A: As we progress into the fall and winter months with the onslaught of colder, lower-humidity weather, the conditions for the generation of static electricity in flexible film processes increases significantly. High humidity environments are less conducive to the generation of static electricity whereas dryer, lower-humidity conditions act to greatly encourage the creation of static.
Static electricity can generate anywhere there is contact and separation or friction between the materials being processed or between the film and rollers, guides, etc. It is common to see static charges accumulate in typical manufacturing processes to values of 15,000 volts to 35,000 volts. In some applications such as high-speed film, winding voltages in excess of 75,000 volts can be present.
The primary issues:
Lower Production: Static can create a situation where a particular flexible film process cannot run at its optimal speed due to clinging of the materials to itself, feed, or conveyance components. In some cases the machine process will not function at all in the presence of moderate static charges.
Quality Impairment: As the level of static increases, more and more contamination will be drawn from the surrounding environment and will be electrostatically bonded to the film. This can cause defects and rejects in sealing, laminating, and winding operations. Static can cause imperfections when printing on films, as ink follows the electrostatic field pattern on the surface of the film causing poor printing impressions.
Personnel Shock: Shock from static discharge can be a significant concern. Static shock can range from mere discomfort to a very painful experience for anyone handling film products, such as a highly charged film rolls. In addition, there is a hazard factor due to a person's recoil response from a static discharge when working around sharp or moving machine parts.
A: A classic example of static issues in flexible film would be a roll winding process. Because of static attraction, the film may not wind properly on the roll producing telescoping and baggy areas. Also contamination attraction due to static charge can cause trim, airborne contaminates or excessive slitter dust to be wound into the roll. Furthermore, the accumulating static charges between each layer of film as it is being wound builds the level of static charge potentially to the point where handling or even being in close proximity to the roll can cause a painful static discharge for production floor personnel. Other undesirable consequences of uncontrolled static electricity is its tendency to interfere with or cause serious damage to sensitive electronic web controls, such as defect detection cameras, web edge sensors and other high-value electronic controls that are installed along a web’s path.
Lastly, a sometime overlooked, but very important issue is that if the roll is being sent to a customer for further processing, the static remains in the roll. When the customer attempts to process the roll, they will likely encounter multiple static-caused production issues, resulting in customer dissatisfaction.