Effect of electrostatic assist and gravure process parameters on voids and dot skips reduction in shrink PVC film

Gravure is the most popular process used to print on shrink films for larger volume runs and high-quality reproduction. Polyvinyl chloride (PVC) holds the major share in shrink application. However, print defects such as voids and dot skips are the major concern while printing on shrink PVC film. The presence of these defects degrades the print quality and causes print rejections. The electrostatic assist (ESA) in gravure is designed to eliminate dot skips; however, the effect of ESA parameters such as air gap and voltage on print defects needs to be explored in depth. Thus, this study aims to minimize print defects by optimization of gravure process parameters. The study investigates the effect of process parameters such as line screen, air gap (distance between charge bar and impression roller), viscosity, voltage and speed on voids and dot skips. A general full factorial was designed and statistical model was developed to determine the influence of each process parameter on defect minimization. The results showed the significance of all the process parameters in reduction of dot skips and void area. The improved ink transfer with ESA resulted in elimination of dot skips and minimization of void area by 96%.