the Cy Clean TM is a future proof solution.”

For static control on digital print lines, Meech offers its Hyperion range, featuring ionising bars that are fully compatible with most digital print lines. The 971IPS and 929IPS anti-static bars are two of the leading static solutions from Meech, providing efficient ionisation from a 24V power supply, they were developed as a response to customer feedback.

The 924IPS is the first, purpose built industrial 24V pulsed DC bar for short range applications and is the most compact pulsed DC bar available on the market. This makes it suitable for installation in challenging positions that would normally require an AC bar. The system employs the same four-pin M8 connector and shockless titanium emitter pins as other Hyperion bars.

O Factoid: Static can cause many problems in printing if not controlled including double sheets. This is when more than one sheet is fed into the mechanism, which can cause a jam. O

As for the continuing enhancement of its own products, Cameron adds: “To stay in touch with inkjet’s developments, we partake in discussions within the press manufacturers’ development sectors as well as our own customers. Based on the information we regularly receive, our technological advancements will go hand in hand with that of the print industry and continuing contact with those in the sector will allow Meech’s solutions to grow alongside it.”

Static and flexo

Lancashire-based print company Sturdy Print and Design has become one of the latest manufacturers to invest in Meech International’s static control solutions. The company has installed six 915 AC ionising bars in its flexographic department. The bars enable Sturdy Print and Design’s machines to perform at their optimum level, ensuring the safe and clean removal of static from their high speed web applications, resulting in higher quality print runs.

Meech’s Hyperion range features ionising bars that are fully compatible with most digital print lines

Founded in 1973, Sturdy Print and Design deal with all aspects of print, specialising in self-adhesive label production for packaging, including industries such as food, cosmetics, and pharmaceuticals.

Historically, Sturdy Print and Design has employed ionising bars for its web applications. It was a high demand flexographic run that required the web to be cleaned on a regular basis to eliminate contamination before the application of the ink that encouraged the company to invest in new anti-static bars. A visit from a Meech representative confirmed the current bars were positioned too close to the web to function correctly and that a technology upgrade would ensure optimum ionising performance.

The ionising bar that Sturdy Print and Design chose was the 915 AC bar, which provides effective ionisation up to distances of 150mm, even with fast web speeds, making it ideal for label production. The 915’s flexibility means the bar can be installed at the optimal position on the web.

Phil Cummings, operations manager at Sturdy Print and Design, explains: “Without Meech’s extensive consultation, the bars would not have been able to perform at their optimum. It was only when Meech rectified this that we noticed a huge difference in performance. The equipment functions that much better now that we have new bars that are set in the correct position.”

Sturdy Print and Design were so satisfied with the results, they have already made a further order of two more of Meech’s anti-static bars to be installed on their sheeters.

Cummings concludes: “I’m very happy with the quality of the product, the technical advice received before, during, and following installation. I can’t fault it, if I had to find a fault, I’d struggle.”

Adam Battrick, sales director at Meech International, says: “We are delighted to see the positive impact the 915AC is having on their business. We look forward to continuing to work with Sturdy Print and Design and to help them maximise the potential of their investment.”

Once again though, Meech explains anti-static technology is just one part of the equation.

The issue of web cleaning is becoming more important as the speeds of inkjet presses rise. Meech’s technical director, David Rogers, takes up the story: “The contamination could be dust from the production facility, slitting dust from previous slitting operations, loose papers fibres—especially when running recycled paper.”

With regards to why the print engine manufacturers themselves are not providing such solutions, Rogers suggests: “The OEM’s are in a price sensitive situation and need to keep their prices attractive. Whilst they do understand its importance, they typically prefer to offer static control and web cleaning as optional ancillary equipment.”

Rogers adds: “We have the widest range of web cleaners available from any one supplier. The styles are separated into contact and non-contact cleaning. In the case of the Tak Clean contact cleaner, we use special elastomer rollers to lift the dirt from the web. Whereas, the Cy Clean non-contact cleaner uses carefully controlled airflows to penetrate the boundary layer and remove contamination.”

Meech’s Cy Clean is perfect for the newer, high-speed presses

So, it is clear that these systems are integral in running a smooth operation, so why not take matters into your own hands and eliminate the chance of errors?

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