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.
John Ball, Application Engineer
E-mail: johnball@exair.com
Twitter: @EXAIR_jb
