Recently, I visited a local customer to look at a specific application. This company prints over 146,000 different labels on plastic film, paper and foil. They called because they were seeing several different static related issues during printing and stacking processes.
On their first application, involving a 60″ wide sheeter, they were having an issue with irregularities as the sheet travels over several rollers where it enters the print head of the machine, then is cut and stacked. At the time of the visit, they were using a competitor’s product after the printer but those products were not effectively removing the static. We were able to determine they were not working by using our Digital Static Meter which told us there was still a 2.7 kV charge after the treatment area. I recommended the customer replace the ineffective units with our 60″ Ionizing Bar. The Ionizing Bar produces a bulk of positive and negative ions to eliminate the surface static of an object when mounted within 2″ of the surface of the material. The bar features a mounting flange that would allow the customer to use the existing bracket for easy installation.
The second machine we looked at was a 42″ 3-sheet press. Our readings ranged from 4.2 kV on the top sheet, 1.4 kV middle sheet and 9.9 kV on the bottom sheet going into the press/print head and around 15.6 kV at the discharge. This unit also had another anti-static device taped in place but was clearly no longer operational. I again recommend the Ionizing Bar for this application as well. After speaking with the operator, he was saying he was also seeing an issue with the sheets lifting and trying to separate as they were being stacked. To remedy this problem I recommended using our Super Ion Air Knife at low pressure to blow ionized air from behind the sheet to help it float onto the stack and remove static at the same time. The Super Ion Air Knife is our Super Air Knife with the Ionizing Bar attached and is capable of dissipating 5kV in less than half a second.
Lastly, we looked at their smaller sheeting machine and on this unit we were seeing around 3.5 kV as they stack was fed into the feeder and 7-8kV at the end stacker. At the beginning of the process we noticed the customer was using an air blowoff on each side of the sheet stack to assist with lifting and getting some separation between the sheets for the mechanical lifter to feed the machine. At this area they were experiencing some issues as occasionally the lifter would pick up more than 1 sheet and cause a jam which shut the system down. It turns out the airflow across the sheets was actually generating a slight static charge as we were seeing higher readings around 4.2 kV. Since they were already using air, I recommended replacing these blowoffs with our Ion Air Jet. This would aid in reducing the static and result in a more effective separation between the sheets allowing for a cleaner lift. For the sheet itself, we would recommended the Ionizing Bar if they were able to mount within 2″ or the Super Ion Air Knife for further mounting distance.
We realize we can’t look at every customer’s process but any photos or videos you could share of your application, we would gladly review and make a possible recommendation. Please contact one of our application engineers for assistance.
One of the big issues in winter many manufacturing and process industries experience is static. An outside sales rep who was responsible for selling and servicing industrial laser printers contacted us after he started to receive more complaints about the quality of the print, especially with customers that used polyester sheets. One of their customers was printing both sides of a 13” X 19” (33 X 48 cm) sheet, and they noticed that the print on the back side was blurry. We discussed how static can cause issues like this in printing applications. A static charge can keep ink from landing in the proper location, it can cause ink to spiderweb, spread over defined boundaries or fail to penetrate its target.
Being that EXAIR Corporation is a leader in production and application of active Static Eliminators, we were able to discuss the issues and suggest some possible solutions. Laser printers are designed to use static to pick up toner onto a drum and to apply it to sheets of paper. If the sheet of paper has a charge on it, that can affect the print quality because like charges repel each other. In this application, we have two conditions that contributed to the increase in static charge on the polyester sheet, the dry air and the type of material. Dry air in winter is pretty much a given as cold air cannot hold as much moisture as hot air can. With a decrease in moisture levels, static fields can build to much higher levels causing discharges, the small “shocks” you experience when you touch a non-conductive material, another person or even a grounded machine. The other static issue is material. The type of materials involved in an application determine how they will share electrons when they rub together. Some materials give up electrons readily and some materials tend to gain electrons.
Getting back to the application; inside the mentioned printer, a rubber roll was used to invert the paper to print on the back side. If the paper was cellulose, it is harder to generate static as the rubber roll and cellulose are similar in sharing electrons. However, this sheet was made of polyester, it has a higher affinity to take electrons from the rubber roll. A static field would build which was enough to affect the transfer of toner from the drum causing a blurred image.
Our strategy for applying static elimination solutions is to determine the point of static generation and locate the static elimination equipment just downstream of the problem area. In this instance, it was after the roller just before printing. The space was limited, so the customer went with model 7012 Ionizing bar with the 7901 power supply. The positive and negative ions that are emitted from the Ionizing Bar will neutralize static fields of positive or negative polarity bringing the surface of the polyester material back to neutral. The length of the bar was slightly shorter than the width of the sheet, however it still has plenty of capacity to neutralize the outside edges. The end user mounted the Ionizing Bar in the center of the sheet about 0.5” (13mm) away from the surface. After he plugged in the Ionization Bar, the static field was removed and the printing on the back side was now clear. The end user was so impressed that he contacted the manufacturer of the laser printer to suggest they add effective static elimination as an option for troublesome applications like his.
If you have static issues and you want to remove the pain they cause in the form of injury, lost production time and material waste, contact EXAIR and speak to one of our experienced Application Engineers.