Shocking Solutions

Static has a knack for wreaking havoc on even basic printing applications. Here, suppliers offer a range of remedies.

by Kate Tomlinson, Assistant Editor

WHAT'S YOUR WORST static nightmare? Several package printers recently shared theirs with packagePRINTING. They follow below, along with static control suppliers' strategies for remedying the issues at hand.

Static Attack #1: Is it slowing you down?

Problem: "We found that especially while working with sheeted polystyrene or clear BOPP, we were having a lot of trouble stacking and jogging the product as it came off the press. Due to all the static these materials hold, we were only able to run the press at 110 fpm. We also received feedback from our flexible packaging customers that they were able to increase line speeds due to a reduction of static in the product."

—Jeff Vincent, process improvement manager, Belmark, Inc., pressure-sensitive tags/labels and flexible packaging converter

Solution: "Utilizing our experience on static control for winding applications, Ion Systems initially worked with Belmark to determine the proper location and installation of the Virtual AC Intelligent Static Neutralizer systems for their film rewinders. This technology provided more ions to reach greater distances.

Static charge accumulates as incoming material winds into a roll. In order to get a neutral roll at the end of the winding cycle, every layer of the material in the roll must be neutralized. Thus, static neutralizing bars must have long range capabilities in order for the bar to clear the diameter of the finished roll and still effectively neutralize the material as soon as it starts winding on the core.

The Virtual AC technology was also used to neutralize the labels after being die-cut on the film press to reduce stacking and jogging problems. In addition, real-time feedback of system performance and operational status has contributed to better productivity and quality production. The results were a dramatic reduction of static charge on the processed material. Adding static control equipment to Belmark's machinery has provided numerous benefits: finished customer products are now neutralized; operators receive a decreased number of shocks while handling finished rolls; electrical malfunctions (such as control lock-ups) are decreased; and press speeds have increased from 110 fpm to 250 fpm."

—Bill Emmes, sales manager, Ion Systems

Static Attack #2: Are sparks flying?

Problem: "Because of the structure of some of our products, we have experienced numerous problems with static. The paper, poly, foil, poly structure of our pre-laminated web creates a capacitive effect each time it passes through a nip. The potential created is enough to jump through the outer poly layer to a grounded surface. This has caused us to perform many repairs to our electron beam curing ovens, due to damage to the titanium foil separating the vacuum enclosure from atmosphere.

The static has also damaged the impression cylinders on our printing cassettes. The sparks jump from the edge of the web to the cylinder, creating arc marks on the surface of the cylinder. We are currently using stainless steel brushes to touch the sides of the web to dissipate the static potential at each print tower as it leaves the nip. If suppliers have any more ideas, please let me know."

—Charlie Grant, electric lead man, Amgraph Packaging, flexible packaging converter

Solution: "This is truly one of the toughest static-related problems to solve. A sandwich of insulative materials with conductive materials (the foil), in essence creates a capacitor, which Grant referred to as a capacitive effect. This means that no field exists and the voltage that caused the static discharge is trapped between the layers. A fieldmeter would not be able to measure the voltage, due to the collapsed field.

Static fieldmeters are designed to read fields of static coming off a particular substrate. These fields are reduced by static control equipment such as bars, blowers, and other electrical devices. When no field exists these conventional types of ionizers will not work. Whenever possible, the static on the individual materials making up the sandwich should be reduced to relative zero before the lamination occurs.

After lamination, when standard equipment is virtually useless, the best method to use is already being deployed. Stainless steel brushes used as grounding devices can take the discharged voltage to ground by providing a path of least resistance. Without the stainless steel brush, the damage to the printing cylinder, e-beam oven, and the finished goods would be much greater.

While fieldmeters cannot read the energy on the sheets or web with this capacitive configuration, there are voltmeters that can give exact reading of what is going on in the substrate. We offer the Model 244 Electrostatic Voltmeter which is great for those who coat plastic webs with foil to make barrier films and materials, as well as manufacturers of photographic films."

—Jim Patterson, executive vice president, Julie Industries

Static Attack #3: Is it affecting your end product?

Problem: "During the humid summer months, static is virtually a non-issue. Our plant is climate controlled, but that extra bit of humidity in the air keeps our static down. In the winter months, static can be present in the raw materials from our suppliers and can build up on the substrate, especially after contacting the metal rollers in the press. Static build-up attracts dust, affects ink laydown and can cause an annoyance to our press operators and end customers. Our presses have web cleaners, corona treaters, and static eliminators at the beginning of the press, but static can be re-introduced to the web after just one roller.

We have tried a variety of static eliminators and find that tinsel works very well and is an affordable way to address the problem. We also use a variety of 'off-the-shelf' products, but these units can get in the way of the operators, malfunction, or simply be too difficult to install and maintain after every roller. Perhaps suppliers can recommend an operator-friendly solution that will stay within my budget."

—Dave McKell, director of operations, Spear, pressure-sensitive film label converter

Solution: "It is true that static charges are generated on the web as it contacts the many idler rolls in a web press, but attempting to control the charge after every idler roll would be overkill and unnecessary.

The best approach is to have a qualified static control field specialist evaluate the press, take static measurements on the web, and recommend the best product to solve the problem. Shockless static bars are the most cost-effective, reliable solution. They are very small and require very little maintenance. They are permanently installed, can last for several years, and have no safety issues.

The type of press and the static-related problems typically experienced will dictate how many static bars are required and where they should be positioned. The static field specialist can provide this guidance."

—Scott Shelton, N. American sales manager, SIMCO