In-Roll Stress Analysis Considering Air-Entrainment at the Roll-Inlet with the Effect of Grooves on Nip Roll Surface

Abstract

High-speed winding of paper web sometimes leads the winding system into unstable states, interlayer slippage of wound roll, paper breakage and so on, due to the excessive air-entrainment at the roll-inlet of nip contact region. These phenomena are more frequently observed on coated paper or plastic film comparing with newspaper, because the former allows little permeation of air and their surface roughness is small. Therefore, it is of vital importance to clarify the in-roll stress of wound roll considering the effect of air-entrainment. Generally, it is known that the amount of air-entrainment is affected by grooving shape of nip roll surface. In this paper, we focused on the grooving shape and investigated the relationship with the air-entrainment into two rolls being pressed each other and the grooving shape in order to achieve stable winding at high speed. We conducted experiments using small sized test machine. Entrained air-film thickness was evaluated applying the solution of the elasto-hydrodynamic lubrication for foil bearing with the consideration of nip profile at the grooved area. Air film thickness was measured to ensure the applicability of the above theory. Consequently, we found that the air film thickness can be estimated considering the effect of grooves on the nip roll surface, and that the validity of the above estimations was ensured from experimental investigations. Furthermore, it became to be able to propose the optimal shape of grooves on nip roll surface to maintain the stable winding at high speed and at large-diameter in reel.

Non-destructive inspection of film-winding conditions via three-dimensional visualization of in-roll structures using optical coherence tomography (A feasibility study)

“…This study focused on structures of film rolls visualized by OCT, but functional OCT can detect 3D distributions of mechanical properties of samples such as elasticity, strain, and stress (Wang and Larin, 2015;Sakata Y et al, 2010;Oh and Kim, 2003). Since these mechanical properties relate to the occurrence of defects in film rolls (Tanimoto et al, 2002;Sasaki et al, 2008;Kanda and Hashimoto, 2012), mechanical information detected with functional OCT will not only contribute to improving the inspection accuracy but also predict and prevent the occurrence of defects in film rolls.…”

“…5i). These air gaps were not the defect but may affect the in-roll stress causing defects (Tanimoto et al, 2002;Sasaki et al, 2008;Kanda and Hashimoto, 2012;Hashimoto and Sunami, 2015;Hashimoto and Sunami, 2016), and therefore detection of air gaps with OCT will also contribute to improving the inspection of film-winding conditions.…”

“…As described above, air gaps in film rolls relate to film-winding conditions since they may change the in-roll stress during film-winding (Tanimoto et al, 2002;Sasaki et al, 2008;Kanda and Hashimoto, 2012;Hashimoto and Sunami, 2015;Hashimoto and Sunami, 2016). Hence, we further analyzed OCT images for each film roll sample to detect the area of air gaps quantitatively.…”

Optimum Winding Tension and Nip-load into Wound Webs for Protecting Wrinkles and Slippage

“…The generation of wrinkling and slippage in the wound roll is strongly related with the in-roll stress distributions in the wound roll; therefore, it is necessary to understand well the background about stress distributions inside the wound roll. In the past, some researchers investigated theoretically or experimentally into the in-roll stress distributions in the wound roll (1)(2)(3)(4)(5)(6)(7)(8) .…”